5O THE DOCTRINE OF DESCENT. 



germ at a period when the type has not yet manifested 

 itself. This led him to the question, "Whether, at the 

 beginning of development, all animals are not essen- 

 tially alike, and whether a common primordial form 

 does not exist for all ? " " It might," he finally thinks, 

 " be maintained, not without reason, that the simple 

 cyst-like form is the common fundamental form from 

 which all animals are developed, not merely in idea, but 

 historically." 



When the barrier which it was formerly thought 

 necessary to erect between asexual multiplication and 

 multiplication caused by fecundation had been recog- 

 nized as non-existent, and it was perceived that all 

 development amounts to the multiplication and meta- 

 morphosis of the primitive germ or egg-cell, the cell 

 was necessarily regarded, in the acceptation of the older 

 investigators, as the common fundamental form. But 

 although the descriptive history of evolution does not 

 go back v to this elementary organism, and considers 

 even the bifurcation as merely a preparation for actual 

 development, at any rate the earliest rudimentary larval 

 conditions of different types may be compared with 

 each other. 



The discoveries of the last ten years with reference 

 to this subject are so numerous, and such striking 

 analogies have been advanced, that we must needs go 

 much further than, at that time, was possible for Von 

 Baer. It is not merely a question of those general 

 analogies in the segregation of tissues from an indiffer- 

 ent rudimentary mass, but of homologies in the distri- 

 bution, form, and composition of the embryos and larvae, 

 of which the after effects are of profound importance 



