DEVELOPMENT OF PERIPATUS NOV2E-ZEALANDI2E. 287 
cavity is marked c in the figure. It ends blindly in front and 
behind, and probably is homologous with the area which Mr. 
Sedgwick (1) calls the polar area in P. capensis, which, both 
in position and structure, it closely resembles, with the excep- 
tion of the fact of its being filled with yolk-spheres in the 
New Zealand species. Fig. 7 passes through the posterior 
end of the primitive streak, where it is thinning out, and the 
groove is much shallower. These three sections bear a very 
close resemblance to figs. 25 and 26 of Mr. Sedgwick’s second 
paper on the Cape species (1). The peripheral nuclei in the 
region of the blastopore and primitive streak have a more or 
less columnar form instead of lying flat against the side as 
they do over the rest of the ovum. The anterior part of the 
egg is enveloped in a single layer of flat nuclei. 
In an ovum of a slightly later stage the blastopore has 
increased a little in length, the primitive streak is much 
larger and more marked, the nuclei being very closely packed, 
and the primitive groove is considerably deeper ; the so-called 
polar area has disappeared. This stage is the latest which 
was present among the January eggs, except some quite old 
embryos which were almost ready for birth. 
I have examined several series of sections of older embryos, 
i. e. in which they were developed, but have not thought it 
necessary to give an account of them, as the process of 
development seems to be similar to that of P. capensis de- 
scribed by Mr. Sedgwick (2). 
The only point of interest in which it differs from that species 
is that the first somite (i. e. that of the prseoral or antennal 
segment) opens by a duct to the exterior in precisely the same 
way and position as do those of the third to fifteenth segments, 
so proving it to be the nephridium of the segment with the 
same relations as those of the posterior ones. This is shown 
in figs. 10 and 11 ; in the former the opening of the duct to the 
exterior just outside the nerve-cord is shown, and in the latter, 
which is separated from the former by three sections, its opening 
into the somite. The probability of the nephridial nature of 
this somite was pointed out by Mr. Sedgwick. 
