FISHES AND EARTHWORMS.

Press, Volume LVI, Issue 10270, 13 February 1899, Page 5

FISHES AND EARTHWORMS.

A CHAT ABOUT GEOGRAPHICAL DISTRIBUTION. (By Professor Benh.ui, D.Sc, M A.) The question has not unfroqtieutly been put to mc, since my arrival in the colony, whether I lind anything interesting or novel about the plants and animals of New Zealand. This is a very pertinent question, although to a naturalist it may seem rather superfluous, for by every biologist Xow Zealand is recognised as one of the most interesting laud surfaces of the globe from the point of view of its fauna and flora. It is only necessary for a newcomer k> direct his attention to the fishmongers' shops to be at once confronted with an entirely new set of edible fishes. Indeed, this department of domestic economy is more strikingly novel than any j other to a housekeeper newly arrived from Home. In place of the once familiar mackerel, sprat, herring, plaice, sole, and flounder, halibut, brill, turbot, cod, haddock, and whiting, he now meets with strange and uncouth forms (and names), like the groper, barracoota, moki, butterflsh, garfish, red cod, blue cod, as well as ling» flounder, and perhaps trumpeter and snapper, king fish and frost fish iv their proper seasons. The zoologist, on comparing the two series, finds, indeed, that not one single edible fish which occurs in the northern hemisphere is to be found here in the southern —except, it may be, as a rarcyisifcor, like the John Dory, which quaint-named fish has a very wide range. But, it may be said, we in New Zealand have "cod" and "herring," "flounder" and "sole," "mullet" and "ling," as at Home. This is quite true, of course; the same names are applied to fish here which are entirely different from we may regard as the godparents in the Old Country; as anyone would recognise if they saw the two "herrings" side by side. And this difference is still more evident if, instead of using the popular names, wo used the scientific names. It would, however, be pedantic, let alone uninteresting to the reader, to give a list of the correct names, for the general public has a strong antipathy to science if it is dressed in too many "hard words. But perhaps I may be pardoned if I use in illustration of my point just one or two technical terms. In biology it is absolutely necessary to have some definite language ..which may be understood by our colleagues in France, Germany, Russia, or elsewhere, who, perhaps, would no more know what we Anglo-Saxons moan by a "cod" than would an Englishman at Home realise what is connoted here by "moki" (unless, indeed, he imagined it to have reference to the costermonger's useful servant). We biologists can't help it; we have to nee "hard-words" now- and again. The codfish of the northern hemisphere, the source of that useful, uut generally- Unpalatable, oil, so frequently swallowed in childhood) is knownlo zoologists throughout the civilised world as Gadus morrhua; it is a representative of a larggufamily of marina fishes, many of which are edible. This family, Gadidse, includes the hake, haddock, ling, whiting, and others of the Old Country. Now we-have in New Zealand a "red cod" and a "blue cod" of different merits and of different families. The red cod (sometimes termed haddock) belongs to the same family as the true cod, but to a different genus; it goes by the name of Pseudophycis bacchus. The blue cod (or rodk cod), on the other hand, is not a "cod" at all. It has absolutely no affinity to them; it belongs to a family that includes certain fish known at home as "weevers," which are remarkable for possessing a spine on the gill-cover, which may give a troublesome, poisonous wound, and this family does not yield edible ~-~ in the )'d Country. ■ ' Take, again, the herring —a ' fieh tint a "new chum" misses immensely— a fish that has various merits, whether it be "fresh herring" or a "kipper," or the "bloater" of Yarmouth, or the red herring. This hdfoely and useful Herring is, in zoological parlance, Clupea'harengus; and is the representative of a family to which many other good fishes belong. The New Zealand, "herring," or. more correctly sea-mullet, dees not belong to this family, but.is as far removed from it in the zoologist's system of classification as it is in the ideas of a gastronomist. It, with its fellow, the grey mullet of the -North Island, belongs to the Mugilidae, a family, which is near to the blue cod and the mackerel. One further example may suffice. The native "salmon" of New Zealand, and the true British salmon, are at opposite ends of the series of families of fishes recognised by zoologists. The former is really a "sea. perch" and closely allied