98 



Mr. L. Doncaster. 



[Sept. 21, 



the egg margin as polar bodies. Such a process would not be very different 

 from what occurs in the saw-flies and other Hymenoptera, but Henking 

 confesses that he has never actually seen this second polar mitosis. " Die 

 Theilung muss ausserordentlich rasch verlaufen ; denn .... habe ich hier 

 immer gefunden, dass die Theilung der Chromosomen bereits voUendet war." 

 Like Henking, I have had difficulty in observing this second polar division; 

 although stages with three groups of chromosomes and a developing 

 pronucleus are abundant. It is clear that the outer and inner groups left 

 from the first polar division do not divide simultaneously, and although 

 I have many sections of these stages I have no clear figure of the division 

 of the inner group, i.e. of the separation of the female pronucleus from the 

 chromosomes of the second polar body. For some time I doubted whether 

 any such division occurred, but the presence of three groups of polar 

 chromosomes is difficult to explain without it, and I have obtained a few 

 sections which suggest that such «, division is taking place. It clearly 

 occurs before the division of the outer chromosome group, for while the 

 latter is still a confused mass near the edge of the egg, the inner group 

 often appears very much drawn out (Plate 2, figs. 26, 30) as if undergoing 

 division, and in other sections (fig. 31) the division is seen completed. 

 This stage seems to follow immediately on the first division, so that 

 the division of the inner group of chromosomes is part of the same 

 process as the original separation into inner and outer groups. In Plate 2, 

 fig. 29, a different phase is represented, in which the inner group looks 

 as if it were forming a compact mitotic figure, but this appearance is not 

 usual. 



After the chromosomes which will give rise to the female pronucleus have 

 sunk in to some extent, the outer group of chromosomes, lying near the 

 edge of the egg, undergoes an irregular division (Plate 2, fig. 32), so giving 

 rise to three groups altogether of polar chromosomes, but these are so 

 confused and irregular that the number in each group is never ascertainable 

 with certainty, and it appears as if some fusion often takes place between 

 them (fig. 33). 



There is one possibility which should be mentioned here, wliich is not 

 entirely inconsistent with any of my sections. It is that the three groups 

 of polar chromosomes are all derived by division of the outer group left by 

 the first maturation division. T have no section wliich proves with 

 certainty that the inner rod-like chromosomes descrilMMl above are not 

 converted direct into the female pronucleus, and that tlic! three groups of 

 polar chromosomes are not produced by a separation of the original outer 

 group into two, followed by a second division of tlie outermost, and so 



