380 ON THE NUMBER OF POLAR BODIES AND [VI. 



nucleus which would have become the segmentation-nucleus in 

 the parthenogenetic development of the &gg. This is a simple 

 logical conclusion from the two following facts : first, partheno- 

 genetic eggs expel only one polar body; secondly, there are 

 eggs (such as those of the bee) in which it is absolutely certain 

 that the same half of the nucleus — which is expelled as the 

 second polar body in the ^%^ requiring fertilization— remains 

 in the &%g w^hen it is to develope parthenogenetically, and acts 

 as half of the segmentation-nucleus. But this proves that the 

 expelled half of the nucleus must consist of true germ-plasm, 

 and thus a secure foundation is laid for the assumption that the 

 formation of the nucleus of the second polar bod}^ must be con- 

 sidered as a ' reducing division.' 



I was long ago convinced that sexual reproduction must be 

 connected with a reduction in the number of ancestral germ- 

 plasms to one half, and that such reduction was repeated in 

 each generation. When, in 1885, I brought forward my theory 

 of the continuity of the germ-plasm, I had long before that time 

 considered whether the formation and expulsion of polar bodies 

 must not be interpreted in this sense. But the two divisions of 

 the egg-nucleus caused me to hesitate. The two divisions 

 did not seem to admit of such an interpretation, for by it the 

 quantity of the nucleus is not divided into halves, but into 

 quarters. But a division of the number of ancestral germ- 

 plasms into quarters would have caused, as was shown above, 

 a continuous decrease, leading to their complete disappearance ; 

 and such a conclusion is contradicted by the facts of heredity. 

 For this reason I was led at that time to oppose Strasburger's 

 view that the expulsion of the polar bodies means a reduction 

 of the quantity of nuclear substance by only half. My objection 

 to such a view was valid when I said that the quantity of idio- 

 plasm contained in the egg-nucleus is not, as a matter of fact, 

 reduced to one half, but to one quarter, inasmuch as two suc- 

 cessive divisions take place. I may add that I had also con- 

 sidered whether the two successive divisions might not possess 

 an entirely different meaning, — whether one of them led to the 

 removal of ovogenetic nucleoplasm, while the other resulted in 

 a reduction in the number of ancestral germ-plasms. But at 

 that time there were no ascertained facts which supported the 

 supposition of such a difference, and I did not wish to bring 



