On the New Zealand Lamprey, Geotria australis Gray. Part 1.—Biology and Life History. By F. G. Maskell, B.A., M.Sc., Lecturer in Zoology, Victoria University College, Wellington, N.Z. [Read before the Wellington Philosophical Society, 28th November, 1928; received by Editor, 19th February, 1929; issued separately, 31st May, 1929.] 1.—Introduction. This paper is the first of a series of studies dealing with the New Zealand lamprey—Geotria australis. In it will be discussed the Biology of the lamprey and the stages in its life history. The second paper will deal with the mid-gut diverticula, structures peculiar to the ammocoetes stage of Geotria. Below is given a short history of work, which has dealt with the New Zealand lamprey. “Both the Velasia stage and the adult Geotria were first described by Gray in 1851 and were classified by him as distinct genera (Geotria and Velasia) of the family Petromyzonidae. Günther in 1870 ranks the two forms as separate species of the genus Geotria; the pouched form he calls Geotria australis, and the Velasia he calls Geotria chilensis, since Geotria in the Velasia stage was first discovered in Chili.” I have not had access to Gray's paper, hence the above extract from Dendy and Olliver (1902). It is interesting to note that Günther (1870) is already doubtful of the specific distinctness of these two species. He says (p. 509) “Philippi (Wiegm. Arch. 1857, p. 266) has described a lamprey from Chile under the name of Velasia chilensis; the example was provided with the sac at the throat, and the description agrees with Geotria australis, so that we must assume either that this latter species occurs not only in Australia, but also in Chile, or that Velasia chilensis at a certain stage of development is provided with a gular sac. If the latter be the case, the specific distinctness of the two fishes would be questionable. The form of the mouth of the example seen by Philippi, and figured in Wiegm. Arch. 1863, taf. 10, fig. a, is exactly intermediate between that of the mouth of the types of Geotria australis and Velasia chilensis.” Hutton (1873) lists and figures as two separate species Geotria chilensis and Geotria australis. Ogilby (1896) returns to Gray's system, again making two independent genera, Velasia and Geotria. Smitt (1901) in describing a lamprey from the Rio Gallegos, South America, which he names Geotria macrostoma forma gallegensis, has the following significant paragraph “C'est un plus-ou-moins du développement des cartilages et de la substance cornée du měme type. Si ľon places les espèces décrites dans ľorde suivant: Velasia chilensis, Geotria australis, Exomegas macrostomus, et enfin notre exemplaire, on voit une série continue de développement de ce plus-ou-
moins.” Dendy and Olliver (1901) were the first to show that the forms without a pouch, which they speak of as at the Velasia stage, were sexually immature, while the only two pouched forms which they possessed were sexually mature or nearly so. They ascertained that the teeth of the two forms correspond in number and position, though the labial teeth of the pouched form are further apart owing to the growth of the disc between them. Finally, they recognise therefore only one species in New Zealand, Geotria australis, with three stages in its life history, namely, Ammocoetes stage, Velasia or sexually immature stage, and adult (pouched) stage. Plate (1897) described as a new genus and species from Chile, Macrophthalmia chilensis, which form he later recognised as a young stage (after metamorphosis) of his Geotria chilensis. In 1902 Plate published a systematic revision of the Southern hemisphere lampreys. Of the seven genera previously recorded from the Southern hemisphere he allows only three to stand—Geotria, Mordacia and Exomegas. Under Geotria he makes three species, chilensis, stenostomus and australis, but he himself remarks on the insignificance of the specific characters separating them. From the description and figure, I fail to see how stenostomus differs from chilensis in characters sufficient to give it specific rank. I do not consider stenostomus can stand and believe it should be included under chilensis. Waite (1901–3) quoted by Woodland (1914) states it is difficult to know in what essentials stenostomus differs from chilensis. This leaves chilensis and australis. Dendy and Olliver (1901) have shown, and this paper will further show, that these two represent different stages in one life-history. There exists, therefore, in New Zealand only one species of Geotria—Geotria australis Gray. Probably this is also the case for Australia, Tasmania and South America. As to the genus Exomegas, it appears that this will not stand examination either. In this connection I refer again to the extract from Smitt (1901) quoted above. Further Lahille (1915) says “El género Exomegas es uno de los tantos nombres que hay que suprimir de una vez de la sistemática, y hay ostros zoólogos quienes piensan lo mismo como yo. Smitt, por ejemplo hablando de los caracteres de Exomegas y Geotria, dice con razón que no corresponden, à divergencias de forma, pero si a simples grados de desarrollo, y que no merecen por cierto ser utilizados para establecer divisiones genericas” and again “Se puede decir que los ejemplares que se obtienen, se determinan como Geotria australis cuando se encuentran en los rios del centro y del sur de Chile o bien en Australia. Reciben, al contrario, el nombre de Exomegas macrostomus cuando se obtienen en la Patagonia argentina desde el río Gallegos al rio Colorado y aun hasta el rio de la Plata o la isla de Flores (Republica Oriental del Uruguay)!” Plate (1902) does not discuss Exomegas. Finally, the genus Mordacia is credited with three species. Of this genus I know nothing, since it has never been reported in New Zealand. This appears strange, since its occurrence is reported in Australia, Tasmania and Chile. Regan (1911) recognises two Southern hemisphere genera—Mordacia and Geotria. Exomegas is placed as
a synonym under Geotria. But under Geotria he actually lists five species—chilensis, stenostoma, saccifera, australis and macrostomus. But the characters used by him as specific will not bear examination in the light of a knowledge of the life history of Geotria. These characters are nearness or spacing of the labial teeth—presence or absence of gular pouch—smallness or largeness of disc—two cusps or three cusps on anterior lingual lamina—small changes in relations of fins—small changes in cusps of supraoral lamina. Dendy and Olliver (1901) had already shown that certain of these characters were liable to change at different stages in the life history. This phenomenon will be discussed and confirmed more fully in this paper. The latest paper dealing with the Southern hemisphere lampreys is that of Lahille (1915). He concludes, “Creo, sin embargo, y sin hacerme ilusion sobre el valor de la palabra especie, que se pueden considerar como distintas especies à G. chilensis y a G. australis,” and then follow his reasons, which briefly are—(1) differences in length of the two forms; (2) differences in height of the two dorsal fins; (3) differences in the interval between the dorsal fins; (4) differences in the interval between second dorsal fin and caudal fin; (5) differences in the relation between the length of the snout and the length of the head. These differences exist, but they characterise different stages of the life history and are to be explained as a result of the shortening which almost certainly takes place with the approach of and during sexual maturity. Phillipps and Hodgkinson (1922) among the edible fishes of New Zealand list the lamprey—one species —Geotria australis. In a later paper, Phillipps (1927) lists two species of lamprey—Geotria australis—Southern lamprey, and Geotria saccifera—Northern lamprey. In a still later paper, however, Phillipps (1927A) lists only one species—Geotria australis. As I have indicated above, and as I hope this paper will show, a careful study of the life history justifies the statement that there is only one species of Geotria in New Zealand—Geotria australis. During the course of this work, I received two important papers by Cotronei, which have considerably influenced my opinions. The first (1927) dealing with the insular organ of Petromyzon, will be discussed later when treating of a similar organ in Geotria. The second (1927A) and a previous note of his (1926) suggested the clue to facts, which have puzzled most students of the species of Geotria—namely the differences in total length of the forms studied and the differences in the intervals between the fins. In his paper Cotronei showed and was able to verify experimentally, that in the species studied by him, sexual maturity is accompanied by a process of shortening, and by changes in the intervals between the fins. His work will be referred to more fully in the text. I take this opportunity of expressing my thanks to the following gentlemen for their invaluable assistance: Mr. W. J. Gray (Okato), Mr. B. C. Lysaght (Hawera), Mr. T. W. Downes (Wanganui), Mr. L. S. Mackie (Otakeho), Mr. Topine Ngatai (Taumaranui), Mr. R. Hatrick (Wanganui), and to Professor H. B. Kirk. I feel par-
ticularly grateful to Mr. Gray and to Mr. Lysaght for the trouble which they have taken to assist me in this work. 2.—Summary. 1. Only one species of lamprey is found in New Zealand rivers—Geotria australis. 2. The following stages are to be distinguished in the life history—(1) Ammocoetes stage—found in sandy patches along the banks of rivers. (2) Macrophthalmia stage. By this is understood the completely metamorphosed Ammocoetes while still found in fresh water. It resembles the Velasia, except for size. (3) Then follows a period of life in the sea, when nourishment is obtained, no doubt, in the “semi-parasitic” fashion characteristic of lampreys, i.e, by attaching themselves to other fishes, rasping a hole in their skins, and sucking the blood and other juices. We have no direct observations on this period. It is probably quite long. (4) Velasia stage. The lampreys, after their life in the sea, enter the rivers, which they ascend in shoals. They have reached their maximum growth, are in tip-top condition and suitable for eating. From the time of entry into the rivers, a very gradual decline, to be associated with the ripening of the sex glands, sets in. To the best of our knowledge, the lamprey feeds no more. (5) The adult stage or stage preceding and during sexual maturity, passed through in the upper reaches of streams and rivers. The male develops a remarkably enlarged oral disc and pouch, while these are only just indicated in the female. It is almost certain that both sexes undergo shortening in this stage—reduction taking place largely in the tail region with consequent alterations in the distances between the various fins. These various stages are described below. 3. The building of nests and the spawning process have not yet been observed. 4. A pouched lamprey caught in the Makara stream on 9th October, 1927, has been kept alive in a tank without food since that date. He has fasted thus for a year and five months, and is still alive. 5. The smallest Ammocoetes yet found measure 1.1 cm. long. 6. Ammocoetes undergoing metamorphosis may be found during January and February. 3.—Ammocoetes Stage. a. Historical. b. Occurrence, Mode of Life, Size and Metamorphosis. c. Description of a 1.2 cm. Ammocoetes. d. Description of older Ammocoetes. a. Historical. Originally, the larval form of the lamprey, on account of the striking differences which exist between it and the adult form, was described as a separate genus under the name of Ammocoetes.
