THE NEW CELL DOCTRINE 



19 



significant because we must assume that almost incredibly 



small quantities of material occasion alterations in the ovum. 



C 







— *£m- 



-i 



>.-JS-. 



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/:, 



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 diflEerentiation; C, from the adult animal, 23 mm. long, after comple- 

 tion of the differentiation. — Ajler 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 



