10 LILIAN SHELDON. 
strands connecting the two being clearly visible. I have 
found the male pronucleus in this condition in three ova of 
P. capensis. 
I have seen no ova of P. capensis in which the union of 
the pronuclei is taking place, though I shall shortly describe 
one of P. Balfouri, in which the male and female pronuclei 
lie close together in the centre of the ovum, and are apparently 
about to conjugate. In the next stage of P. capensis the 
union has apparently taken place, and the nucleus is a large 
lobed structure lying some little way from the periphery. It 
is not surrounded by a large and definite mass of denser pro- 
toplasm, but only by a very narrow layer, which almost imme- 
diately passes off into the loose reticulum which fills up the 
rest of the ovum. 
In the next stage the segmentation nucleus is fully formed ; 
it lies near the periphery, and is surrounded by a specially dense 
mass of protoplasm, which, as Mr. Sedgwick (15) has stated, 
causes the dark patch which is seen on these ova, by means of 
which, even after preservation, the pre-segmentation ova can 
be readily distinguished from those in which the segmentation 
nucleus is present. I have not figured ova of this stage, as 
Mr. Sedgwick (15) has already done so (v. Pl. XII, figs. 8 
and 11). 
PERIPATUS BALFOURI. 
The phenomena connected with the maturation and fertili- 
zation of the ovum in P. Balfouri are very much the same 
as in FP. capensis, and therefore I shall merely describe the 
differences between the two, and one or two stages which I 
have found in the former, which were wanting in the latter. 
Structure of the Ovary.—A section through one half 
of the ovary is shown in fig. 22; its structure in the main is 
the same as that of P. capensis, but the germinal area is 
much narrower, being confined to a narrow strip along the 
outer side of each ovarian tube. The non-germinal epithelium 
is also very much thinner; and, in fact, has the appearance of 
a membrane with small bulgings on it caused by the nuclei. 
