THEIR SIGNIFICANCE IN HEREDITY. 369 



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

 the formation and expulsion of polar bodies must not be inter- 

 preted 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 idioplasm contained in the egg-nucleus is not, as a 

 matter of fact, reduced to one half, but to one quarter, inasmuch 

 as two successive divisions take place. I may add that I had also 

 considered 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 suppo- 

 sition of such a difference, and I did not wish to bring forward the 

 idea, even as a suggestion, when there was no secure foundation 

 for it. The morphological aspects of the formation of the first 

 and second polar bodies are so extremely similar that such a 

 supposition might have been considered as a mere effort of the 

 imagination. 



Hensen 1 also rejected the second part of the supposition that 

 reduction must take place in the number of the hereditary elements 

 of the egg, and that such reduction is caused by the expulsion of 

 polar bodies, because he believed it to be incompatible with the 

 fact, which had just been discovered, that polar bodies are formed 

 by parthenogenetic eggs. He concludes with these words : ' If 

 this striking fact be confirmed, the hypothesis which assumes that 

 the egg must be divided into half before maturation, is refuted, 

 and there only remains the rather vague explanation that a pro- 

 cess of purification must precede the development of the embryo.' 



1 Hensen, ' Die Grundlagen der Vererbung nach dem gegenwartigen Wissens- 

 kreis,' Zeitschr. f. wissenschaftl. Landwirthschaft, Berlin, 1885, p. 731. 



Bb 



