612 MARCQS M. HARTOG. 



The reduction so effected is purely quantitative, and appears 

 to involve male as well as female cells. (The grounds on 

 which this thesis is founded are referred to below.) 



4. '' Noyaux de rebut" and fertilisation-nuclei are absolutely 

 equivalent; their respective fates are determined by the ac- 

 cident of position. 



5. By the last mitosis both " noyaux de rebut" and fertilisa- 

 tion nuclei cease to be true nuclei, capable of indefinite 

 normal evolution, and are simple pronuclei, only possessing 

 restricted powers of development. 



6. The peculiar characters of the pronuclei are due then to 

 the preliminary double mitosis ; they can only accomplish 

 their functions by union (copulation) with a nucleus from a 

 different germinative cell. 



7. Normal copulation can take place between two pronuclei, 

 and two only.^ 



8. The copulating nuclei, though of distinct origin, are 

 equivalent to one another, and either plays the same part to 

 the other. In the nuclear union, the supreme act of fecunda- 

 tion, there is neither male nor female ; the sexual modifications, 

 which are so obvious to our eyes, are mere accessory adaptations 

 to facilitate and ensure the approximation of the pronuclei, 

 which themselves are of no sex at all. Fecundation, reduced to 

 its lowest terms, is distinct from and independent of sexuality. 



9. The high evolution of these accessory sexual adaptations 

 is only a proof of the extreme physiological importance of the 

 nuclear copulation in fecundation. 



10. The chromatin of the nuclei represents their permanent 

 personality ; the other nuclear structures are subject to con- 

 tinual changes, destructive and recuperative, and only play an 

 accessory part. 



11. The act of fecundation is completed by the union of the 

 chromatic elements of the two pronuclei into one single 

 nucleus, and this union may be effected at different stages 

 of nuclear evolution. 



' Maupas seems ignorant of the many cases of "multiple isoganiy"in 

 Protophjtes : see "Some Problems of Reproduction," in this Journal. 



