LORD SALISBURY ON EVOLUTION. 569* 



implications agreeing exactly with the implications pointed out 

 above. 



Once more there are the facts of embryology. In various ways 

 these tell us with endless repetition the same story. 



Von Baer "found that in its earliest stage, every organism has the 

 greatest number of characters in common with all other organisms in their 

 earliest stages; that at a stage somewhat later, its structure is like the 

 structures displayed at corresponding phases by a less extensive multitude 

 of organisms; that at each subsequent stage, traits are acquired which suc- 

 cessively distinguish the developing embryo from groups of embryos that 

 it previously resembled thus step by step diminishing the class of embryos 

 which it still resembles ; and that thus the class of similar forms is finally 

 narrowed to the species of which it is a member." 



Obviously these groups, dividing and subdividing into smaller 

 ones as they diverge and re-diverge, correspond completely to the 

 groups within groups which the classifications of animals and 

 plants show us, and with the groups within groups of the buried 

 branch, which symbolize both their relations and the relations of 

 fossil forms, so far as we know them. That is to say, what we 

 may call the embryological tree corresponds with the classifica- 

 tory tree, and with those more modern parts of the paleontologi- 

 cal tree which we have been able imperfectly to trace. Moreover, 

 if we accept the hypothesis of evolution, the strange transforma- 

 tions undergone by a developing embryo become intelligible, 

 though otherwise unintelligible. Every superior animal com- 

 mences as a nucleated cell, a form common to the smallest and 

 simplest creatures, the Protozoa. While, among the Protozoa, 

 this nucleated cell, by undergoing fission gives rise to others 

 which part company (which derived cells again divide and part 

 company), the trait common to the Metazoa is that, instead of 

 parting company, the cells formed by successive fissions remain 

 together and constitute a cluster. The members of this cluster 

 divide into two layers, between which, in higher types, there 

 arises a third ; and from these all the external and internal organs 

 are formed. In each great class of Metazoa, further development 

 of each higher type is accompanied by a " recapitulation " of traits 

 distinctive of lower types. In the Vertebrata, for instance, the 

 embryo of a bird or a rabbit has, at one time, traits resembling 

 those of the fish-embryo structures roughly representing gill- 

 clefts being one. And in the case of the human embryo, it is only 

 after exhibiting successive kinships of organization to lower 

 mammals, that it at last assumes the form proper to man. Mar- 

 velous as is this repetition of traits belonging to lower types, 

 rudely indicated, it is quite congruous with the hypothesis of evo- 

 lution implies a kind of transcendental heredity. On the other 

 hand, the hypothesis of design furnishes no explanation, but pre- 

 sents an insurmountable difficulty. For if the development of the 