In 1666, L. Baldner, a fisherman of Strasbourg, stated that the young, which hatched out the eggs of the lamprey, were blind, and that these young did not spawn till they became seeing (“bis sie gesehend werden”); the blind and the seeing are therefore of one species (“einerley Art”). In 1885, M. Schultze, saw that from the lamprey spawn arose animals with eyes lying deep under the skin and an upper lip enclosing, guard like, the lower, while in 1856, Aug Müller traced the metamorphosis of the Ammocoetes or larval form into the adult lamprey. Since then, the lampreys of the Northern hemisphere have been the subject of numerous and important investigations. On the other hand, comparatively little work has been done on the Southern hemisphere lampreys. Reference below is made only to papers which deal with the Ammocoetes stage of the latter. Kner (1869) briefly described the external features of an Ammocoetes of two and a half inches length, which Dr. Hochstetter brought from Taupiri, Waikato, Auckland, New Zealand. Descriptions of two Australian specimens, Neomordacia howittii Castelnau and Yarra singularis Castelnau are to be found in Macleay (1882). Ogilby (1896) considers these as young forms of the narrow-mouthed lamprey, Velasia (Geotria) stenostomus, Plate (1902) as young forms of this species or of Geotria chilensis. Plate (1897) described as a new genus and species from South America Macrophthalmia chilensis, which was later recognised as a young stage of Geotria chilensis. Smitt (1901) describes a number of fresh-water fishes collected from Patagonia in 1898–99 by E. Nordensköld. Amongst these was a single adult lamprey, “mais un grand nombre de larves (Ammocoetes) de la lamproie de Rio Gallegos et de ses affluents, Rio Ruben et Rio Turbio.” He remarks on the difficulty of distinguishing these from the European Ammocoetes, the easiest distinction probably being in the number of preanal myomeres, more than eighty in the South American Ammocoetes, while they are less numerous in the European forms. He figures a specimen of three and a half inches length, and regards these Ammocoetes as of the same species as the adult, Geotria macrostoma, forma gallegensis, both being collected in the same locality. Plate (1901, 1902) describes some Ammocoetes stages of Geotria chilensis, the youngest being seventy-six millimetres long, the oldest, which have evidently undergone metamorphosis, being from one hundred and seven to one hundred and eighteen millimetres long. Dendy (1902) states “The Ammocoete of this interesting species (Geotria australis, the New Zealand lamprey), is known to us only through two specimens: one of these was briefly described by Kner (1869); the other was for many years in the Museum of the Otago University, Dunedin, and was forwarded to me for investigation by the present curator, etc.” According to the label it was caught in the Opoho Creek in January, 1884. Dendy sectioned the head region, being then engaged in an investigation of the parietal organs in the adult. Thus, very little indeed is known about the New Zealand Ammocoetes, and it had come to be considered as very rare and difficult to obtain. Three years ago, about the beginning
of 1926, the writer commenced an investigation into all stages possible of the New Zealand lamprey, Geotria australis, and the results, so far as regards the Ammocoetes are given below. b. Occurrence, Mode Of Life, Size And Metamorphosis. Ammocoetes of the New Zealand lamprey have been collected in the following rivers: Ongarue R. at Taumarunui, a distance of about one hundred and fifty miles from its mouth at Wanganui, Kie-hi-hi and Kati-kara rivers in Taranaki, Waikanae, Hutt and Makara rivers in Wellington, Ruamahanga and Waipoua rivers in the Waira-rapa district. Probably they are present in nearly all the New Zealand rivers. They live in sandy spots and shallows at the banks of the rivers. Fine mud to sand, or a mixture of these two, appears to form the most suitable home for the Ammocoetes. They are not found in stiff clay, nor usually in gravel, though sometimes the larger specimens may be found in gravel. Such sandy spots as house the Ammocoetes may be found along the banks or in small backwaters of the rivers. Frequently these spots are covered with fallen leaves, twigs, debris, etc., lying on the surface of a shallow pool or on the sand itself. The Ammocoetes may be in the sand covered by the pool or washed by the running water or frequently in the sand just at the junction of bank and water. In Taranaki many dams have been built on the numerous small streams which exist here, in order to provide a source of power for the dairy factories and farms. The races, which lead the water from river to factory and thence back to the river, are periodically cleaned out to remove the sand, mud and vegetation which accumulates in them. The Ammocoetes, or “elvers” as they are sometimes erroneously called, are said to be abundant in the sand, mud, etc., in these races, but I have never been present at the cleaning of one. The Ammocoetes live buried in the sand at a depth varying from about three to nine centimetres. The best way to obtain them is to wade in the river and provide oneself with a bottle or tubes and a biscuit tin or half a kerosene tin cut so as to form a scoop. A likely-looking spot is then selected and the sand scooped up and thrown on the bank, the fingers passed rapidly through the sand to break it up, when the Ammocoetes, if present, are seen and further reveal themselves by their energetic squirmings and wrigglings on finding themselves out of their natural medium and in the light of day. Once seen, the Ammocoetes must be immediately secured, as they can burrow with remarkably rapidity, while their squirmings may precipitate them back into the river, particularly if one is working against a steep bank or in cramped surroundings, as is frequently the case. An ordinary jam or preserving jar serves to carry the Ammocoetes in, and a layer, four to six centimetres thick, of the sand in which they were found should be placed in the bottom of the jar, so that they may bury themselves in it. Summer and Autumn are the best seasons for collecting, since the rivers are low and many sandy spots and shallows are exposed. When the rivers are flooded it is difficult or sometimes impossible
to reach suitable spots. When the laboratory is reached the specimens may be placed in dishes of water for a preliminary selection, examination, etc. They are extremely restless and uneasy, when thus exposed to the light with no sand to burrow in. They swim about energetically, until apparently temporarily exhausted, when they rest on their sides at the bottom of the dish. If such a one, resting on its side, be now examined, with the naked eye or with a lens, the movement of the velum is strikingly exhibited as also the alternate contraction and expansion of the branchial region. If it be desired to keep them alive, this may be done by means of a small aquarium. A tank, in which about twenty Ammocoetes of varying sizes have been kept for a year, holds about twenty litres of water, has a layer of sand and mud on the bottom collected from a spot in which Ammocoetes were found, about four centimetres deep, and some pieces of water-weed. No running water is necessary—the Ammocoetes are thus no trouble to keep. They do not show themselves during the day, but sometimes come out at night. If one day the surface of the sand be smoothed, the next day small holes will be seen in it and also grooves or furrows on its surface. Sometimes, though rarely and not for long, the head and branchial region may be seen projecting from the sand. Another point which would strike even the most casual observer of a living Ammocoetes is the white shining brightness of the pineal eye. In small specimens of about one and half centimetres length, the gall bladder may be seen through the body wall on the right side filled with a green fluid—the bile. The smallest Ammocoetes yet found in the rivers measured 1.1 cms. long. In a sandy backwater of the Katikara River in January, 1928, specimens varying from 1.1 cms. to 1.6 cms. were fairly abundant and about thirty were collected, but though this spot and adjacent likely spots were carefully examined, I could not find any smaller ones. In the Waikanae River in the same month I found a single specimen, 1.2 cms. long. In June, 1928, that is four and a half months later, another single specimen of 1.2 cms. length was also found in the Waikanae River. Metamorphosis of the Ammocoetes occurs usually when they have reached a length of about 10 cms. but I possess specimens which were undergoing metamorphosis when only 8.7 cm. long. (Kie-hi-hi River—February, 1927). Metamorphosis may thus occur when the Ammocoetes are somewhat shorter. In January and early February of 1928 specimens undergoing metamorphosis were found in the Hutt and Waikanae Rivers, but none which had completed metamorphosis. In late February, while specimens still undergoing metamorphosis were found, completely metamorphosed specimens (Macrophthalmia) were also found. These latter were also obtained in March. In June I could find no Macrophthalmia stages. In 1927, Macrophthalmia stages were collected in late February, March and April. It appears probable, then, that Macrophthalmia (the completely metamorphosed Ammocoetes) goes down to sea about May or June.
c. Description of a 1.2 cm. Ammocoetes If a 1.2 cm. Ammocoetes be placed in a small glass tube filled with water, it may be examined alive under the binocular. The activity of the velum and the pulsation of the branchial region are shown strikingly, the pulsation of the heart more faintly. The large upper lip is very pliable and strong and must form an efficient organ for burrowing in the sand and mud. The nasal aperture and pineal spot are situated in an area of skin (roughly diamond shaped), from which pigment cells are absent. The nasal aperture appears oblong to slit-like in shape, the pineal spot is circular, bright white and shining. This pineal spot, is very conspicuous in the living Ammocoetes, whereas in the preserved specimens it cannot usually be made out at all. The eyes are visible as two black spots, a short distance behind and below the pineal spot. Behind these, the two auditory capsules can be made out as large white oval structures. Beneath the first four gills, the right and left halves of the thyroid show clearly, one on each side of the mid-ventral line. In a side view of the branchial region, the gill lamellae show. The gill pores open externally into a longitudinal gill furrow. This furrow can be closed or opened—in preserved specimens it is usually more or less closed. At this stage the gall-bladder is relatively immense and can be seen from the right side or from the ventral surface. It shows through the body wall as an oval bladder, distinctly green, since it is filled with a green fluid, the bile. In the mid-dorsal line, starting at the level of the second gill, there runs a low ridge—posteriorly this passes into the dorsal half of the caudal fin. In the mid-ventral line, a similar ridge runs from the posterior end of the branchial region to the cloacal aperture. Behind the cloaca is the ventral half of the caudal fin. Under the binocular, these ridges and the caudal fin appear quite transparent. Pigment cells are abundant on the upper lip and numerous on the dorsal and dorso-lateral body surfaces. They are absent or rare in the skin on the ventral and ventro-lateral surfaces, but in the living animal the pigment cells in the peritoneum show through the transparent body-wall in these regions. Pigment cells are absent from the dorsal and ventral median ridges and the caudal fin. d. Description Of Older Ammocoetes. Dorsally and dorso-laterally the colour in life is dark brown to brown, and ventrally a light brown—the gill region appears reddish. In formalin specimens this colouring is lost, the dorsal Fig. 1.—Ammocoetes stage, 8.4 cm. and dorso-lateral surfaces being gray and the ventral surface pale. A pale white streak runs down the mid-dorsal line. The first dorsal fin is not evident in a 1.2 cm. Ammocoetes. It is present in a 3.3 cm.
