120 ORGANIC EVOLUTION CONSIDERED 



there is no apparent break in the strata, and there- 

 fore no evidence of lost record, and yet the advance 

 is immense. It is impossible to account for this un- 

 less we admit paroxysms of more rapid movement of 

 evolution — unless we admit that when conditions are 

 favorable and the time is ripe for a particular change, 

 it takes place with exceptional rapidity, perhaps in a 

 few generations." * 



Huxley says, in the address already quoted from: 

 " The Amphibia and Pisces tell the same story. 

 There is not a single class of vertebrated animals 

 which, when it first appears, is represented by ana- 

 logues of the lowest known members of the same 

 class. Therefore, if there is any truth in the doctrine 

 of evolution, every class must be vastly older than the 

 first record of its appearance upon the surface of the 

 globe. But if considerations of this kind compel us 

 to place the origin of vertebrated animals at a period 

 sufficiently distant from the Upper Silurian, in which 

 the first Elasmobranchs and Ganoids occur, to allow 

 of the evolution of such fishes from a vertebrate as 

 simple as the Amphioxus, I can only repeat that it is 

 appalling to speculate upon the extent to which that 

 origin must have preceded the epoch of the first 

 recorded appearance of vertebrated life." 



From the above it is evident that Le Conte believes 

 in paroxysmal evolution in which great advances in 

 structure take place in a short time, while Huxley be- 

 lieves in slow changes which carry the history of fishes 

 and other classes of vertebrates back to a period 

 immensely remote from the oldest known fossils of 

 those classes. 



The former assumes that in the case of the early 

 fishes the record is comparatively complete, while the 

 latter claims that most of it is lost. I have no doubt 



* Elements of Geology, p. 345. 



