THE NEW CELL DOCTRINE 



significant because we must assume that almost incredibly 

 small quantities of material occasion alterations in the ovum. 



-Ky 





,.'> 



FIG. 13. Muscle nuclei of the giant salamander (Necturus) in various stages. 

 A, nucleus of 7 mm. larva before differentiation; B, from a 26 mm. larva at the 

 beginning of differentiation; C, from the adult animal, 23 mm. long, after comple- 

 tion of the differentiation. After A. C. Eycleshymer. 



So soon as one spermatozoon penetrates the ovum, as is found 

 in the case of most eggs, no spermatozoa can follow. If we 