as a very low ridge, not visible however to the naked eye. The caudal fin in Ammocoetes (of lengths up to about 6 or 7 cms.) extends, both dorsally and ventrally, to the level of the cloaca. In specimens of about 7 cm. and over, however, it is noticed (Fig. 1) that ventrally, the caudal fin no longer reaches to the cloaca, but only about half-way there, while in Macrophthalmia (Fig. 2) the caudal fin, both dorsally and ventrally, extends only about a third of the distance from the tip of the tail to the cloaca. The dorsal half of the caudal fin in the Ammocoetes contains in itself, as Plate (1902) remarks, the anlage of the second dorsal. Not until the metamorphosis is the second dorsal completely marked off as such. In an 8.7 cm. in metamorphosis, a notch marks off the posterior limit of the second dorsal, which is still, however, continuous with the caudal. This notch is indicated earlier—it may be noticed, on careful examination, in specimens of 6.5 cms. Fin rays can now be seen with a lens in the fins of the 8.7 cm. specimen. In a 10.4 cm. in metamorphosis the same condition of affairs holds. In Macrophthalmia the second dorsal is separated from the caudal by a space (Fig. 2). In the Ammocoetes there is a dark streak along Fig. 2.—Macrophthalmia stage, 10 cm., coloured bands not shown. each side of the line of attachment of the first dorsal, and also alongside the anlage of the second dorsal, so that, even in the Ammocoetes, the extent of the second dorsal is indicated. Throughout the Ammocoetes stage the first dorsal remains as a low ridge. The nasal aperture in preserved specimens is triangular—the base of the isosceles-shaped triangle being posterior. The aperture is surrounded by a distinct wall, projecting above the level of the surface of the body. The longitudinal gill furrow into which the gill pores open and the clear area of skin in which are situated nasal aperture and pineal spot have already been mentioned in describing the 1.2 cm. specimen. The upper lip is large, hood-like and horse-shoe shaped, enclosing with two lateral lobes the smaller lower lip. The cavity enclosed by the lips is referred to by Rathke as “Mundhohle.” It is limited posteriorly by a transverse ridge, from which spring a number of branched tentacles, the tentacle in the mid-ventral line being the largest. A small triangular area on the under surface of the upper lip also bears small tentacles. Behind the “Mundhohle” follows a second cavity, the “Rachenhohle” of Rathke. This second cavity is limited anteriorly by the circlet of tentacles already referred to, which form a guard of filter at its entrance. Posteriorly the “Rachenhohle” is limited by the two velar folds. Between the velar folds is the entrance to the pharynx or “Kiemenhohle.” Under the binocular some of the lateral line organs on the upper lip and
head may be observed. In some Ammocoetes the pineal spot lies not in the middle line, but slightly to the left. Smitt (1901) referring to the South American Ammocoetes described by him, says “La plus facile distinction se fera probablement par le nombre des Myomères préanales, plus que 80 chez les Ammocoetes américains, tandis qu'ils sont moins nombreux chez nos Ammocoetes.” I find that Smitt's remark will apply also to the New Zealand Ammocoetes—in all specimens over 3 cms. long examined the number of pre-anal myomeres is more than 80. Some Ammocoetes chosen at randon show the following numbers: Length of Ammocoetes. No. of pre-anal myomeres. 3.6 cm. 90 4.7 cm. 90 5.8 cm. 95 7.8 cm. 92 8.8 cm. 91 Length of Macrophthalmia. 10.8 cm. 95 9.0 cm. 90 4.—Macrophthalmia Stage. a. Mouth Funnel (Vestibulum oris), Mouth and Teeth. b. Body Form, Colour and Measurements. Plate (1897) described as a new genus and species of lamprey from Chile, Macrophthalmia chilensis. In a later paper (1902), after another specimen had been obtained, he recognised “Macrophthalmia” as a young stage of his Geotria chilensis. He says further “und ganz einwandfrei ist diese Deutung auch jetzt noch nicht, da nur Alkoholexemplare zur Untersuchung gelangten.” The writer has been able to secure from New Zealand rivers a number of specimens (Fig. 2) which agree with Plate's description (1902) of the above form. Further he has observed the metamorphosis of New Zealand Ammocoetes into these forms, so that there can be no doubt we are dealing with young forms of Geotria. It is proposed to retain in this paper the term “Macrophthalmia,” as Plate (1924) in his Allgemeine Zoologie und Abstammungslehre, part 2, has already done, understanding by it the completely metamorphosed Ammocoetes while still found in fresh water. We may thus speak of a Macrophthalmia stage in the life history of Geotria. Macrophthalmia stages may be obtained in the rivers at the same spots as house the Ammocoetes, and so far as my observations go, only in February, March and April. a. Mouth Funnel (VestibulumOris), Mouth And Teeth. The margin of the mouth funnel (Vestibulum Oris), is circular. (Fig. 3). It carries externally an incomplete circle of cirri, small cone-shaped structures, and internally a complete circle of fringed processes (Blättchen). Two of the cirri, one placed at each side of
the mouth funnel, are prominent, much larger than the others, and may bear the silvery sheen which characterises the lateral and ventral surfaces of the body, or may be coloured as the two dorsal longitudinal coloured bands. They are referred to by Plate (1902) as tentacles. The remaining cirri are small and, when looking directly at the mouth-funnel, are not visible, being hidden by the fringed processes, the two large cirri (tentacles), however, project beyond these fringed processes and hence are visible in this position. Between the two large cirri (tentacles), i.e. dorsally, I count six, seven or eight small cirri. Below each large cirrus, i.e. at the lateral margins of the mouth funnel, I count four or five small cirri. Cirri are present thus at the dorsal and lateral margins of the mouth funnel. The number of cirri in Macrophthalmia, counting the two large ones (tentacles), is about eighteen to twenty and they form an incomplete circle or horseshoe. The fringed processes, on the other hand, form a complete circle, internal to the cirri. The number of these processes (Blättchen) is about sixty. A drawing of a single fringed process is given (Fig 4). The labial teeth line the mouth funnel. They are arranged in arched radiating rows as shown in Fig. 3. They decrease in size from within outwards. Posterior to the infra-oral lamina, however, is only a single row of teeth, large and oblong shaped. The supra-oral lamina carries four cusps—two inner and two outer. The inner are smaller and sharply pointed—the outer are larger with rounded edges. Fig. 3.—Macrophthalmia. Mouth funnel and Mouth. FP, fringed processes; LC, lateral large cirrus; SO, supra-oral laminae; IO, infra-oral lamina. The lingual teeth do not show. Fig. 4.—Macrophthalmia. Fringed process in profile. Fig. 5.—Macrophthalmia. Ant. lingual lamina in profile. Fig. 6.—Macrophthalmia. Ant. and Post. lingual laminae seen from above after dissection. AL, ant. lingual; PL, post. lingual.
The infra-oral lamina has a cuspidate margin. The cusps are small and number twelve in the specimen drawn. The use of the terms “maxillary” and “mandibular” frequently applied to the supra-oral and infra-oral laminae has been avoided in this paper, since according to Sewertzoff (1914, quoted in Bronn 1905–24), the Cyclostomes have arisen “aus einer sehr primitiven Kraniatenform, welche eine verhaltnissmässig grosse Anzahl von Kiemenbogen und Kiemenspalten (mindestens 12 Paare) besass” and again, the mouth opening is “viel weiter rostral als bei den Gnathostomen gelegen…. sie wird hier nicht vom Mandibular-bogen, sondern von Elementen, welche rostral vom dritten Prämandibularbogen liegen, begrenzt.” Further, the mouth proper is bounded above and below by the supra- and infra-oral plates. The great extension forwards of the lip encloses a space before the mouth—this is the mouth funnel or Vestibulum Oris (Bronn 1905–24). The lingual armature consists of an anterior (outer) lamina and a posterior (inner) pair of laminae. There are three cusps on the anterior lamina (Figs. 5 and 6). The middle cusp projects farther than the lateral ones. Nor is the middle cusp in quite the same horizontal plane as the two lateral—it is, in fact, rather nearer the ventral surface than they are. As regards the posterior pair, there is on each side a lamina roughly triangular in surface view. The inner margin of each lamina is cuspidate the cusps directed inwards and backwards when viewed from above. There are four cusps on each lamina. The fold of soft tissue which Plate (1902, Fig. 16) shows in Macrophthalmia is evident in my specimens and may be observed in the living Macrophthalmia when sucking on to the side of a glass vessel. It is evidently very vascular, for it then shows as quite red. It is a transversely placed papillated fold of soft tissue situated below the anterior lingual lamina and above the infra-oral lamina. Between outer and inner lingual laminae is another folded area of soft tissue. In a living Macrophthalmia sucking on to the side of a glass jar all the teeth may be seen—labial, supra-oral and infra-oral, inner and outer lingual as well as the vascular fold between infra-oral and outer lingual laminae. b. Body Form, Colour And Measurements. The nasal aperture is at the summit of a small papilla and the aperture is triangular (Fig. 7), tapering anteriorly and broadest posteriorly. The bright white pineal spot is at the level of the two gaps in the dorsal longitudinal coloured bands. It is placed in the middle of a clear elongate patch of skin, from which pigment is absent. In preserved specimens the pineal spot proper does not show, but the clear elongate patch of skin remains obvious. This is the “Scheitelfleck.” (Fig. 7). Here I must draw attention to a statement in Plate (1924)) “Die Macrophthalmia-Larve von Geotria chilensis besitz nach Untersuchung eines Exemplars überhaupt keine Parietal-organe; dass sie aber früher vorhanden gewesen sind, geht
aus dem Fehlen des Hautpigments zwischen den Augen hervor, wodurch ein heller ovaler Fleck gebildet wird (611A). Darnach ist anzunehmen, dass sie bei der erwachsenen G. chil. auch fehlen.” The explanation of this anomaly is obvious from what has been said above. These organs do not show in preserved specimens. In the living Macrophthalmia, a bright white spot is seen in the centre of the “Sheitelfleck,” representing these organs. Sections show that both organs are present in Macrophthalmia. In the eye the surface of the cornea is gently convex and the iris appears to have a silvery sheen simliar to that of the lateral surface of the body. In the living specimen the pupil appears black, and the transparent lens projects some distance through it and appears almost to touch the cornea. Fig. 7.—Macrophthalmia. Dorsal view of eye-region of body. LCB, longitudinal coloured bands, with gaps above eyes; NP, nasal papilla and aperture; SCH, “Scheitelfleck” with pineal spot proper. At the dorsal margin of the pupil, the edge of the iris is continued into one or two small irregular prominences. Usually two are found but sometimes three. They are projections, actual continuations, of the margin of the iris and project laterally towards the cornea like little shelves. The gill pores are narrow slits—elongate dorso-ventrally, narrow in the antero-posterior direction. They are placed one behind another, in a line directed backwards and obliquely downwards. The cloacal aperture is situated below the anterior end of the second dorsal fin. In form the body is compressed from side to side—and rather deeper in the eye and gill region than anywhere else. Compared with a large Ammocoetes, Macrophthalmia appears considerably thinner.
