FLAT-FISH. 



499 



Their manners are, however, worthy of some atten- 

 tion. If we could take a type for sea animals from 

 the animals of the land, \ve might be inclined to say, 

 leaving difference of food out of the question, that 

 these flat-fishes hold nearly the same place in the 

 waters of the ocean that the ruminant mammalia do 

 on the land. It is true that none of them feed on 

 the vegetable productions of the sea, for the fishes 

 which do so have the body placed with its breadth in 

 a different direction, and they are all fishes inhabiting 

 near the surface, and, generally speaking, found only 

 in the warm latitudes. But still the flat-fishes inhabit 

 what may be considered as the fattest pastures in the 

 sea namely, those bottoms of mud and ooze within 

 a moderate range of depth, and also at similar depths 

 where the bottom is soil sand ; but in general they 

 are not found in stony places or among rocks, and it 

 is probable that there are none of them in situations 

 where the bottom is at any very great depth. It is 

 of course not possible to state in general terms the 

 distance from the shore at which the favourite 

 abodes of those fishes either begin or end, because 

 the difference of depth, and the character of the 

 water off shore vary so much, even within a limited 

 extent of coast, that each place must be determined 

 by actual observation. In general, however, they 

 have their chief resorts in those places where currents 

 meet and deposit banks, or where the current of a 

 river and the water of the sea act and react upon 

 each other at the bottom in the course of the tides. 

 Some of them, as will be more particularly explained 

 when we notice the species, are much more landward 

 than others, and found not only in the shallow parts 

 of the sea near the shores, but in some of the species 

 in the rivers and lakes of fresh waters. This is the 

 case with the flounder branch of the family. The 

 soles, which are perhaps among the least discursive 

 of any, are generally found in currents, and in the 

 estuaries of rivers, from about ten to twenty miles 

 distant from the land, according to the nature of the 

 ground ; but when the shores are very steep and 

 rocky, and have deep water at their bases, no such 

 fish are found, and it is probable that the accumu- 

 lation which is found at the bottom of such places 

 consists of matters which are not only dead, but in 

 such a state of decomposition as to be reduced to 

 their merely saline and earthy ingredients, and there- 

 fore unfit for being the food of any animal. 



In those haunts which are congenial to them, the 

 flat-fishes are understood to keep very near the 

 bottom, and to have part of their bodies buried in 

 the soft sand or ooze, with only the head exposed. 

 Their form is remarkably well adapted to this habit, 

 and it is a form which differs greatly from that ot 

 any other vertebrated animal. 



In respect of the general action of their bodies, the 

 flat-fish still preserve the typical form of a fish, that 

 is, thu action of the spine is lateral with regard to the 

 true mesial plane of the great mass of the body, and 

 different from all the land vertebrated animals which 

 have the principal action of their spine vertical as 

 respects this plane. In the flat-fish, however, the plane 

 of the body is turned, so that instead of swimming 

 with the back uppermost and the belly undermost, as 

 is the case with other fishes, they swim upon the side, 

 and with both edges of the mesial plane equally pro- 

 duced through the greater part of their length, and 

 bnly with the cavity of the body, which is generally 

 very short in the extended part, turned a little to 



one side, and the top of the head turned a little 

 to the other. From this form the whole fish is enabled 

 to swim as one continuous flattened body, while the 

 eyes, which are generally very small and close toge- 

 ther, are on the upper surface, the mouth being placed 

 more or less obliquely to one side or other of the 

 snout, and the fins, which answer to the extremities 

 of quadrupeds and birds, placed on the upper and 

 under sides, though also a little obliquely. Generally 

 speaking, the kind of colour and also texture of skin 

 which characterises the whole back of any other fish, 

 is confined to the side of the flat-fish in which the 

 eyes are situated, and the other side, which is never 

 turned up in swimming, is always white. There are 

 some species, however, in which both sides are 

 covered nearly in the same manner, but there is none 

 in which both eyes are not on the same side of the 

 head, as estimated from the position in which the 

 fish swims. 



If the skin is removed, it is found that, though the 

 upper and under sides are not quite the same in their 

 muscular texture, or in their quantity of muscular 

 substance, yet that they have a very near resemblance 

 to each other in the arrangement of their fibres. 

 The principal action of the body consists in bending 

 the spine downwards, that is in giving it a concavity 

 at the middle of the under side, and in some of the 

 species this motion appears to be so differently com- 

 municated to different parts, that there are several 

 contrary flexures of the spine at the same time. It 

 does not appear that the spine of these fishes is 

 capable of much motion laterally, or that the last is 

 with them the chief organ of progressive motion, as if. 

 is in other fishes. The tail can only strike the water 

 upward or downward, and therefore is effective more 

 as a means of ascent and descent than of forward 

 motion. 



It is with the side or lateral fins, answering to the 

 dorsal and anal fins of an ordinary fish, that the pro- 

 gressive motions of flat-fishes are effected. These 

 fins, no doubt, strike the water upward or downward, 

 and not laterally ; but then the bendings which are 

 produced in the body, and in the extremities of those 

 fins, produce a progressive motion, though it is 

 slower, and performed with much more labour in 

 proportion to the effect than in other fishes ; because, 

 while the bodies of these fishes are curved vertically 

 in swimming, the different parts of them are subjected 

 to different pressures of the water, and a portion of 

 the action is taken off by the resistance of the other 

 part of the bend. The pectoral fins are rather small 

 in most of the species, but the dorsal and anal are 

 continued throughout nearly the whole lines of the 

 sides, or rather of the ridge of the back and under 

 part of the body, for these are the true situations of 

 the swimming fins of the flat-fish. When the fish is 

 laid down with its eyes upward, its natural position 

 in the water, that fin which is on the same side with 

 the eyes is to be considered as the dorsal fin ; and 

 the one on the opposite side, where the mouth, the 

 gill-openings, and the vent are met with, is to be 

 considered as the anal fin. In most of the spe- 

 cies the pectorals are situated just in the rear of 

 the upper angle of the gill-openings, and the ven- 

 tral fins in advance of these, near the commence- 

 ment of the anal fin, and partially twisted a little 

 from the side in which the eyes are. These four 

 fins are, however, as we have said, very small in 

 size, and they cannot be very efficient in any motion 

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