THE RECAPITULATION THEORY 335 



mere increase in the amount of food yolk in the 

 egg may lead to the omission of important ancestral 

 stages. 



The question then arises whether it is not 

 possible, or even probable, that animals which now 

 show no indication of degeneration in their develop- 

 ment are in reality highly degenerate, and whether 

 it is not legitimate to suppose such degeneration to 

 have occurred in the case of animals whose affinities 

 are obscure or difficult to determine. It is more 

 especially with regard to the lower vertebrates that 

 this argument has been employed ; and at the pre- 

 sent day zoologists of authority, relying on it, do 

 not hesitate to speak of such forms as Amphioxus 

 and the Cyclostomes as degenerate animals, as 

 wolves in sheep's clothing, animals whose simpli- 

 city is acquired and deceptive rather than real and 

 ancestral. I cannot but think that cases such as 

 these should be regarded with some jealousy. 

 There is at present a tendency to invoke degenera- 

 tion rather freely as a talisman to extricate us from 

 morphological difficulties ; and an inclination to 

 accept such suggestions, at any rate provisionally, 

 without requiring satisfactory evidence in their 

 support. 



Degeneration of which there is direct embryo- 

 logical evidence stands on a very different footing 

 from suspected degeneration, for which no direct 

 evidence is forthcoming ; and in the latter case the 

 burden of proof undoubtedly rests with those who 

 assume its existence. The alleged instances among 

 the lower vertebrates must be regarded particularly 



