DEVELOPMENT. 171 



the general truth that in mental evolution as in bodily evo 

 lution the progress is from the indefinite and inexact to the 

 definite and exact. For the first statement of this induction 

 was but an adumbration of the correct statement. 



As a result of his examinations von Baer alleged 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 assemblage of organisms; that at each sub 

 sequent stage traits are acquired which successively distin 

 guish the developing embryo from groups of embryos that it 

 previously resembled thus step by step diminishing the 

 group 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. This abstract proposition will per 

 haps not be fully comprehended by the general reader. It 

 will be best to re-state it in a concrete shape. Sup 



posing the germs of all kinds of organisms to be simul 

 taneously developing, we may say that all members of the 

 vast multitude take their first steps in the same direction; 

 that at the second step one-half of this vast multitude di 

 verges from the other half, and thereafter follows a different 

 course of development; that the immense assemblage con 

 tained in either of these divisions very soon again shows a 

 tendency to take two or more routes of development; that 

 each of the two or more minor assemblages thus resulting, 

 shows for a time but small divergences among its members, 

 but presently again divides into groups which separate ever 

 more widely as they progress ; and so on until each organism, 

 when nearly complete, is accompanied in its further modifi 

 cations only by organisms of the same species; and last of 

 all, assumes the peculiarities which distinguish it as an indi 

 vidual diverges to a slight extent to the organisms it is 

 most like. 



But, as above said, this statement is only an adumbration. 



