492 



PISH. 



we observe in the system of nature, of the different 

 races of animals on one another. The season at which 

 fish deposit their eggs varies according to the species, 

 and even the habits of the individual. U is well-known 

 that among salmon, even in the same river, a differ- 

 ence of some months is observable, and we believe 

 that the same remark is applicable to all other kinds 

 of fish. In general, before spawning, fish forsake the 

 deep water, and approach the shore, that the roe 

 being placed in shallow water the influence of the 

 solar rays may vivify it. At that season some fish 

 forsake the salt water and ascend rivers ; and, after 

 spawning, retreat again to the ocean. The eggs of 

 various species of fish belonging to the oviparous 

 order, with distinct sexes, are used as articles of food. 

 Where circumstances permit, they are consumed 

 while in a recent state. In other situations they are 

 salted, and form the well-known article of trade called 

 caviar. The characters which the organs of reproduc- 

 tion furnish in the discrimination of species have been 

 hitherto too much neglected. Connected as they are 

 with the existence of the animal, and exercising a pow- 

 erful controul over its habits, they ought to be examined 

 with care, and their appearances recorded in detail. 

 In the case of those fishes which are ovoviviparous, 

 and range over the wide seas, not requiring to come to 

 the shallow water for the purpose of depositing their 

 eggs, this might be a matter of considerable difficulty, 

 but much more might be recorded than has been done 

 in the case of the spawning fishes ; and they are not 

 only the most numerous, but, in an economical point 

 of view, by far the most valuable of the whole. We 

 must, however, pay some little attention to another 

 branch of the general subject. 



DISTRIBUTION AND MIGRATION OF FISHES. These 

 are subjects which cannot well be separated from each 

 other by any analogies of the facts which we are 

 capable of forming ; and the observed facts are so few, 

 and the connexion of them is so broken, that this is 

 a portion of the subject upon which it behoves us to 

 express ourselves with the greatest diffidence. 



In order fully to see the causes of the distribution 

 of fishes over the wide expanse of the sea in breadth, 

 and through the depths of its waters in profundity, 

 there are many elements required on which our infor- 

 mation is very limited. We know that in the tropical 

 waters the elements of life reach to a greater depth 

 below the surface than they do in higher latitudes ; 

 and if there be any portion round either pole or 

 poles, which is never clear of ice, we may presume 

 that the number of fishes there is comparatively limited 

 both in species and in individuals. Indeed, from all 

 that we know of the matter, we may suppose that there 

 is in the wide ocean of every latitude a depth beyond 

 which no creature can live ; and that, consequently, 

 before such profound depths are reached, there must 

 cease to be any fishes. But what this particular depth 

 may be for any one latitude we have no certain means 

 of ascertaining; because it must depend upon several 

 circumstances, such as the solar action, in respect of 

 latitude, the set of any current which may happen to 

 pass over it, and the character of the bottom ; not 

 merely as respects the soil, or other substance of 

 which it is composed, but as respects the action which 

 may be going on under it. Thus, for instance, if a 

 sea is in the vicinity of volcanoes, and especially if it 

 is studded with volcanic islands, and subject to the 

 production of new ones, there is no doubt that the 

 water must be warmer, and also more subject to be put 

 in motion in such a sea, than in one below which no 



such sources of heat are in operation. Thus, for in. 

 stance, there is no doubt that the Mediterranean, 

 toward Sicily and the shores of Naples, is in some 

 respects analogous to a seething pot ; and the same 

 may be said of the volcanic portion of the Red Sea ; 

 of the sea around some of the Atlantic islands ; aiwJ, 

 in short, of that around every land where there is vol- 

 canic action in the neighbourhood of the sea. If we 

 could go minutely into this subject, which, however, 

 is impossible from the want of the requisite data, we 

 should find that the progressive history of fishes, and 

 the progressive history of volcanic action, have a very 

 close connection with each other. In former times, 

 when the waters of the Mediterranean covered what 

 are now the plains of Languedoc, and many of the 

 summits of the central mountains of France were 

 blazing with volcanic fires, a temperature equal to 

 that at present under the equator may have been 

 given to the waters of the Mediterranean ; and this 

 may have been the reason why, in the accumulations 

 of fossil fishes, which are so remarkably plentiful iu 

 some parts of Italy, there are many species of which 

 there are no types except in the tropical seas ; and 

 those shells and other productions of the waters, which 

 are found in the Mediterranean, of more tropical cha- 

 racter than anywhere else, under the same parallel of 

 latitude, may perhaps be received as evidences of the 

 same fact. We mention these few particulars, not 

 with any intention of entering upon the investigation 

 of a subject of such difficulty and uncertainty ; but 

 merely for the purpose of showing that if the history 

 of the finny tribes could be properly worked out, it 

 would throw much more light upon many of the most 

 interesting points in geology than we at first would 

 be apt to suppose. 



In considering the distribution of fish, the first 

 distinction, and the most obvious one which we are 

 required to make, is that of fresh water and salt 

 water fishes. That there is any permanent structural 

 adaptation to any of these kinds of water rather than 

 the other is rendered doubtful by the fact of some 

 fishes living by turns in the one and in the other, and 

 apparently keeping their health equally well in both. 

 We cannot adduce a more striking or more interest- 

 ing instance of this than that of the salmon, with 

 which every one is so familiar in our own country. 

 Yet even in the salmon, the transition from the one 

 kind of water to the other must not be immediate, 

 otherwise the fish cannot live ; for a salmon which 

 has been habituated to fresh water, will die of suffo- 

 cation if instantly put in sea water ; and a sea salmon 

 will do the same if instantly put in fresh water. 

 When, however, the transition is made gradually 

 enough, the fish not only sustains no injury, but it 

 appears, and is indeed, evidently part of the economy 

 of its nature to make this transition. Not only this, 

 but we believe, in some instances, fishes which are 

 never naturally found in fresh water, but always in 

 the sea, and that at considerable depths, have been 

 brought to live in water scarcely, if at all, impregnated 

 with salt. 



The next distinction of fishes, with regard to 

 locality, is into littoral and pelagic, or those which 

 frequent the shores and shallows only, and those 

 which are discursive through the broad waters. The 

 most remarkable distinction between these is, that 

 the fishes of the shores and banks, like the mammalia 

 of the savannahs or meadows upon land, are generally 

 gregarious or found in jextensive shoals, while the 

 others have much less propensity to congregate in. 