Two dorsal fins and the caudal fin are present—quite separated from one another (Fig. 2). Fin rays are present in all. This description of the colouring of Macrophthalmia is based on living specimens. Running down the mid-dorsal line is a dark band, which extends to the caudal fin. In this band are placed the nasal papilla, pineal spot proper and “Scheitefleck,” and first and second dorsal fins. On each side of this and still situated dorsally is a longitudinal coloured band, extending also to the caudal region. Each coloured band is interrupted above each eye by a narrow transverse gap, shown in Fig. 7. Anteriorly the two coloured bands converge and meet—the meeting spot being at the anterior tip of the dorsal surface of the animal. Each coloured band is made up usually of three parallel longitudinal streaks—each streak betraying a different colour. But the streaks are irridescent—hence the colour betrayed by the band varies according to the lighting and the angle from which one regards it. A green to green-blue (peacock colour) effect is very common, while purple to mauve effects are also noticeable. The fins—first and second dorsals and caudal are usually tinged with dark, but sometimes a blue-green tinge is noticeable. Running alongside each longitudinal dorsal coloured band and to the outer side of it is a dark area which may vary somewhat in extent. This area may be quite narrow transversely or it may encroach some little way on to the lateral surface. The lateral and ventral surfaces are silvery—the sheen is bright and shining. The ventral surface is quite narrow transversely and is marked off from the lateral surfaces by two distinct lines which thus enclose the ventral surface. These lines commence at the margin of the mouth funnel—are farthest apart below the eyes, so here the ventral surface is widest—are still fairly far apart in the gill region and closer together for the remainder of their course to the caudal fin. The sheen of the ventral surface is not so bright as that of the lateral surfaces. In formalin specimens the two dorsal coloured bands are fainter—and appear of a light blue green. The sheen of the lateral and ventral surfaces is lost. The two lines marking off the ventral surface are still to be seen. Measurements. (Macrophthalmia stage). I. II. III. cms. cms. cms. Length of specimen 10.8 9.8 11.2 Tip Snout to 1st dorsal 6.5 5.6 6.5 " " 2nd " 8.3 7.3 8.4 " " caudal fin 10.1 9.0 10.1 " " cloaca 8.2 7.3 8.3 " " 1st gill pore 1.1 0.8 1.0 " " 7th " " 2.0 1.7 2.0 " " nasal aperture 0.5 0.4 0.5 Length 1st dorsal fin 0.9 0.9 0.9 " 2nd " " 1.3 1.2 1.3 Height 1st " " 0.2 0.1 0.2 " 2nd " " 0.3 0.2 0.3 Distance between two dorsal fins 0.8 0.8 1.0 " " 2nd dorsal and caudal 0.4 0.4 0.5 Diameter of eye 0.2 0.2 0.2 Height of body 0.5 0.4 0.5
5.—Velasia Stage. a. General. b. Mouth-Funnel, Mouth and Teeth. c. Gill-pores, nostril, eyes and fins. d. Lateral-line organs. e. Measurements. a. General. Between the Macrophthalmia stage, when it leaves the river for the sea, and the Velasia stage, when it leaves the sea and starts the ascent of a river, for the purpose of spawning, a gap occurs in our knowledge of the life history of Geotria. This period is passed in the sea and, so far as I know, no observations have been recorded on Geotria in this state. The period must be of some duration, since growth in length takes place from 10 to 11 cms. (Macrophthalmia) to 50 to 60 cms. (Velasia), and growth in thickness from .3 to .4 cms. to 2 cms. approximately. Nutriment is, no doubt, obtained in the “semi-parasitic” manner characteristic of lampreys, i.e., by sucking on to the skin of a fish and by means of the armature of horny teeth rasping a hole in the skin and flesh and sucking the blood and juices. I have myself allowed a lamprey to suck on to my hand, when it immediately drew blood. The sensation resembled that caused by a pin-prick. On removing the lamprey a small wound was seen, consisting of three nearly parallel scratches. The wound was evidently caused by the anterior set of lingual teeth, but if the posterior set was brought into play also, I imagine quite an unpleasant wound could be caused. It is reported that many fishes, especially those attacked at once by several lampreys or those repeatedly attacked, die as a result of their wounds. (Surface, quoted in Bronn 1905–24). Gage (1928), quoting earlier observers, states that sea-lampreys are known to feed on cod, haddock, mackerel, shad, sturgeon, salmon and even the basking shark. He reports that the American lake lamprey attacks pike, pickerel, bullheads, carp and suckers in the lakes. Even bowfin, garpike and sturgeon are said to be attacked. The same observer was able to keep lake lampreys and fresh water fish in a tub and watch the lampreys feeding on the fish.* The reader is referred to the paper quoted for an account of these experiments. According to Gage the food of the lamprey is blood, any minced muscle or other finely divided tissue present in the intestine is to be regarded as accidental “a by-product, so to speak, of the process for getting the blood.” It is considered improbable that lampreys, as often stated, feed on insects and worms. After their “semi-parasitic” life in the sea, the lampreys (Geotria) return to the rivers, which they enter and ascend in shoals or swarms. I have been told by Maoris that hundreds may be caught at one trap in one night and the season during which they run lasts for two or three months, so it appears probable that every year great numbers of lampreys ascend the New Zealand rivers. Yet,
generally speaking, the lamprey is unknown to and unseen by the white man in New Zealand. The reason for this is that the lamprey travels probably only by night, hiding during the day-time. Mr. T. W. Downes of the Whanganui River Trust Board says in a letter to me, “They are seldom seen, personally I have only seen one swimming with a zig-zag motion up-stream—it had a bluish sort of appearance.” Mr. Downes has spent years on the Whanganui River and has had more opportunity of coming across them, if they were to be seen, than anyone else. Further on he says “I think they travel mostly at night, which is probably the reason why they are so seldom seen, but the Maoris tell me that when the water is discoloured by floods, they travel day and night alike.” Mr. W. J. Gray of Okato says in a letter “The lampreys enter the rivers in this locality (Taranaki) about April and make at once for dark secluded places, such as shingle banks, holes under stones and boulders and crevices along the river banks. Such special holes under boulders were highly prized by the ancient Maori and were handed down from generation to generation. They were called ruawhaowhao. The progress of the lamprey upstream depended largely on the rainfall and the condition of the water. When a flood came and caused a stirring of the shingle and mud banks, turned over the stones and generally shook things up in the bed of streams, then away went the lampreys (i.e. upstream) and the darker the night—moonless and overcast they preferred above all—the greater the movement and commotion amongst the lampreys.” How far do the lampreys travel up-stream? This depends on the length of the stream. Thus in the Whanganui River, a river navigable by small river boats for 150 miles up to Taumarunui, I have found Ammocoetes at Taumarunui and, no doubt, they could be found higher up, but I was unable to investigate the higher reaches. Thus in this particular river, it is almost certain the lampreys travel 150 miles and probably more up stream from the mouth. But many of the streams which lampreys ascend, e.g. those around Mt. Egmont in Taranaki and a few in the Wellington District, are comparatively short, say eight to twelve miles in length. Here the lamprey has only a short distance to travel. In the Makara stream near Wellington I have found lampreys far up, perhaps one to two miles from the source, but not higher up than this. As to the streams around Mt. Egmont, bushmen have told me they have seen lampreys high up the stream, when the stream was running through bush. Lampreys enter and start the ascent of the streams in the winter months—at the mouths of the rivers they are caught as early as April and during May, June and July in Taranaki. In the South Island they appear to enter the rivers somewhat later. Can any estimate as to the rate of travel of lampreys be made? It is impossible to make any accurate estimate with the present data at our command. Lampreys are caught at Pipiriki on the Whanganui River during August and September. Pipiriki is 60 miles from the mouth of the Whanganui River. The lateness of arrival at Pipiriki we may regard as due to the distance which the lampreys have to travel up stream before reaching that
place. But from what has been said above by Mr. W. J. Gray, they may remain in hiding under boulders, etc., for some time. It is recognised that the lamprey, on its entrance to and during the early stages, at any rate, of its ascent of the rivers, is in excellent condition. Specimens taken then are strong and active, the flesh is firm and a good deal of fat is present. In this condition it is said to make excellent eating and is highly appreciated by the Maori as well as by the initiated pakeha or white man. It is probable, however, that lampreys do not feed during their ascent of the rivers. The gut I find empty. Its average diameter is about 3 to 4 mm. In some specimens it appears slightly shrunken, in others, however, it still appears normal. I have not been able to obtain any evidence that Geotria does feed in the rivers—the Maoris could give me no instances of it. To prove a negative is proverbially difficult—nevertheless, in this case, I am inclined to think the negative case is probably correct. Cotronei (1927A) reports that Petromyzon marinus and P. fluviatilis in their ascent of the rivers, in preparation for the maturity of the sexual organs, cease to feed, and at sexual maturity atrophy of the intestine takes place. In regard to Geotria, the most striking evidence I can offer in this respect is the possession of a lamprey, still alive, which I caught in the Makara stream on the 9th October, 1927. Since that date he has been kept in a tank of fresh water in the laboratory without anything to eat. He has thus fasted for a year and five months and still appears quite well. This specimen was, however, caught in the upper reaches of the Makara, and already had a throat pouch. It is probable then that Geotria does not feed in the rivers, and that a gradual process of reduction in the gut occurs. This process is hardly noticeable at first in the Velasia. It is very pronounced in the forms nearly sexually mature. In all specimens examined, caught in their ascent of the rivers, the sexual organs were found to be immature. This applies to specimens obtained from the shorter rivers in May, June and July, and also to specimens obtained from Pipiriki at the end of October. So we may say that in the Velasia stage, the sex organs are immature, a fact already noted by Dendy and Olliver (1901). In regard to the colour which the Velasia exhibits, I was fortunate enough to see some live specimens caught at the mouth of the Manawapou River in Taranaki on 13th June, 1926 (Fig. 22). They had been caught during the night preceding the day on which, I saw them, and were still in the river, confined in a basket. I was surprised to see what beautiful and brightly coloured creatures they were—having hitherto seen only preserved specimens. The two dorsal longitudinal coloured bands were bright and conspicuous—they appeared blue-green, while the sides and belly exhibited a silvery sheen. The colouring agrees with that exhibited by the Macrophthalmia stage described above. Thus the dorsal longitudinal coloured bands unite at the anterior end of the dorsal surface of the body and each band shows a transverse gap over the eye as in Macrophthalmia.
