PROPHETIC TYPES AMONG ANIMALS. 177 



ages are an example of this kind. These Fishes, which 

 have preceded the appearance of Eeptiles, present a com- 

 bination of ichthyic and reptilian characters, not to be 

 found in the true members of this class, which form its 

 bulk at present. The Pterodactyles 1 which preceded 

 the class of Birds, and the Ichthyosauri 2 which pre- 

 ceded the appearance of the Cetacea, are other examples 

 of such prophetic types. These cases suffice, for the 

 present, to show that there is a real difference between 

 embryonic types and prophetic types. Embryonic types 

 are in a measure also prophetic types, but they exemplify 

 only the peculiarities of development of the higher repre- 

 sentatives of their own types ; while prophetic types 

 exemplify structural combinations observed at a later 

 period in two or several distinct types, and are more- 

 over not necessarily embryonic in their character, as, for 

 example, the Monkeys in comparison with Man ; while they 

 may be so, as in the case of the Pinnate, Plantigrade, and 

 Digitigrade Carnivora, or, still more so, in the case of the 

 pedunculated Crinoids. 3 



Another combination is also frequently observed among 

 animals, when a series exhibits such a succession as exem- 

 plifies a natural gradation, without immediate or necessary 

 reference to either embryonic development or succession 

 in time, as the Chambered Cephalopods. Such types I 

 call progressive types : 4 



Again : a distinction ought to be made between pro- 

 phetic types proper and what I would call synthetic types, 

 though both are more or less blended in nature. Pro- 

 phetic types proper are those, which in their structural 



1 CUVIER (G.), Oss. foss., vol. 5, 4 AGASSIZ (L.), On the Difference 

 p. 2. between Progressive, Embryonic and 



2 CUVIER (G.), Oss. foss., as q. a. Prophetic Types, etc., Proc. Am. Ass. 



3 See above, Sect. 25. Adv. Sc.; Cambridge, 1849, p. 432. 



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