77 



For such reasons as these I am induced to conclude, with Dr. Priestley and 

 the ancients, that the air-bladder in fishes is designed for other purposes than 

 merely ascending, or descending, through the water. 



The discovery of what these may be is stUl to be made. 



NOTE. 



P. 65. — " However closely outward forms may approximate, there is no instance, 

 as far as I am aioare, of a coincidence of formation in the osteology of different 

 species of the savie genus." 



When this paper was read at a Meeting of the Naturalists' Field Clubs of 

 Herefordshire, Worcestershire, and Gloucestershire, the above position was 

 denied ; and the felidae adduced in opposition to the text. I consider, however, 

 that we can scarcely be justified in illustrating one g^eat division of animate nature 

 by another. The laws which govern the one may be totally different from those 

 which influence the other. This must apply with the greatest force, when two 

 classes of animals, so far removed in the scale of creation as fishes and terrestrial 

 mammalia, are compared. I was speaking of Ichthyology, alone. Nevertheless, 

 I think it will be found to apply, as a general rule, to every grade of animal life— 

 the felidae not excepted. The numerous species of the genus felis very closely 

 approximate in their osteology : but even here, it is only approximation — not 

 identity. Mr. Owen has shown a difference between the skull of the lion and the 

 tiger, for instance. The structural distinction, however, between even the largest 

 and the smallest of this genus— between the lion and the cat — is so trifling that 

 Zoologists determine the various species by other than anatomical details. Still, 

 I cannot but think— since the only permanent character is the skeleton — that 

 wherever this principle is unrecognized, there must be perplexity. So closely are 

 the felidae anatomically allied, that Temminck considers them zoologically 

 indivisible. But what Naturalist has ever so affirmed of any genus of fishes ? 

 However nearly external appearances may approach — as they do in some of the 

 salmon species — I am bound to say that I am not aware of any instance in which 

 structural difference does not mark species ; and therefore conclude that anatomy 

 is the true basis to distinguish them. Even were not this recognised by 

 Naturalists, and an observer of fish noticed that there was a striking distinction 

 between the anatomy of different species of the same genus, he would be startled 

 to find, in the course of his researches, two so called species, in which there was 

 no structural distinction ; and would judge them to be misplaced. So would an 

 observer of the feline tribes, on finding the anatomy of various species to shew 

 very trifling differences, be surprised to detect, in two of them, a wide dissimilarity. 

 I believe no instance of this has occurred : if ever it should, the supposed species 

 would probably be removed from the genus to which it had hitherto been supposed 

 to have belonged ; and if not referable to any other, would either form a separate 

 and new genus, or hold the isolated position of an anomalite. 