Lahille (1915) referring to his Geotria chilensis says “Viene a veces en grandes cantidades en los mercados de Buenos Aires. Personalmente recogí esta especie en el río Santa Cruz, en donde algunos pescadores la designan con el nombre de bandera argentina haciendo alusíon à las fajas longitudinales blancas y verde azuladas que se extienden sobre las regiones laterales y dorsal y que dan al animal, cuanda nada, el aspecto de un gallardete que flamea.” (It comes at times in great quantities in the markets of Buenos Aires. Personally I have collected this species in the river Santa Cruz, where some fishermen call it the Argentine flag, in reference to the longitudinal white and blue-green bands which extend along the lateral and dorsal regions, and which give the animal, when swimming, the aspect of a waving pennant). Evidently, then, the bright colouring which the Macrophthalmia stage shows before its passage to the sea is retained by the lamprey during its “semi-parasitic” life in the sea, and is still visible in those specimens about to start their migration up the rivers to the spawning grounds, when caught near the mouth of the river. But this bright colouration is not retained by the Velasia in the fresh water of the rivers. Specimens caught higher up the rivers have lost the brilliancy of specimens caught at the mouth. In general, the dorsal surface appears of a uniform drab grey, while the sides and belly show lighter. Traces of the coloured bands may persist and be recognisable merely as dark bands on the dorsal surface. In one specimen obtained from Pipiriki at the end of October, 1928, the two bands were still recognisable as dark bands, in other specimens from the same place and obtained at the same time the bands could not be distinguished in the general drab dark grey of the dorsal surface. Smitt (1901) describes a lamprey from the Rio Gallegos, South America, which he provisionally names Geotria macrostoma, forma gallegensis. He says “Ce qui le distingue de toutes les descriptions et de toutes les figures que nous connaissons des autres Geotria, c'est un aplatissement du dos, limité par deux plis cutanés longitudinaux, parallèles en avant mais peu-a-peu convergents en arrière … …” and further, “Dans la těte les plis semblent se continuer en dessus des yeux et sur le haut du museau, divergents en avant; mais comme ľexemplaire a été desséché une fois, ce qui a rendu la peau pleine de rides, la continuité des dits plis, surtout sur la nuque, est difficile à constater.” From what has been said above, I would suggest that these longitudinal skin folds really represent the dorsal longitudinal coloured bands (or their remains) which we have seen to be present in the New Zealand lamprey, particularly in view of the fact that Smitt's specimen had been dried once, so that the skin was full of folds. b. Mouth Funnel, Mouth And Teeth. As in Macrophthalmia, the margin of the mouth funnel carries an incomplete circle of cirri externally and a complete circle of fringed processes internally. (Fig. 8). The number of cirri varies from fifteen to twenty-two, eighteen being a common number. They are arranged in a horse-shoe shape, the gap being ventral. Two of
the laterally placed cirri (tentacles) one on each side, are more deeply pigmented and larger, and hence more striking to the eye than the others. The number of fringed processes is about sixty. A drawing of one is given (Fig. 9.). The labial teeth are arranged in rows radiating outwards (Fig. 8), except ventrally, where is present only a single row of teeth of rectangular shape. The labial teeth are shed at intervals—frequently it is easy to prize off one with a needle, when below is found another formed to take its place. The supra-oral lamina carries four cusps—two broad outer ones and two more sharply-pointed inner ones. (Figs. 8 and 10). Lahille (1915, Fig. 4) figures the supra-oral dentary lamina of his Geotria chilensis. In the attached legend he says “Entre las puntas medianas se ve un tercer par de puntas muy pequeñas, rudimento del par desarrollado en Caragola, género en el cual las dos Fig. 8.—Velasia stage. Mouth funnel and Mouth. × circa 1¼. Externally the incomplete circle of cirri, internally the complete circle of fringed process. SO, supra-oral lamina; IO, infra-oral lamina. The ant. lingual lamina with three cusps shows between it and infra-oral lamina a papillated fold of soft tissue, on each side the pad (Polster) P. Fig. 9.—Velasia. Fringed process in profile. mitades de la placa supraoral son aisladas y trifurcadas.” (Between the middle points is seen a third pair of very small points, rudiments of the like developments in Caragola (Mordacia), a genus in which the two halves of the supra-oral plate are isolated and trifurcated). In my Geotria specimens I have not been able to make out distinctly “a third pair of very small points,” though I have looked carefully for them. The infra-oral lamina has a cuspidate margin. (Figs. 8 and 11). The number of cusps varies from ten to thirteen. Usually I find that the laterally placed cusps are more pronounced than the central ones, and sometimes the indications of centrally placed cusps are very faint. I have not seen regularly a large central cusp, as is figured by Lahille (1915). But there appears to be some variation as to the number and size of these cusps. Both supra-oral and infra-oral horny laminae are shed. The lingual armature consists of an anterior lamina and a pos-
terior pair of laminae. There are three cusps on the anterior lamina, as in Macrophthalmia, and further the middle cusp when well developed is not in the same plane as the other two but in a plane nearer the ventral surface also as in Macrophthalmia. (Figs. 8, 12 and 13). It is not, however, now longer than the other two. During this stage a series of changes takes place, changes which lead to the disappearance of the middle cusp. These changes have been observed and noted by Lahille (1915). With successive sheddings it appears, that the middle cusp becomes smaller and smaller, till finally only a little hillock is left between the two large ones to indicate its position. Figs. 14–16 will illustrate this. Fig. 15A represents the anterior lingual lamina of a Velasia. The horny outer husk or cap was easily prized off with a needle, when below was discovered a replacing structure (Fig. 15B), but with the middle cusp very much reduced and only represented by a hillock. Fig. 14 represents another condition frequently found in the Velasia—the middle cusp as long as the other two but extremely thin and delicate. Fig 16 shows still another condition. Here three little hillocks were noted—it appeared as though with successive sheddings the middle cusp had migrated dorsally or postero-dorsally, so that it is now, though of course much reduced, in the same plane as the other two. It is clear then, that this anterior lingual lamina is shed. Plate (1902) and Lahille (1915) have noted this. Behrend's statement (1892) quoted in Bronn (1905–24) to the effect that the “Gabelzahn” of Geotria is never shed appears therefore to be erroneous. There are two posterior lingual laminae, each roughly triangular. The inner margin of each is cuspidate and there are four cusps on each margin. Replacing laminae with cusps are formed under these. Beween the infra-oral lamina and the anterior lingual lamina is a transverse fold or soft papillated tissue. On each side this is continuous with a pad, “Polster” of Plate. These two pads are situated, one on each side of the pharynx, and at times appear very vascular. Between anterior and posterior lingual laminae is another papillated fold—“blumenkohlartigen Krause” of Plate. In preserved specimens between these two folds, the anterior lingual lamina may be often hidden from view. Behrends (1892) has investigated the structure of the outer lingual lamina in Geotria. He names it the forked tooth. “Die Gestalt des Zahnes ist die einer Gabel mit zwei Zinken deren Spitzen leicht nach der Unterflache der Zunge zu gebogen sind. Zwischen den beiden langen Zacken befindet sich noch eine kleine, schlanke Hornspitze (Figs. 1 and 2 HS), so dass das ganze Gebilde den Eindruck einer Fischgabel macht und ich den obigen Namen dafür wählte.” As I have indicated before, the outer lingual lamina in Geotria does not possess originally the form described above, i.e., two lateral prongs (cusps) with a smaller slender middle prong. The original form, as exhibited in the Macrophthalmia and early Velasia stages, shows three equally developed cusps, the central one not in quite the same transverse plane as the other two. (Figs. 5 and 13). But after the Velasia has entered the rivers, this horny lamina or
cap with three equal cusps is shed and then a replacing lamina below it is revealed, which shows however only two large cusps and a much smaller central one, i.e., it is a “Gabelzahn.” It is probable there may be two or three sheddings before the central cusp reaches its greatest reduction. (Figs. 12, 13, 14, 15A and B, 16). When the central cusp has reached its greatest reduction (Gabelzahn), it appears that no more replacing structures are formed under this outer lingual lamina. Fig 10.—Velasia. Supra-oral lamina. The scale on this figure applies also to Figs. 11–17. Fig. 11.—Infra-oral lamina. Fig. 12.—Ant. lingual lamina from before. Fig. 13.—Ant. lingual in side view. Fig. 14.—Ant. lingual with attenuated central cusp. Fig. 15A.—Ant. lingual. Fig. 15B.—The same after outer horny cap has been removed. Fig. 16.—Another ant. lingual. Fig. 17.—Post lingual laminae. In the specimen (or specimens) which Behrends possessed, the outer lingual lamina was already at the “Gabelzahn” stage. He investigated this structure histologically and found no replacing lamina below. Since, however, he was unaware that at an earlier
stage this lamina possessed three equal cusps and was certainly subject to sheddings then, the conclusions to which he comes, based on examination of only “Gabelzahn” stages, are erroneous. “Dieser Verhornungsprocess, … … geht bei dem Gabelzahne während des ganzen Lebens vor sich, so dass es bei diesen Horngebilden niemals zur Entstehung einer zweiten Verhornungsschicht kommt, wie wir es sonst bei den anderen Zähnen von Geotria und denjenigen von Petromyzon zu finden gewohnt sind.” Here a contrast is drawn between the outer lingual lamina and the other dental laminae of Geotria; and again “Der Gabelzahn wird nie gewechselt. Die Hornsubstanz, welche durch den Gebrauch des Zahnes abgenutzt wird, findet ihren Ersatz durch die dem Zahne anliegende Stachelschicht. Bei den übrigen Zähnen findet der Zahnersatz durch die Einleitung einer zweiten Hornbildung in einer tieferen Epidermisschicht statt.” This contrast does not exist. Replacing laminae are formed under the outer lingual laminae, as they are formed under the other laminae. This I have observed in Macrophthalmia and Velasia stages. But in the history of the outer lingual lamina there comes a time, i.e., the time when the middle cusp has reached its greatest reduction, when no more replacing laminae are formed. This is the “Gabelzahn” and it was from such a stage that Behrends drew his conclusions. The stage in which no more replacing laminae are formed under the outer lingual lamina is the stage approaching sexual maturity, a stage further in which it is highly probable the animal does not feed. The fact that replacing laminae cease to form here in this stage we may regard as part of the process “ďatrofia inerenti alla maturità sessuale.” (Cotronei 1927A). Just behind the margin of the circular lip, the skin of the body is very loose. If an incision be made in the skin, an extensive subdermal space is opened into. This space is largest ventrally just behind the margin of the lip, where later the pouch will appear. But it extends laterally up to the level of the eyes and can be followed posteriorly as far as the first gill pore, growing less capacious as it goes. It is crossed by strands of connective tissue. Dorsally in this region is a similar sub-dermal space, which extends back as far as the nasal aperture. It is crossed by a transversely placed fold of connective tissue. The skin, then, in this region is firmly attached to the underlying tissue along two lines, laterally placed, at about the level of the eyes. The reason for the development of such extensive sub-dermal spaces in this region would appear to be this. When a lamprey is at rest, i.e. not sucking, the sides of the lip are folded in towards the middle line and the skin posterior to the lip does not appear folded or wrinkled, but smooth. When the lamprey sucks on to an object, the lip is expanded to its greatest transverse diameter and pressed hard up against the object, and the skin just behind the lip is seen to be thrown into folds and wrinkles. The development of this sub-dermal space is probably then to be correlated with the habit of sucking on to foreign objects. In other parts of the body the skin is firmly attached to the underlying tissues. In the Velasia stage indications of the commencing pouch may sometimes be observed. In the specimen figured, an