to the groper. As to the "flounder," "sole, and other flat fish, they are very much, alike in both countries, and though, genera, belong to the sarite family, the Pleuronectidffi. ' By comparing the whole series of the commoner edible fishes of the two countries, .we findj in short, that in the Old Country the bulk of them belong to three families—the cods or Gadidte, witto eight kinds of species; . the herrings or Clupeidae, with five species; the flat fishes, or rleuronecticUe, with six species. In New Zealand we have of the Godidce only one common specie* (and a second rarer one); of the Clupeidie, , only the pilchard and a much rarer true hewing; and of the Pleuronectidee, only three species. I The bulk of our New Zealand edible fishes 1 belong to quite other families, which provide no representatives in the English fish markets. ' A further inspection of a fiahmqnger't shop id New Zealand, leads us to wonder at the lack of "shell-fish." We mitt the lobster and the crab, the prawns and shrimps. And where are the whelks, the winkles, cockles, and mussels, so much favoured by the poorer classes in our great English towns? They are oot present in New Zealand. In place of the lobster of the. North Atlantic (Hontarus) we have these» crayfish (Palinuruß) in this southern ocean— a very inferior article, by the way. (A different, species of Palinurua sometimes cornea into the English fish markets). And as. .far as my experience goes, we get no other edible Crustacea in chops. , Our marine fauna does, nevertheless, . include prawns and shrimps of a toHj but either . they we not jpimwnt ?|» tht jgtiaU

or do not occur irt sufficient abundance to make it worth while for the fishermen to •end thorn to market. We have, however, the oyster, and we may congratulate ourselves on its plentifulness and cheapness: and, curiously enough, specialists tell us that it only differs from the "Colchester native" in having its shell tinged with purple. The so-called "cockle" (Chione), tho "pipi" of the Maoris, is different from tho cockle of Great Britain. J So much for tho fishmonger's shop. I have referred to it in order to illustrate the vast difference between the animals of the Ola Country and those of New Zealand ; a cMferenee\vhich is payable U> anyoue who has bought or eaten fish in both countries. What is true of our tish is true of other animals and plant*, and yet each animal in the Old Country seems lo be represented here by some animal, not unlike it in liabifc and structure. Kvory place in nature is tilled, though by *»mc different, allied form of life This is «\ self-evident a fact, and one almost to be expected, that it may apj-ear n waste of time to niMition it. and m the old days, during tho iirst half <if tnw century, the differences would have rcc|iiired no explanation: and the resemblances where they exist would have been paW by without a remark. It would all liave been taken for wanted— "they were created here, and that was an end of the .nutter. But. nowadays, we are not so eaml v contented. We are not to bo put oif with "the word "created. We want "to find out why there is so much difference between the fish of this mi. and of that, or between tne animals and birds of ono country and another. it is periectly evident in the letter case that this dii;trei:< t: of fauna Ls not dim u> any incompatibility <:i temj>eramciit i:i the animals. «,r I" any unsuitability of climate, <<r mMiflinency of food, or*to anything of this liind. We know well enough, and oiteu to our sorrow, that when anim.ils foreign to the soil <io roach Nt" v Zealand us a result of nnn's importation, tln-v thrive even betlvr than they did at home." We have only to think of rabbit*, sparrows, thrushes, l'em'ts, sheep, deer, trout, humble-bees, and many plants. There must be something beyond "unsiiitability" <•' environment t> explain I heir absence" here. And this whole matte:- terms itivj great department of. biology, nv.-\ forms a fa-sfinating accompaniment to the other branche. 