116 DARWmiANA. 



the most striking class of exceptions, if such they be, 

 seems to us even more favorable to the doctrine of 

 derivation than is the general rule of a pure and sim- 

 ple ascending gradation. We refer to what Agassiz 

 calls prophetic and synthetic types; for which the 

 former name may suffice, as the difference between 

 the two is evanescent. 



" It has been noticed," writes our great zoologist, " that cer- 

 tain types, which are frequently prominent among the repre- 

 sentatives of past ages, combine in their structure peculiarities 

 which at later periods are only observed separately in different, 

 distinct types. Sauroid fishes before reptiles, Pterodactyles be- 

 fore birds, Icbthyosauri before dolphins, etc. There are entire 

 families, of nearly every class of animals, which in the state 

 of their perfect development exemplify such prophetic rela- 

 tions. . . . The sauroid fishes of the past geological ages are an 

 example of this kind. These fishes, which preceded the ap- 

 pearance of reptiles, present a combination of ichthyic and 

 reptilian characters not to be found in the true members of this 

 class, which form its bulk at present. The Pterodactyles, which 

 preceded the class of birds, and the Ichthyosauri, which pre- 

 ceded the Cetacea, are other examples of such prophetic 

 types." — (Agassiz, "Contributions, Essay on Classification," 

 p. 117.) 



Now, these reptile-like fishes, of which gar-pikes 

 are the living representatives, though of earlier ap- 

 pearance, are admittedly of higher rank than common 

 fishes. They dominated until reptiles appeared, when 

 they mostly gave place to (or, as the derivationists 

 will insist, were resolved by divergent variation and 

 natural selection into) common fishes, destitute of rep- 

 tilian characters, and saurian reptiles — the intermedi- 

 ate grades, which, according to a familiar piscine say- 



