DIFFERENCE IN SIZE OF OVA. 47 



recognised the ontogenetic representative of the 

 spontaneously generated simple cytode, which he 

 hypothetically assumes as the first ancestor of man, 

 as well as of all other animals. To say nothing of 

 the Evolution doctrine, in the interest of which 

 Haeckel thus expresses himself, but taking his 

 comparison of the newly fecundated ovum to a 

 simple cytode as involving a question merely of 

 homology, the view appears to me an exaggerated 

 piece of transcendentalism. And not less extreme 

 in its transcendentalism is the idea that the yolk of 

 the ovum, after it has been converted into blasto- 

 dcrmic cells by division and subdivision, is the 

 ontogenetic recapitulation of a Synamcebium. The 

 globular blastoderma of the mammiferous ovum, for 

 example whether we view it in respect to its forma- 

 tion, or in respect to its wondrous though well-known 

 and verifiable potentialities when formed I hold to 

 be a very different thing from an aggregation of 

 simple homogeneous cells which can never give 

 origin to anything else than cells like themselves. 



When the ovum is minute in size, as in man and 

 the mammifera for example, the yolk is, after fecunda- 

 tion, all resolved into the cells forming the blasto- 

 derma ; but when the yolk is large, as in birds, it is 

 in part only resolved into blastodermic cells, this 

 partial resolution into cells taking place in the region 

 of the cicatricula, or spot where the germinal vesicle 

 was imbedded. The explanation of the difference 

 in size between the ovum of a bird and that of a 