immature female taken at the mouth of the Manawapou River, Taranaki, there was no external indication of a pouch. (Fig. 22). c. Gill-Pores, Nostril, Eyes And Fins. The gill-pores are elongate-oval dorso-ventrally and narrow antero-posteriorly. Their structure is somewhat complex. Attached to the anterior margin of the pore is a thin flap (Fig. 18 Fl.), free at its posterior edge, which partly roofs over a small antechamber, leading into the gill chamber proper. This antechamber appears as a depression in the body wall, partly roofed over by the above-mentioned flap, the unroofed part opening to the exterior. The antechamber leads obliquely forwards and inwards and has two openings, an internal to the gill chamber, and an external to the exterior. The Fig. 18.—Velasia. Gill pore in surface-view. FL, flap; PD, pad with fringed margin; DF and VF, dorsal and ventral flaps; CO, conical structure. Fig. 19.—Velasia. Lateral-line organs of tail-region. Fig. 20.—Lateral-line organs of lateral-gill region. Same scale as Fig. 19. CV, capito-ventral; CD, capito-dorsal. anterior margin of the external aperture is formed by the free edge of the flap, the posterior margin is formed by a thick pad PD, produced posteriorly into a series of small processes. From the posterior margin of the internal aperture two backwardly projecting flaps, DF and VF, a dorsal and a ventral, take their origin. Only a small portion of each appears in the drawing, since both of them in the greater part of their extent underlie the single thin flap. From the bottom of the antechamber, and before the pad, arises a small cone-shaped structure, CO. An arrow is placed within the antechamber. Lahille (1915) figures a gill pore of his Geotria chilensis. In it I note the white pad with a fringed posterior margin, the cone-shaped structure and what probably represents the single flap and the two underlying flaps. The opening of the nostril is triangular in preserved specimens and at the apex of a small papilla, directed obliquely forwards. The “Scheitelfleck” is visible behind this as an elongate oval clear patch of skin. The pineal spot proper is no longer visible shining through
the “Scheitelfleck” as it is in Macrophthalmia. The eyes are well-developed, betraying an average diameter of about 7 mm. The cornea is gently convex outwards in life, while in preserved specimens it appears flattened. The lens projects out through the pupil and in life appears to touch the cornea. The peculiar little projections of the iris which have been described in Macrophthalmia are present here. Each projection is tinged silvery on its dorsal surface, while on its ventral surface it is black. The iris appears silvery flecked with dark. In my formalin specimens the cornea is opaque, but in living specimens it is transparent. I have noticed the eyeball being moved. The second dorsal fin is about twice as high as the first dorsal. The caudal fin, as noted by Lahille (1915), is rhomboid and not rounded in shape. There is a distinct space between the second dorsal and the caudal fin—that is to say, the two are not confluent. The two dorsal fins are separate. (Fig. 22). The urogenital papilla projects very slightly beyond the level of the ventral surface. d. Lateral-Line Organs. The lateral-line organs appear as little warts or papillae just visible to the naked eye and scattered over the surface of the skin. As is well known, in the lampreys they exhibit a primitive condition in this superficial position since in the majority of Fishes the lateral-line organs become sunk either into open furrows in the skin or into closed canals communicating with the surface at intervals. The arrangement of the organs in Geotria appears subject to individual variation and even in the same individual the two sides of the body are not always symmetrical in regard to them. The arrangement as figured is taken from the Velasia stage. In the Fig. 21.—Mouth funnel (oral disc) and Mouth of a pouched specimen. ♂ Externally an incomplete circle of cirri with two larger lateral ones, internally a complete circle of fringed processes. Note enlarged oral disc—compare Fig 8. Both Figs. X circa 1¼. SO, supra-oral lamina; IO, Infra-oral lamina; P, pad or “Polster.” The two teeth of the ant. lingual lamina show—between them and the infra-oral lamina—the transverse papillated fold.
tail region (Fig. 19) on each side only a dorsal row of lateral-line organs is present. In the trunk, two rows, a dorsal and a lateral, are to be seen. In the ventral trunk region, sometimes a few organs may be distinguished, usually I find none. The dorsal and lateral rows may be traced forwards over the gills as far as the nostril. In the region of the gill-pores (Fig. 20) is a branchial row, consisting approximately of a row above and a row below the gill-pores. In the head region on each side we may distinguish a capito-dorsal and a capito-ventral (Plate 1902) row. In the ventral gill-region two ventral rows are present. Each ventral row is continuous with the capito-ventral of its side. The ventral rows end at the level of the last gill-pore. In some preserved specimens it is extremely difficult to make out the lateral-line organs. Plate's conclusion (1902), however, that these organs first appear in age at about a length of 50 cms. must be erroneous, since I have observed them in Macro-phthalmia and further have also observed lateral-line organs in Ammocoetes. A row of organs in Ammocoetes, corresponding in position to the capito-dorsal row in the Velasia may easily be picked up. We see, therefore, that the Macrophthalmia stage is provided with lateral-line organs before it leaves the rivers and we may reasonably conclude that all Velasia stages are provided with lateral-line organs. Fig. 22.—Velasia stage. Immature female from mouth of Manawapou River. The dorsal longitudinal colour band is shown, note gap over eye.x ⅓. It is unfortunate that the term “Drusenporen” for these organs in Geotria has been carried over into Bronn (1905–24, Fig. 120) though it is provided with an exclamation mark. e. Measurements (Velasia stage). I. II. II. cms. cms. cms. Length of specimen 47 51 56 From tip of snout to 1st dorsal 29 31 34.5 " " of " to 2nd " 37 40 44 " " of " to caudal fin 44 47.5 53 " " of " to cloaca 37 40 44 " " of " to 1st gill-pore 5 5.5 5.3 " " of " to 7th " 9.8 10 10.5 " " of " " to nasal aperture 2.8 3.2 3.2 Length 1st dorsal fin 4 4.5 5.3 " 2nd " " 5.5 6 6.5 Height 1st " " 1.1 1.1 0.9 " 2nd " " 1.8 1.9 1.6 Distance between two dorsal fins 3.8 4.5 4.8 " " 2nd dorsal and caudal 1.6 1.7 2.5 Diameter of eye 0.8 0.8 0.8 Height of body 2.5 2.5 2.5 The longest specimen in the Velasia stage which I possess measures 62.5 cms., the shortest 47 cms.
6.—Adult Stage (stage of sexual maturity). a. The Throat-Pouch. b. A well-developed Pouch present only in Male. c. General. d. Mouth Funnel, Mouth and Teeth. e. The Pouch again. f. Does Shortening Occur? a. The Throat-Pouch. The last stage in the life cycle of Geotria is the pouched stage (Fig. 23), so-called because the skin on the ventral surface of the region, between the anterior tip of the animal and the first or second Fig. 23.—Pouched stage. Male, approaching maturity. Makara stream. × circa ⅓. gill pore, is very loose, folded and baggy and there thus appears a loose bag or pouch in this region. One point should be emphasised here—namely, that in life, as I have been able to observe in five living specimens, the pouch is loose, baggy and folded, but not distended, and projects only a very short way below the level of the ventral body wall. When specimens are placed in formalin, however, fluid must pass into the pouch, which becomes swollen and distended and may finally appear blown out like a balloon. Allowance must therefore be made for this in figures which show a distended pouch, as for example in Plate's Fig. 17 (1902) of Geotria australis. This figure is reproduced in Bronn as Fig. 117 (1905–24). Lahille (1915, Plate 22) figures the pouch approximately as I have observed it in life. Compare my Fig. 23. b. A Well-Developed Pouch Present Only In Male. Dendy and Olliver (1901) and Plate (1902) both assume that the pouch is developed in both sexes. I believe this to be incorrect, and that a distinct and well-developed pouch is developed only in the male. Plate (1902), however, describes a female of his Geotria chilensis with a pouch—I quote his words—“Ein Kehlsack fand sich nur bei dem einen Weibehen von 49 cm. (Fig. 7, 8 sac); er war aber nur klein und sprang nicht weit vor, ohne dass ich zu beurtheilen vermöchte, ob dies durch etwaige Contraction der Hautmusculatur veranlasst worden ist.” This pouch, judging from his statement and figures, is quite small and not comparable to the well-developed pouch of the male. I possess two females, which, from the state of the ovary, are nearly sexually mature. They do not show pouches, but only faint indications of a pouch in the form of slight corrugations of the skin and a very weak swelling in this region. In no case— in the literature, in specimens in New Zealand, in my own col-
lection—can I find a female with a well-developed pouch. The specimen of Smitt (1901) Geotria macrostoma f. gallegensis, is a female “sans poche goître,” and later “mais on en trouve un vestige rappelant ce qu'on peut voir chez notre Petromyzon marinus.” It seems probable also that this is an old specimen, i.e. near the end of its life-cycle, from what I can judge and from what Smitt himself appears to suggest: “C'est un plus-ou-moins du développement des cartilages et de la substance cornée du měme type. Si l'on place les espèces décrites dans l'orde suivant: Velasia chilensis, Geotria australis, Exomegas macrostomus, et enfin notre exemplaire, on voit une série continue de développement de ce plus-ou-moins.” Plate (1902) possessed two specimens of Geotria australis: “2 noch nicht ganz geschlechtsreife Männchen, beide mit riesigem Kehlsack.” Lahille (1915) does not indicate the sex of his specimens. The facts which led me to believe that a well-developed pouch appears only in the male were these: 1. an examination of the gonads of all pouched specimens in New Zealand; 2. the finding together at the same time and place of pouched male and pouchless female forms, both nearly sexually mature. 1. Besides examining the gonads of my own pouched specimens, through the co-operation of Museum and University authorities in New Zealand I was able either to examine personally or to have a small portion of the gonad sent to me of all the pouched specimens in the country. The results are tabulated below: Place. No. of Specimens. Sex. Auckland Museum 1 Male Dominion Musuem 2 " Victoria University College 1 " Canterbury Museum 3 " Otago Museum 5 " Cawthron Institute, Nelson 1 " Own Collection 8 " 21 Thus twenty-one pouched specimens, so far as I know, all that are preserved in New Zealand, are male. 2. On the 18th January, 1928, there were brought to the laboratory by some boys, Henry Gestro and his brothers, who had frequently assisted me in searching for lampreys previously, two live lampreys which they had caught in the Makara stream, near Wellington. They had been found in the upper reaches of the stream, under two stones within a couple of yards of each other. One had a large well-developed pouch and large oral disc, was a male and died in four days. I learnt afterwards that this one had been caught by a hook in his mouth and to this I am inclined to attribute his death. The gut was reduced and thread like, the gonad well formed. The testis was sectioned and though fixed some hours after death, all the testicular tissue appeared active in various stages of spermatogenesis, and in the peripheral follicles spermatids or spermatozoa could be seen. This specimen was therefore near sexual maturity. The other specimen had no pouch, a small oral
disc comparable to that of a Velasia stage, and was a female. It was killed after ten days. The gut was reduced and thread like, the ovary immense, the eggs exhibiting an average diameter of about .75 mm. In the pouch region, a very faint swelling was visible. It would not be noticeable unless one looked for it. Both specimens were therefore approaching or near to sexual maturity, and they were found within two yards of each other on the same date. The difference in appearance of the two sexes at this stage, as regards pouch and oral disc, is so striking, that at first sight and without examination of other stages, one might be excused for thinking of two species. On 26th February, 1927, Mr. W. J. Gray of Okato, sent me a pouched lamprey. Though dead one or two days before arrival, the testis was sectioned and examined. Its condition agreed with that of the one described above, except that I could not be sure of seeing spermatids or spermatozoa. The gut was thin and small. Later Mr. Gray informed me that this was one of four, all caught together. Three of these were pouched, the other without a pouch. It seems safe to say, then, that the male, before attaining sexual maturity, develops a large pouch, but there is nothing to suggest that the female ever develops a large pouch. c. General. The following are the dates at which pouched lampreys have been caught: February, 1927 Kie-hi-hi. 9th October, 1927 Makara—still alive in tank. January, 1928 West Coast of South Island. 18th January, 1928 Makara. 12th February, 1928 Wainui-o-Mata. 30th May, 1928 Okato. 25th November, 1928 Makara—two specimens. In all these the testis was large and well-developed, but does not appear quite mature, though obviously approaching sexual maturity. Plate (1902) reports the same of his two pouched specimens “nicht ganz geschlechtsreife Männchen.” Of the two females I possess, which, judging from the size of the eggs cannot be very far from sexual maturity, one came from the River Leith, Otago, South Island, sent to me by Professor Benham on the 10th June, 1927, the other was caught in the Makara stream, on 18th January, 1928. It is not possible, therefore, from these insufficient data, to announce a precise spawning time. It may vary a good deal, particularly in the two islands, and may extend for some considerable time. In all these pouched specimens and in the two nearly ripe females, the gut is very reduced. It is thin and thread like with collapsed lumen. Its diameter is about 1 mm., whereas the gut of the Velasia stage shows a diameter of about 3 to 4 mm. A gradual reduction of the gut therefore takes place with the entry and ascent of the rivers. It is highly probable, as noted before, that Geotria (Velasia and adult stages) does not feed in fresh water.
