THE NATURALIST.

Otago Witness, Issue 2610, 23 March 1904, Page 64

THE NATURALIST.

Flat Fishes and their Nearest Allies.

As is well known, the flat fishes are only ordinary fishes in which one side of the head and body has become modified in such a way as to represent tho upper surface, the eye<3, which in the very young are disposed symmetrically one on each side of tho head, coming together on one eid'a as development pioceeds in a manner unique among veitebrate animalu. Which are the nearest allies of this extraordinary type and in v;hieh group of bony fishes are its probable ancestors to be sought, is a matter which has occupied tho minds of several zoologists. Until lately the flat fishes, or pleuronectids, were- generally regarded as related to the cod tribe, or gadide, and on account of the akenca of spinous fin-iay3 and of the anterior position of the \entral fins, the two familicio wore bugaded undsr the artificial order oi sub-order of- Anacanths. But anyone who will carefully compare the anatomical structure cf the principal members of these two families cannot fail to recognise the absurdity of such a conception, in suppoit of which not even the excuse of external similarity can be adduced. However, \vu etill read in most modern text-books thai flat fishes are modified asymmetrical gadids.

Within tho last 10 years objections to this view have been raised by Mr J. T. Cunningham and by Sir 12. W. L. Holt, the latter author GuggCGtinq that the vertically swimming ancestor of the flat-fish must ha-*e had a de-ep, fliongly-eompresscd body, sin-h as Platax or Zc-us 'John Dory), in which, unlike most fishes, the veuhal region is as deeply coloured as the dorsal. This suggestion has recently reppived attention from both Dr Thilo, of Riga, and xny=elf, and we have independently reached tha .same concius'ion — viz., that the Zeidje, the family of which our weil-kiio>vn John Dory is the type, are the nearest living allies of the flat fishes. For anatomical reasons, which it would be out of place to explain here, we, however, consider it impossible that the latter should have been de-rived from the former, and v*e regard botii families as descendants of a common type to be sought for among the foss'ls. A representative of this type, or, at anyrate ; something very near to it, I believe to have been found in the Upper Eocene genus> Amphistium, which had been rcfeired to the vicinity of the horse-maekerelis. A restoration of this interesting fc&dl fieh has been given by me in tho Annals and Maga-i-ine of Natural Histoiy, October, 1902. Contrary to what is to be c een in the John Dory, 'the spinous part' of the clor c al fin ia much reduced, and fo.rms a continuous series with the soft part, thus foreshadowing the complete- suppi - e«s:on of the spines in the flat fishes. The lecent discovery by Dr J. D. F. Gilehnet in the deep' eoa- off the Cape of Good Hope of the adult of a fish long known from young specimen- 1 ; only, and named Oreosoma atlanticum, brings to light a further connecting for.n between Amphistium and the John Dory, owing to the much-reduced condition of tho spinous part of the doi-sal fin; and this fish may well be regarded as the nearest lining approach to aflat fish. A short description of the specimen appealed in tho Comptes-Rendus of the French. Academy of Sciences, October 5, T. 903.

Affinity between the John Dory and the flat fishe3 is further suggested by the observations made by Mr L. W. Byrne, and published by him in a recent number of the new journal Biometrika. Mr Byrne, having been struck by the asymmetry n the number and arrangement of the dorsal and anal bony plates (at the base of the fins) in the young of the John Dory, has examined the state of things in a large number of specimens between 2|in and siu in length, captured by Plymouth trawlers, and hie study demonstrates the large proportion of specimens with an asymmetrical arrangement of the plate* anj. the apparent tendency to vary, especially in the direction of an asymmetry in which the plates of the right or of the left side predominate.

Little has be-en observed of the habits of the John Dory, but A^hat we 'know tends to Xhow how a fish of similar form may J-#j-e ea=ily been transformed into one restVig on one side of the body, as does a plaice or a turbot. When at re=t the Joiin Do>-y has been seen to lean against some object for support, and. according to MiByrne, it swim-* in a lop-sided fashion, an,l also seems to uee the soft dorsal and anal fins as organs of propulsion. mo\ing them in waves. It would bo interesting to know whether tha John Doiy "slec-pe," as some wrasses do. in view of tho suggestion put forth by Vorrill a few years ago in -the following terms :: — • ''The- common traitog, or blick fieh (Tautoga, oniti=), has the curious habk of resting upon ono side, half buvied among j>iavel or psi-tly ui'der stones, and is often curved in *fcrange positions. It is easy to imagine that the- flounders originated from some svmmetric&l ancestral form that acquired, like tlio toutccj, the habit of resting upon ono side, a*: first only when sleeping, bat afterwards continually, owing to Iho greater pvotcctiou that this habit and irs imitative colouration afforded. Tho one-sidod colotiration and the changes in Uie position of tho eyes, etc , would gradually follow in accordance with well-known laws of evolution." — C 4. A. BcvuLSNGEf., in tho Field.

Animals and Fire. — "Most animals are afraid of fire, and will fly from it in icircr. To others there i- a fascination about a flame, aud they will walk into it even though tortured by the heat. _ A horse in a burning- stable goes irad with fear, bui a dog is as cool in a fire a^ at any time. He keeps his nose down to the floor, where the air is purest, and sets himself calmly to finding his way out. Cats in fires howl pittiou&ly. They hide their fa^es from ihe light and crouch in corners. "When tl'cir rescuer lifts them they are, as a rule, quite docile and eubdued, nevec biting or scratching. Birds seem to be hypnotised by fire, and keep perfectly still ; even the loquacious parrot in a fire has nothing to say. Cows, like iogs, do not show alarm. They are easy to lead forth, and often fiiict their way out themselvps.

Tiio Fashionable Mole. — The most pro nounced vogue m furs this autumn is not for the stately cable or *he elegant ermine, but for tho common mole, whose soft little skin has hitherto been thought good enough nnl ", £si feamekeeuers" coats and sorus-times

for the waistcoats of country «juire a . This humble and erstwhile despised eivatuic has, therefore, Guddenly r-prnng into importance, an importance which, alas! may but piesage its total extinction. The mole is to be found from the north of Scotland to Japan, but, strangely enough, it is not met with in Ireland. The. length of the cieaturo (including a iin tail) is about 6in ; its body is plump and nearly round ; it has very short legs, the front ovxv> being beautifully adapted for digging; eye« co minute as to escape casual observation ; a long, pointed, and extremely strong muzzle, and a numc--ious and efficient set of teeth. It is covered with a olose, soft, and vehety fur, usually of a black or blaekiaii-brown colour, Tvith a greyish tinge in certain lights. Pure white moles (albinos) havo bee-u observed, but they are exceedingly rave. As is well known, the mole makes elaborate subterranean passages and chambers, and is in this respect an accomplished engineer. It is true that, owing to the male-s gieatly outnumbering the females, many sanguinary battles are fought between the former at that season of the year when their fancy ••lightly turns to thoughts of love" ; but, having overcome the rivalry of his competitors, and persuaded, not without difficulty, tho ooy lady of his choice to share hishabitation with him. he acts in a meet exemplary manner, showing a warm affecrion for his wile, and great devotion to his Tamily when it arrives. — Chambers's Journal.