OVUM IN THE CAPE AND NEW ZEALAND PBEIPATUS. 279 



In addition to the minute yolk-spherules scattered through 

 the protoplasm^ there are a few larger bodies lying just below 

 the shell, wjjich stain deeply, have a homogeneous structure, 

 and are probably of a yolky nature. The cells of the lower 

 end of the stalk have begun to grow round the outside of the 

 egg so as to form a follicle, which at this stage extends round 

 about one third of its circumference. 



The nucleus, as is shown in fig. 6, next becomes irregular 

 in outline, and is thrown into folds, which project into the sur- 

 rounding protoplasm. These projections, with depressions 

 between them, occur all round the nucleus. This change in 

 the nucleus is probably the forerunner of its total disappear- 

 ance, which in the next stage will be described as having dis- 

 appeared, though I have not been able to observe the further 

 steps in the process in this species. In P. Balfouri, how- 

 ever, I have a further stage in its disappearance, in which the 

 nuclear wall is completely lost, the position of the nucleus being 

 indicated by a dense mass of protoplasm, which at its edges is 

 continuous with the loose protoplasmic reticulum of the egg, 

 and which contains in its centre some irregular chromatic 

 particles : this condition is shown in fig. 7. By a still further 

 diffusion and breaking up of this dense mass of protoplasm, it 

 is easy to conceive how the nucleus and even its former 

 situation might become invisible. 



In the next stage the nucleus is invisible, and the follicle 

 completely surrounds the egg, consisting of a layer of flat cells 

 which closely adhere to the eggshell; just within the egg- 

 shell a few irregular, rather deeply-staining aggregations are 

 present in the protoplasm of the ovum. These may be the 

 remains of the nucleus which have become scattered through 

 the egg, since no such aggregations are present in the former 

 stage in which the nucleus itself was visible. 



The next stage is shown in fig. 8. It differs from the last 

 only in the fact that the follicle does not adhere to the egg- 

 shell, but is separated from it all round, so that the ovum lies 

 loose in a hollow vesicle, which is attached to the ovary by a 

 long thin stalk. At this stage the cellular nature of the follicle 