In this stage of its life history, the lamprey is found in the upper reaches of streams and rivers, under stones. One interesting (and annoying) point is the apparent rarity of the lamprey in this stage. It is extremely difficult to find a pouched lamprey. I have spent many days wading in streams and turning over stones, searching for pouched forms, but have only found myself four. The same thing has been remarked to me by a riverman who is familiar with the lamprey. Most of the Maoris I have met have never seen a pouched lamprey—certainly they do not attempt to catch it, as they do the Velasia stage; and yet the lampreys (Velasia stage) ascend the rivers in swarms. One correspondent in regard to the Mataura Rivers, says: “Fifteen years ago I saw them in millions!” Dendy and Olliver (1901) suggest that according to Maori statements the pouched forms return to the sea. Maoris at the mouth of the Manawapou River have also told me of finding pouched forms about March, returning to the sea. These have been found in eel-traps, since about this time eels migrate to the sea, and traps are set for them by the Maori. It is probable that some, probably the majority, die in the upper reaches of the rivers. A farmer in Okato has told me he now and then finds pouched lampreys floating dead on the surface of streams on his farm. But even if many do return to sea, it is almost certainly only to die. The changes which the lampreys have undergone in the rivers, e.g. the reduction in size of the gut and no doubt the exhaustion of spawning, further the increase in size of the oral disc and the development of the pouch in the male, would seem to negative a new lease of life. No pouched forms are found ascending the rivers with the Velasia stage. According to Gage (1928) the sea and the lake lampreys of New York State all die after spawning and “none of them ever returns to the ocean or the lakes to recuperate and prepare for an additional generation.” Cotronei (1927A) for Petromyzon marinus admits that, after spawning, the lamprey may possibly return to the sea. But if so, it is only to die. “Ma che l'animale non possa riparare alla deficienze di nutrizione e alle atrofie inerenti alla maturità non vuol dire che non possa avere, in qualche caso, la forza di discendere al mare.” The brightness of colour and sheen which characterises the Velasia upon its entrance into the rivers is not retained in fresh water. The two pouched specimens which I caught recently (25th November 1928) in the Makara stream still showed faintly indications of the two longitudinal dorsal bands. In the pouched specimens it is usually impossible to find traces of these bands, the dorsal and dorso-lateral regions are dark brown to gray, the lateral and ventral surfaces rather lighter. The peculiar little shelf-like projections of the iris, already noted in Macrophthalmia and Velasia stages, are still present in this last stage of the life history, both in male and female. The tail now contrasts in depth with the rest of the body, which contrast is not noticeable in the Velasia. Plate's figure (1902, Fig. 17) illustrates this. Compare also Fig. 23.
d. Mouth-Funnel, Mouth AndTeeth. The mouth-funnel (oral disc) and the teeth are worthy of particular notice in the pouched form, i.e. in the male approaching sexual maturity. Extraordinary growth changes have taken place in these since the Velasia stage. The oral disc itself has grown so that its transverse diameter may be twice that of the Velasia. (Figs. 8 and 21). The cirri and the fringed processes are noticeably larger. Two laterally placed cirri (tentacles) still stand out from the others in being more deeply pigmented and larger. The number of cirri varies from 16 to 20. The number of fringed processes is still about 60. As a result of the increase of the oral disc, the labial teeth are now spaced or separated from each other by the growth of the disc between them. They still correspond in number and relative position to the labial teeth of Velasia. The number of labial teeth in the innermost circle is about 27 or 28 in both forms. The labial teeth themselves have also increased in size. Certain of the cartilages of the head have also increased in size, e.g. annular cartilage, anterior and posterior dorsal cartilages. The region from the anterior tip of the animal to the first gillpore has increased in length. Taking the mean of six Velasia stages, the total length is 56 cms., the snout length 5.3 cms., about one-eleventh of the whole. Of six pouched forms, the mean length is 48 cms., the snout length 7 cms., about one-seventh of the whole. The increase in length is mainly in the region before the eyes as may be noted from the wider spacing of the lateral line organs here. An increase in the breadth of this region is noticeable also. The supra-oral lamina is broader and larger. The outer cusp shows a striking increase in breadth, if it be compared with that of a Velasia. (Figs. 8, 10 and 21). Further, it usually bears one or two vertical grooves. This quite striking difference, due to growth changes, was noted by Ogilby (1869) who, however, considered these two forms, Velasia and pouched, as different genera. The cusps are now marked off from the base of the plate by a transverse ridge, faintly noticeable in the Velasia, more pronounced in the pouched form. In the infra-oral lamina, the laterally-placed cusps appear taller and more pronounced than the central ones. In the anterior lingual lamina, the middle cusp may be still present, usually in reduced form, or its position only may be indicated by a small ridge between the other two. The posterior lingual laminae resemble those of the Velasia stage. Both laminae are rather larger. The transverse fold or soft papillated tissue continuous with the two lateral swellings (Polster of Plate, 1902) is present, as also the papillated fold between anterior and posterior lingual laminae. In pouched specimens sucking on to the wall of a glass tank, the vascularity of the soft tissues in the disc and associated structures is often remarkably shown. On the disc itself, the spaces between the labial teeth show red, while the lateral pads (Polster of Plate) show distended with blood and dark red, the transverse fold between
infra-oral and outer lingual laminae, the cauliflower-like lobe between outer and inner lingual laminae and the soft tissue between both inner lingual laminae all appear very vascular. The lateral line organs of the capito-dorsal and capito-ventral rows are much more widely spaced than in the Velasia. Their number is not increased, however, and the same relative arrangement as in the Velasia is noted. This description of the oral disc and teeth is taken from a specimen with large oral disc and pouch. I possess, however, specimens intermediate as regards oral disc and teeth between the Velasia and the above form. Cotronei (1927) has indicated that in Petromyzon marinus the teeth have a real systematic value—“l'accrescimento che si verifica nel Petromyzon marinus non ha nessuna influenza nel far variare i caratteri, sia del denticoli labiali come dei denti cornei piu grossi. Infatti, nessuna variazione apprezzabile si nota nel numero e nella disposizione dei denti cornei nel cavo boccale dell' esemplare di Petromyzon marinus di cm. 29.8 in confronto di quelli che raggiungono dimensioni di 80 centimetri e piu.” As regards Geotria the agreement in number and arrangement of the teeth in Macrophthalmia and Velasia stages has been shown and may be observed from the figures. (Figs. 3 and 8). The first point to note is that with the entrance of the Velasia into fresh water the middle cusp of the anterior lingual lamina with successive sheddings becomes reduced and may finally be lost, hence producing the forked tooth or “Gabelzahn” of Geotria (Figs. 12–16). Secondly, in the pouched form (male) the labial teeth are larger and more widely spaced owing to the growth of the oral disc between them, and a distinct increase in size in the supra-oral lamina, particularly in the outer cusps is noticeable. The remaining laminae—infra-oral, anterior and posterior lingual—have also increased in size. As to the female, I possess only two specimens, which, from the size of the eggs (about .75 mm. diam.) must be approaching or near to maturity. In these, the oral disc and teeth resemble the Velasia stage, but are slightly larger. The cirri and fringed processes are noticeably larger, but it is only when a Velasia is placed alongside one of these two specimens, that a perceptible increase in the oral disc is noted. The increase does not nearly approach that exhibited by the male. In both these specimens, the middle cusp of the anterior lingual lamina is lost. Finally, it appears that in the approach to sexual maturity the female lags behind the male in two processes—namely, the increase in size of the oral disc and teeth and the formation of the pouch. Both processes are evident in these specimens, but only in a very rudimentary stage. I have no evidence to suggest that females ever pass beyond such a stage. e. The Pouch Again. We may now ask why does the male develop such a large oral disc and pouch, when it has reached the upper regions of the river? The pouch and general looseness of the skin in this region are probably to be regarded as consequences of the increase in size of the
oral disc. When the enlarged oral disc is pressed against an object, e.g. the side of a glass tank, the skin behind is much folded and wrinkled, necessarily much more so than in the case of a small oral disc. Why then is the oral disc so enlarged? I can offer only a tentative explanation, one which I clearly recognise as such. It is within the bounds of possibility that the oral disc is so enlarged in the male in order to enable it to suck onto and to move stones in order to build a nest. If this be so, it would suggest that there is a division of labour here between the sexes—the female reserving herself for the much more exhausting process of forming the eggs (as compared with the production of spermatozoa), while the male performs the work of moving stones and forming a nest, his oral disc being enlarged and hence suitable for this work. But I do not even know if a nest of stones is formed—no one knows as yet. In searches in the streams I have not yet found any traces of the spawning process, or nests of stones, nor any Ammocoetes smaller than 12 mm. long. In a letter Mr. L. S. Mackie says “an angler friend tells me he once saw, some years ago, a lamprey carrying a stone about the size of a tennis ball, but it disappeared into deep water and that was the end of it.” An old Maori told me he once saw some lampreys high up the Patea River with a nest of stones, but I was unable to get a clear account of this. Further observation will be necessary before a decisive explanation can be given. I draw attention again to the fact that in life the pouch appears collapsed and with folds in its wall, but not distended as it soon becomes in formalin specimens. The formation of the pouch and the general looseness of the skin in this region may be regarded, I think, as accommodations to the enlarged oral disc. This explanation was suggested to me by observations of living pouched lampreys, 1. at rest (i.e. not sucking), and 2. sucking on to the sides of glass tanks. f. Does Shortening Occur? Cotronei (1927A) has recently shown that, associated with sexual maturity, an actual shortening of the lamprey, in the species studied by him, takes place. He has been able to show this not only by measurements on numbers of immature individuals (where the individuals measured in each case were different), but also by measurements of identical individuals, before and at sexual maturity, which he has kept alive in tanks. The shortening in some cases is very noticeable. In its general life history Petromyzon marinus probably resembles Geotria more than the other two species, fluviatilis and Planeri, studied by him. In P. marinus an individual of 57 cms. diminished to 47.5 cm., a shortening of 9.5 cm.—the distance between the two dorsal fins decreasing from 2.7 cm. to 1 cm. In a second case, a female of 84.5 cm. diminished to 68 cm., a shortening of 16.5 cm.—the distance between the two dorsal fins decreasing from 3.8 cm. to 1.4 cm. He has been able to show the same phenomenon in P. fluviatilis. The shortening is regarded as “dovuto a processi di atrofia inerenti alla maturità sessuale di Petromyzon fluviatilis e marinus.”
