OVUM IN THE CAPE AND NEW ZEALAND PERIPATUS. 295 



presence points to its possessing any special function, since I 

 am not able to trace any such, and it appears to be completely 

 absorbed before the disappearance of the nucleus, and does not, 

 as Blochmann (5) describes in Neritina fluviatilis, break 

 up and given rise to the chromatin particles of the nuclear plate. 



Disappearance of the Germinal Vesicle. 



The existence of a stage in the ripening of the ovum in 

 ■which no nucleus is visible has now been described in almost 

 all eggs whose maturation has been at all completely investi- 

 gated. In many of these cases the mode of disappearance has 

 not been observed, but in most of those in which the process 

 has been seen it is similar to that which I have described in 

 Peripatus capensis and P. Balfouri, namely, that the 

 nucleus loses its round shape, its outline becomes irregular, 

 and by the loss of its membrane its contents mingle with and 

 finally become indistinguishable from the protoplasm of the 

 egg. Between this stage and that at which the nucleus is 

 again visible, when it is small and in the spindle stage about 

 to bud ofi" the second polar body, there is no trace of the ger- 

 minal vesicle in the ovum. I wish here to draw attention to 

 the fact that my observations were made on complete series of 

 sections of well-preserved ova, so that the probability of my 

 having overlooked it is not great. This mode of disappearance 

 has been described by Henking (10) in Phalangeden, and by 

 Stuhlmann (17) in a considerable number of insects. The 

 loss of the nuclear membrane is also described by Scharff (13) 

 as occurring in some osseous fishes, although he does not state 

 that all trace of the nucleus disappears. Lankester (12) also 

 describes a stage in the ovum of Sepia in which no germinal 

 vesicle is present. 



Blochmann (5) describes in Neritina fluviatilis the loss 

 of the nuclear membrane, and consequent mingling of the 

 nucleo- and egg-plasma, but states that the germinal spot 

 remains, and, breaking up, gives rise to the chromatin of the 

 nuclear plate. This certainly cannot be the case in the Cape 



