236 THE EVOLUTION THEORY 



somes. That these increase again by division to the normal number 

 does not save the theory, for only identical ids can arise in this way, 

 while the significance of the multiplicity of the ids lies mainly in 

 their difference. The halving of the number of ids in each ' male ' 

 ovum would necessarily lead, if not to a permanent diminution in 

 the number of ids, at least to a monotony of the germ-plasm, since 

 the number of different ids would be steadily decreasing and the 

 number of identical ids as steadily increasing. This too would be 

 a contradiction of the theory. But Dr. Petrunkewitsch's investiga- 

 tions have shown that, of the four nuclei which are formed by the 

 two reducing divisions, the two middle ones (Fig. 79,712 and if 3) 

 recombine with one another, and fuse into a single nucleus, and that 



Kz % 



K? 



^""'^ '""' I k^^^ 



V 



Fig. 79 ^repeated). The two maturation divisions of the 'drone eggs' 

 (unfertilized eggs) of the bee, after Petrunkewitsch. Bsp i, the first directive 

 spindle. Ki and K2, the two daughter-nuclei of the same. Rsp2, the second 

 directive spindle. K^ and A' 4, the two daughter-nuclei. In the next stage 

 K2 and Ji 3 unite to form the primitive sex-nucleus. Highly magnified. 



from this copulation-nucleus in the course of development the primitive 

 germ- cells of the embryo arise. Now all the ids which were originally 

 present in the nucleus of the immature ovum may be reunited in 

 this ' polar copulation-nucleus ' if the two nuclei K 1 and K 3 turned 

 towards each other in Fig. 79 contain different ids. That this is 

 the case cannot of course be seen from the ids themselves, but it 

 seems to ine extremely probable, since it is dissimilar poles of the 

 two nuclear spindles which here unite, namely, the lower pole 

 (daughter-nucleus) of the upper spindle and the upper pole of the 

 lower spindle. In the first directive or polar spindle there lay 

 thirty-two chromosomes, which had increased by duplication from 

 sixteen, and of these sixteen passed over into the first i:)olar nucleus, 

 while sixteen formed the basis of the second directive spindle. These 



