152 ORGANIC EVOLUTION CONSIDERED 



great lengths of time is, of itself, I think, sufficient 

 evidence to prove that they are functional. If they 

 are of use in the embryos of the higher vertebrates, 

 then their existence cannot be regarded as a vestige 

 of the process of evolution — they cannot be looked 

 on as rudimentary organs. If these parts are func- 

 tional in embryonic fishes, as we presume they are 

 from their inheritance by fishes through most of the 

 geological ages, then I see no reason why they may 

 not be functional in the other classes of vertebrates. 

 In all these classes the embryo exists in an egg and is 

 surrounded by a fluid or by soft material — the most 

 striking difference to which they are subjected being 

 that of temperature. 