1 ) r.i the science. This is "geographical distribution." What does "geographical distribution" teach us:".' This is a wide question, but, briefly, by studying and comparing all the facks about the present fauna (or flora) of various parts of the world; by paying duo attention to the geological records of the past inhabitants; by a knowledge of the geological formation of these regions, and of the depths of tli3 intervening oceans, we may reconstruct the maps of the world so as to exhibit the arrangement of land .and sea. in bygone geological ages. In doing this we shall find that islands or continents now separated by wide tracts of ocean were at one time in continuity; that vast tracts of land now continuous and inhabited were at some earlier epoch submerged beneath tho sea, and that a present continent was a series of islands, or had different land connections to those existing now. For this subject, the distribution of marine animals is perhaps less instructive than that of terrestrial or fluviatile Torms. But one interesting fact may be mentioned, viz., that different as our fishes are from those of tho northern hemisphere, yet there is a greater resemblance between them than between the fish of either region and those of the intervening tropical seas. An explana-. tion of this fact would take too much space here. The wide range over which some marine animals may wander is at first sight little surprising, in view of the continuity of the medium in which they live. In reality, however, there are efficient barriers to universal distribution of most forms, in tfoe presence of great depths, or currents of unsuitable temperature, or absence of food, and so forth. It is not surprising, however, that land anhnala are confined to definite islands or continents; and it is rather the faot-tbat similar animals occur in widely separated land areas that renders the subject of "distribution" interesting. Amongst our New Zealand fauna we have many animals which are restricted to these islands,, such as the kiwi, kea, tuatara, and moa, and others. It is not, then, of these that I need write. Nor do I intend to deal with birds at all, seeing that these have frequently been discussed, but wish rather to direct attention to the importance of studying the lower forms, such, as the moUusca and Crustacea, and especially the still humbler earth worms and planarian worms —*hoso shy, light shunning, soft bodied creatures, which have been included amongst the "cryptozoio fauna" by Dr. Dandy. These lowly worms constitute a most valuable element in any discussion on distribution, for tberr soft bodies are extremely sensitive to hygroscopic changes in the atmosphere. It is only during recent years that any attempt has been made to bring them into the discussion on distribution, for the simple reason that they have Deen.but little collected or studied till within the last ten or fifteen years. The cause of this neglect is not far'to seek, for their underground life and the absence of aesfchestic beauty in earth worms fail to attract the amateur, and it is to the amateur that our knowledge of species in any given country is at first due. , In zoology and botany history proves to us that it has usually been toe medical man or the clergyman who has occupied his spare time in ttus useful business of accumulation. Even nowadays, wh<& "professional" biologists are turned out by the Universities, it is ■till the amateur, i.e., the man who doesn't have to make an income by means of his biological knowledge—that builds up our foundations for a systematic treatment of certain groups. This is notably the case in New , Zealand, where we owe much to the enthusiasm of amateurs in various groups of the animal kingdom. The shells of molusca have always been favourites with collectors of all kinds. Their beauty of form and Jolour; the ease with which they can be stored; and the fact that in most cases the discrimination of species and genera can ba effected by merely "a careful examination of the outside, all tend to make the group a popular one. Insects and Crustacea, too, have had their-votaries, notwithstanding the requirement of a certain degree of careful manipulation and minute dissection in the attempt at identification. But the softbodied worms have received little or no attention from amateurs, and even the number of professed zoologists who have specialised on the Planarians and the Earthworms at" the present day, number a mere dozen or so throughout the whole world. Nevertheless, as I have remarked, these worms afford most valuable evidence in the matter under discussion. In this article I wish to illustrate the general scope of geographical distribution by reference to the earthworms of New Zealand, which are very different from those of Australia on the one hand, and Europe on the other. Earthworms, even if anyone takes the trouble to look for them and at them, seem very much alike all the world over, simply because their burrowing mode of life necessitates a soft and more or less cylindrical body. Yet, despite this absence of "variation in shape, a zoologist is able, at the merest glance, to distinguish the earthworms of New Zealand from those of Great Britain. But here, we must give a word of warning to anyone who, being wrought up by enthusiasm, may go out to catch the early worm, that tho earthworms of the Old Country