114 AMPHIMIXIS OR ESSENTIAL MEANING OF [XII. 



mation of the nucleus of the latter into the female pronucleus, it 

 is very probable that the two nuclei would conjugate just as if 

 a fertilizing sperm-nucleus had penetrated. If this were so, the 

 direct proof that egg-nucleus and sperm-nucleus are identical 

 would be furnished.' ^ Boveri succeeded in accompHshing this 

 a few years later, although he made use of the nuclei of two 

 spermatozoa instead of those of the ova. 



I also hold, in opposition to the rejuvenescence theory, that 

 there is no polar antithesis, and that, in the union which is the 

 essence of fertilization, the nuclear loops contribute neither 

 male nor female principle, but a paternal and maternal substance, 

 and that the significance of fertilization is nothing more nor less 

 than a minghng of the hereditary tendencies of father and 

 mother. 



I. The Significance of the Process of Maturation of 

 THE Germ-cells. 



The Maturation of the Ovum, 



Relying on the views set forth above, I have made the attempt 

 to substitute a new explanation of the formation of polar bodies 

 in the animal ovum for that which has hitherto found acceptance. 

 If that substance which is expelled from the ripe ovum in the 

 polar bodies be not the male principle, what can it be ? 



The cellular nature of the polar bodies has been demonstrated 

 by Giard, Butschli, and O. Hertwig ; van Beneden has shown 

 that they contain chromatin, and that at each of the two divi- 

 sions which give rise to the two polar bodies, half of the chro- 

 matosomes leave the ^gg in the nucleus of a polar body. If 

 then the chromatin be the idioplasm, the material basis of here- 

 dity, or, in other words, that substance which determines the 

 nature and essence of the cell and its descendants, then cells of 

 different kinds must contain correspondingly different varieties 

 of idioplasm. Hence my theory of germ-plasm may be ex- 

 pressed as follows : — The fertilized ovum contains germ-plasm 

 in its nucleus, i. e. idioplasm endowed with the collective 

 hereditary tendencies of the species : at each of the cell- 

 divisions by means of which the ovum developes into the 

 organism, this idioplasm splits into two quantitatively similar 



1 Vol. I. pp. 252, 253. 



