ANACANTHINI 151 



vertebrate characters implies closer affinity with the proximate 

 cold-blooded class, so a higher character of organization may- 

 be predicated of the palaeozoic Placoids and Ganoids than of 

 the Ctenoids and Cycloids forming the great bulk of the class 

 at the present day. The comparative anatomist dissecting a 

 shark, a Polypterus, or a Lepidosteus, would point to the 

 structures of the brain, heart, generative organs, and in the last 

 two genera to the air bladder, as being of a higher or a more 

 reptilian character than the corresponding parts would present 

 in most other fishes. But the palaeontologist would point to 

 the persistent notochord, and to the heterocercal tail in palaeo- 

 zoic and many mezozoic fishes, as evidence of an " arrest of 

 development," or of a retention of embryonic characters in 

 those primaeval fishes. 



No class of animals is more valuable in its application to 

 the great point now mooted by the Uniformitarians and Pro- 

 gressionists of the present day than that of fishes ; for they 

 are exempt from the attack of the Uniformitarian on the score 

 of the defective nature of negative evidence, to which attack 

 conclusions from the known genetic history of air-breathing 

 animals are open. Many creatures riving on land may never 

 be carried out to sea ; but marine deposits may be expected 

 to yield adequate grounds for general conclusions as to the 

 character of the vertebrate animals that swarmed in the seas 

 precipitating such deposits. 



One other conclusion may be drawn from a general retro- 

 spect of the mutations in the forms of the fishes at different 

 epochs of the earth's history, — viz., that those species, such as 

 the nutritious cod, the savoury herring, the rich-flavoured sal- 

 mon, and the succulent turbot, have greatly predominated at 

 the period immediately preceding and accompanying the 

 advent of man ; and that they have superseded species which, 

 to judge by the bony Garpikes (Liyidosteus}, were much less 

 fitted to afford mankind a sapid and wholesome food. 



