362 ON THE NUMBER OF POLAR BODIES AND 



But the nucleoplasm must be unequal if the products of division 

 are to develope into different parts of the embryo. In both cases, 

 however, karyokinesis is connected with a longitudinal splitting of 

 the nuclear threads, and we may conclude from this fact (which is 

 also confirmed by the phenomena of heredity) that all such nuclei, 

 whether they have entered upon the same or different ontogenetic 

 transformations of their nucleoplasm, are identical as regards the 

 ancestral germ-plasm which they contain. During the whole pro- 

 cess of segmentation and the entire development of the embryo, the 

 total number of ancestral germ-plasms which were at first contained 

 in the germ-plasm of the fertilized egg-cell must still be contained 

 in each of the succeeding cells. 



Thus no objection can be raised against the view that the four 

 loops of the first polar body contain the ovogenetic nucleoplasm, 

 that is to say, an idioplasm which contains the total number of an- 

 cestral germ-plasms, but at an advanced and highly specialized 

 ontogenetic stage. 



The formation of the second polar body may be rightly considered 

 as a ' reducing division,' as a division leading to the expulsion of 

 half the number of the different ancestral germ-plasms, in the form 

 of two nuclear loops, for no reason can be alleged in support of the 

 assumption that the four loops of the second nuclear spindle are 

 made up of identical pairs. Furthermore the facts of heredity re- 

 quire the assumption that the greatest possible number of ancestral 

 germ-plasms is accumulated in the germ-plasm of each germ-cell, 

 and thus that the small number of loops not only means an increase 

 in quantity but a multiplication in the number of different ancestral 

 germ-plasms present in each of them. If this conclusion be correct, 

 there can be no doubt that the second division of the egg-nucleus 

 means a reduction in the above-mentioned sense. 



But there are yet other observations which, if correct, must also 

 be considered as ' reducing divisions.' I refer to all those cases in 

 which the longitudinal splitting of the loops is either entirely 

 wanting, or does not occur until after the loops have left the equator 

 of the spindle and have moved towards the poles. In both instances 

 the bearing upon the question would be the same, for only half the 

 number of primary loops would reach each pole in either case. If 

 therefore the primary loops are not made up of identical pairs, it 

 follows that the two daughter-nuclei can only contain half the 



