DEVELOPMENT OF THE CAPE SPECIES OF PERIPATUS. 177 
It is interesting to notice here the small size (‘04 mm.) of 
the ovum of the West Indian species as described by Kennel. 
The eggs of these three species seem to form a perfect series in 
regard to size! and amount of yolk, and it would be extremely 
interesting to compare their structure and the early stage of 
their development. I regret, however, the materials for this 
comparison are to a great extent wanting; for, although we 
know more of the development of the West Indian species than 
of the New Zealand one, thanks to the researches of Kennel, 
still, as I have pointed out in my former paper (this Journal, 
vol. xxv), the latter are too incomplete to permit of any profit- 
able comparison. 
After this account of the general structure of the ovum of 
the Cape species, I will describe the special features of the 
unsegmented uterine ovum at its different stages. 
The unsegmented ova, which I have found, seem to belong 
to two distinct stages, each of which presents special features. 
There are (1) the stages before the conjugation of the male and 
female pronuclei; (2) the stages after that event. 
1. The ova of this stage all belong to P. Balfouri; they 
are distinguished externally by the small size of the dark area 
in the living ovum (vide Part 1, Pl. XXXI, fig. 2), and by the 
apparent absence, in surface views, of the polar bodies. All of 
them, at least all those of which I succeeded in preparing good 
sections, presented indications, more or less distinct, of a male 
pronucleus, and in all polar bodies were being formed. 
The ovum contained an irregular central cavity which, how- 
ever, was not so well marked as in later ova. The reticulum 
was slightly denser round the nucleus than elsewhere. This 
slight increase in density is the cause of the small opaque spot 
in the fresh ovum. The nucleus was placed in the middle of 
the long axis of the ovum near the surface, and presented a 
different structure in every ovum of this stage which I examined. 
1 Greatest length of ovum of P. nove zealandiex, 15 mm.; of P. 
capensis, ‘5—6 mm.; of P. Balfouri, -4—5 mm.; of P. Edwardsii, 
‘04 mm. All the known species of Peripatus are viviparous and bring forth 
fully developed young. 
