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. 