have followed us hither. In gardens and fields, and elsewhere in the neighbourhood of towns, they are very abundant, and seem to have ousted tho native inhabitant. To study the aboriginal tho enthusiast must go to tho bush, or at least to more or less unoccupied areas, whither the universal British worm has «ot made its way • I * lu * l neoess «T here to point out how these rivals differ from one another. Suffice it to state that the European earthworms belon-'s to a family Lumbricidse, Of the twenty species of indigenous earth worms of New Zeaknd sixteen belong to the.family Acanthodnhdae: oi these sixteen eight are species of tho genus Aconthodrilus. the rest belong-to Sener.i which are peculiar to NewZadand. But other epecieV of AcaninoOfUus occur in more or lees distant parts ot-ue world: there are three species in the ZLi Austrau a: another species in the central region of that continent : a different k ipscies in each of the islands of New CaleMicqueries, Kergaekn, Marion , and,,

the Falkland-, and still other species in Chili and Patagonia, and the Cape of Good Hope It may be as well to mention that other genera of the family occur in Africa and in North America, but here we are concerned only Avitii the genus Acanthodrilus, and the problem to be solved by a consideration of their present distribution is, how did the genus spread itself over such a vast distance? The usual means of dispersal of terrestrial auimals from one part of the globe to another—before the traffic by man came to interfere Avith or to aid Nature —depend, naturally, on the character of the animal. Some, "like birds, bats, and insects, can fly through the air; others (besides fish) may swim across lakes, or even narrow arms of the sea; others may possibly be transported on floating trees or logs, or by icebergs. Some bivalves attach themselves to Avater insects; others are stated (on very insufficient evidence) to be carried embedded in mud on tlie feet of birds ; Avhirhvinds may even distribute eggs of small animals, and so forth. But these methods cannot apply to earth Avorrns; their soft bodies render them very susceptible to dryness or to heat. They will not survive any prolonged immersion in salt Avater, so that iioatin.; lugs and trees will not aA*ail for the purpose ; their cocoons, buried in the earth, are not likely to be attached to birds' feet. In fact, the only mode of transport of earth worms—before man's interference—is by direct land communication between the countries concerned. Consequently the various parts of the world in Avhii-li the Acanthndrild_e are found must have been at some time or another connected by land, Avhere there i3 at present sea. Once upon a time NeAv Zealand Avas a much niDio extensive land area than at pro-cut: it stretched westwards as far as Lor I Howe Island : northwards to Norfolk Isi.md and the Kermadecs : soutiiAvards to thii Campbell and Macquarie Islands. For some short period, too, it must have sent out an extension to the north-Avest, to connect with the eastern coast of Australia, no doubt by Avav of NeAv Caledonia. The evidence in favour of these statements is derived partly from the soundings around tho present islands, partly from a consideration of the facts of "distribution." It was, no doubt, by this N.W. extension that the .sjwt.e- of Acanthodrilus passed from New Zealand into Queensland: and at the same time Peripatus and other forms parsed from Australia hither. r But. at some other period, preater New Zetland must have been indirectly connected Avith the southern portion of South America: not only does the distribution of carthAvorms demand this, bufc-ihe presence of similar fresh water fish in New Zealand, lasmama, and Patagonia can only be explained, Irishism though it may seem, v- a land connection This connection was probably by means of a circumpolar Antarctic continent Other facts seem to point also, to a trans-Pacific connection at some epoch. Our earthworms require sompl kind of land connection with the Cape of Good Hope, for there we find an isolated species of Acanthodrilu_— hence some northward extension of the Antarctic continent probably, for we have less evidence on this point, joined Avith the Cape. This great continent when it sank left some traces-the Kerguelen and Marion Islends- in tho Indian Ocean: for the only earthworms that have been collected there belong to this same genus Acanthodrilus, and it is impossible' to conceive how the worms reached these islands but by land bimilar lessons are to be learnt from other terrestrial, soft-bodied worms, like Land 1 lunarians, Land Nemerti_.es,- as well as Crustacea and mollusca. All these terrestrial -_^___r^ - -^-*-"