In regard to Geotria I am not yet in a position to bring forward such convincing evidence as that of Cotronei. But what evidence there is certainly points towards such a shortening. A table is given below, drawn up from measurements on six Velasia stages, six pouched forms and two nearly ripe females. Velasia. Specimen. Total length (cms.) From ant. tip animal to 1st gill pore. Distance between 1st and 2nd dorsal fins. Distance between 2nd dorsal and tail fin. Distance from ant. end of 2nd dorsal to end body. Length Tail fin (measured dorsally). No. 1 56.4 5.2 4.7 2.5 12.0 3.0 2 55.8 5.3 5.1 3.0 13.0 3.5 3 52.7 5.1 4.6 2.7 12.5 3.4 4 54.5 5.2 5.0 2.5 12.0 3.0 5 54.2 5.0 5.0 5.0 13.0 3.5 6 62.5 6.0 5.5 2.7 13.5 3.6 336.1 31.8 29.9 16.4 76.0 20.0 Mean 56.0 5.3 5.0 2.7 12.7 3.3 Pouched Forms. Specimen. Total length (cms.) From ant. tip animal to 1st gill pore. Distance between 1st and 2nd dorsal fins. Distance between 2nd dorsal and tail fin. Distance from ant. end of 2nd dorsal to end body. Length Tail fin (measured dorsally). No. 1 48 7.7 3.5 1.1 8.5 3.1 2 54 7.0 4.5 1.8 11.0 3.2 3 52.5 8.0 3.6 1.0 9.5 3.5 4 42.5 6.0 2.8 1.3 8.5 3.0 5 46.3 7.0 2.5 1.2 8.7 3.0 6 44.3 6.0 3.4 1.1 10.0 3.7 287.6 41.7 20.3 7.5 56.2 19.5 Mean 48 6.9 3.4 1.2 9.4 3.2 For Two Nearly Mature Females. (No. 2 had been cut up). Specimen. Total length (cms.) From ant. tip animal to 1st gill pore. Distance between 1st and 2nd dorsal fins. Distance between 2nd dorsal and tail fin. Distance from ant. end of 2nd dorsal to end body. Length Tail fin (measured dorsally). No. 1 45.2 5.5 3.5 1.5 8.7 2.8 2 — — 3.5 1.3 9.0 3.0 These figures seem to support the statement that shortening takes place in the male and female (probably) of Geotria, when approaching or near to sexual maturity. From the table the average length of the Velasia is 56 cms., that of the pouched 48 cms. The increase in length of the anterior region (from anterior tip of animal to first gill-pore) in the pouched form is indicated in the
second column. Decreases in the distance between first and second dorsal fins, in the distance between the second dorsal and the caudal fins, and in the post-anal portion of the body as a whole (fifth column) seem obvious. If shortening does occur, as I think it does, then this phenomenon will solve a problem which has puzzled systematists for many years—namely, the differences in total length and in intervals between the fins in the two forms—Velasia and adult. Further it will explain away the arguments, which Lahille (1915) has forcefully summarised, for recognising two species of Geotria, e.g. the spacing of the fins in his chilensis and their approximation in his australis. Again, if one considers my pouched specimen which has fasted for seventeen months (still alive), a shortening appears very probable and what region is more suitable for reduction, while the sex organs are maturing, than the tail? Unfortunately I did not measure this specimen when first caught. We must note, however, in Geotria in the male, the increase in size of the head region and disc; not that this detracts in any way from what has been said above regarding the general shortening. There still remains one argument of Lahille (1915) which calls for note. According to him, in his G. australis (my adult stage) the two dorsal fins are of equal height, in G. chilensis (my Velasia stage), the second is almost twice as high as the first. I agree that in the Velasia stage the second is considerably higher than the first, roughly about twice as high. But in all my adult stages (Lahille's G. australis) which comprise two nearly ripe females, six pouched males and three living forms, I find the second still higher than the first, though the difference in height is not so pronounced as it is in the Velasia stage. It seems to me as if the second dorsal may diminish in height. Literature Cited. Behrends, G., 1892. Ueber Hornzähne. Nova Acta K. Leop. Carol. Akad. Bd. 58. Halle. Bronn, H. G. 1905–1924. Klassen und Ordnungen des Tier-Reichs. Bd. 6. Abteilung 1. Cotronei, G., 1926. II fenomeno d'accorciamento nella maturità sessuale del Petromyzon marinus. Atti. del. Accad. Naz. d. Lincei, Vol. 3, 6th series, Fasc. 1. —— 1927 L'organo insulare di Petromyzon marinus. Pubbl. della staz. Zool. di Napoli, Vol. 8, Fasc. 1. —— 1927A. Ricerche morfo-ecologiche sulla Biologia comparata dei Petromizonti. Parte 1. ibid. Fasc. 3-4. Dendy, A. and Olliver, Margaret, 1901. On the New Zealand Lamprey. Trans. N.Z. Inst., Vol. 34. Dendy, A., 1902. On a pair of ciliated grooves in the Brain of the Ammocoete apparently serving to promote the circulation of the fluid in the brain-cavity. Proc. Roy. Soc. London, Vol. 69. Gage, S. H., 1928. The Lampreys of New York State—Life-History and Economics. A Biological Survey of the Oswego River System, supplemental to 17th annual report, 1927. State of New York—Conservation Department. Gray, J. E., 1851. Description of a new form of Lamprey from Australia, with a synopsis of the family. Proc. Zool. Soc. London.
Günther, A., 1870. Catalogue of the Fishes in the British Museum, London, Vol. 8. Hutton, F. W., 1873. Contributions to the Ichthyology of New Zealand. Trans. N.Z. Inst., Vol. 5. Kner, —, 1869. “Reise der sterreichischen Fregatte Novara um die Erde” ‘Zoologie,’ Bd. 1, Fische, p. 421. Lahille, F., 1915. Apuntes sobre las Lampreas Argentinas. Anales del Museo Nacional de Historia Natural de Buenos Aires, Vol. 26. Macleay, W., 1882. Descriptive Catalogue of Australian Fishes. Part 4. Proc. Linn. Soc. of N.S.W., Vol. 6. Ogilby, J. D., 1896. A Monograph of the Australian Marsipobranchii. Proc. Linn. Soc. of N.S.W., Vol. 21. Phillipps, W. J. and Hodgkinson, E. R., 1922. Further notes on the Edible Fishes of New Zealand. N.Z. Journ. Sci. and Tech., Vol. 5, No. 2. Phillipps, W. J., 1927. A Check-List of the Fishes of New Zealand. Journal of the Pan-Pacific Research Institution, Vol. 2, No. 1. —— 1927A. Bibliography of New Zealand Fishes. Fisheries Bulletin, No. 1, Marine Dept. Plate, L., 1897. Ein neuer Cyclostome mit grossen, normal entwickelten Augen, Macrophthalmia chilensis, n.g., n.sp. Sitzber. Ges. naturf. Fr. Berlin. —— 1901. Ueber Cyclostomen der südlichen Halbkugel. Tagebl. v. Internat. Zool. Conar. No. 8. —— 1902. Studien über Cyclostomen. 1, Systematische Revision der Petro-myzonten der südlichen Halbkugel. Faun Chil. Zool. Jahrb. Suppl. 5. 4 Hft. 2 Bd. —— 1924. Allgemeine Zoologie und Abstammungslehre, Teil 2. Regan, C. T., 1911. A synopsis of the Marsipobranchs of the Order Hyperoartii. Ann. Mag. Nat. Hist., Vol. 7. Sewertzoff, A. N., 1914. Das Visceralskelett der Cyclostomen. Anat. Anz. Bd. 45. Smitt, F. A., 1901. Poissons d'eau douce de la Patagonie. Bih. K. Svensk. Vetensk-Akad. Handl. Bd. 26. Waite, E. R., 1901–03. Note on Fishes from West Australia. Récords Australian Museum, Vol. 4, No. 2. Woodland, W. N. F., 1914. On the supposed Gnathostome ancestry of the Marsipobranchii. Anat. Anz., Vol. 45.
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Transactions and Proceedings of the Royal Society of New Zealand, Volume 60, 1930, Page 167
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16,111On the New Zealand Lamprey, Geotria australis Gray. Part 1.—Biology and Life History. Transactions and Proceedings of the Royal Society of New Zealand, Volume 60, 1930, Page 167
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