368 ON THE NUMBER OF POLAR BODIES AND 



such minute processes, do indeed prove that the number of loops 

 is reduced to one half. It has been already mentioned that, ac- 

 cording to Carnoy, such reduction occurs in Ascaris megalocephala, 

 but the same author also describes the process of the formation 

 of polar bodies in a large number of other Nematodes 1 , and his 

 descriptions show that the process occurs in such a way that the 

 number of ancestral germ-plasms must be reduced by half. Some- 

 times half the number of primary loops pass into the nucleus of the 

 polar body, while the other half remains in the egg. In other 

 cases, as in Ophiostomum mucronatum, the primary nuclear rods 

 divide transversely, a process which must produce the same effect. 

 It is true that these observations require confirmation, and since, 

 with unfavourable objects, the difficulties of observation are ex- 

 tremely great, there may have been errors of detail ; but I do 

 not think that there is any reason for doubting the accuracy of 

 the essential point. And this essential point is the fact that the 

 number of primary loops is divided into half by the formation of 

 the polar body. 



But even if we could not admit that such a conclusion is securely 

 founded, it cannot be doubted that the formation of the second polar 

 body reduces to one half the quantity of the nucleus which would have 

 become the segmentation-nucleus in the parthenogenetic develop- 

 ment of the egg. This is a simple logical conclusion from the 

 two following facts : first, parthenogenetic 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 egg requiring fertil- 

 ization remains in the egg when it is to develope parthenoge- 

 netically, 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 assump- 

 tion that the formation of the nucleus of the second polar body 

 must be considered 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 genera- 

 tion. When, in 1885, 1 brought forward my theory of the conutinuity 



1 Carney, 'La Cytodierfese de 1'ceuf; la vesicule germinative et les globules 

 polaires chez quelques N5matodes.' Louvain, Gand, Lierre. 1886. 



