ALLEGED DIFFERENTIATION OF CELLS. 4 1 



together a community to which he gives the name 

 of Synamoebium ; and that, though originally homo- 

 geneous in composition, structure, and endowments, 

 they came at last by a process of ' differentiation ' to 

 form a many-cell organism possessed of differently 

 endowed organs which all worked together for a 

 common end. 



To prove the validity of these phylogenetic 

 presuppositions, Haeckel appeals to facts which 

 ontogenesis or embryonic development, as he alleges, 

 actually brings before our eyes at the present day, 

 such as the formation of the blastodenna. This 

 membrane is composed of cells into which the 

 yolk of the egg is resolved in the process of division 

 and subdivision which takes place after fecundation, 

 which cells, though at first homogeneous, as he alleges, 

 subsequently differentiate themselves, so as to form 

 the various organs of the embryo. And thus, argues 

 Haeckel, is his biogenetic fundamental law confirmed, 

 viz., that the development of the individual is a short 

 and rapid recapitulation of that of the line. 



This argument seems to run in a circle, inasmuch 

 as it assumes that cells having been spontaneously 

 generated and having multiplied by proliferation, 

 then set to work to ' differentiate ' themselves, so as 

 to become transformed into more complex animal 

 bodies ; whilst to prove this assumption another is 

 made, viz., that the cells composing the blastoderma, 

 though at first homogeneous, afterwards ' differentiate' 

 themselves to form the more complex organs of the 



