DEVELOPMENT OE PERIPATUS CAPENSIS. 
771 
those of insects and Chilopods, and never retain a nucleus ; they are about *5 millim. 
in length ; but their length is very difficult to estimate, since the excessively fine undu- 
lating terminations of their filaments are only to be followed with high powers and by 
constant alteration of focus. 
The spermatozoa met with in the ovaries were, wherever space allowed it, in con- 
stant motion. The long tails showed an undulating movement, accompanied by a spiral 
corkscrew-twisting motion. As the filaments turned round partially or wholly on their 
axis, it could be seen that they are, in their broader median part, not cylindrical and 
circular in section, but flat bands, much broader along one transverse axis than the 
other. The spermatozoa are found always twisted up into loops, which show all kinds 
of varieties of form. The commonest form is a simple loop near one end of the ribbon- 
like part of the long filament, the spermatozoon thus having one long and one much 
shorter tail (Plate LXXIV. fig. 5, i). In other cases a double loop is formed at one 
end of the ribbon ( 2 ). Sometimes the ribbon forms a loop at one end, and the two 
ends twist round one another spirally in opposite directions (3). In other cases, not so 
common, the loop is near the centre of the ribbon (4). 
Besides the glands already described there are in the male a pair of simple rod-like 
bodies lying at the hinder end of the body outside the nerve-cords, and running down 
towards the generative aperture. These bodies (Plate LXXII. fig. 3, a. g) are in the 
fresh state conspicuous from their pearly whiteness. When examined under the micro- 
scope they appeared to consist of simple tubes lined with a single layer of gland-calls. 
They are probably accessory generative glands ; but their mode of termination was not 
made out, nor was much attention paid to their structure. 
Development . — When the uterus filled with embryos was found in the first specimen 
of Peripatus dissected, it was hoped that all the stages in development, or many of 
them, might be observed amongst the many embryos in the one specimen. It was, 
however, found that the whole of the thirty or more embryos were in exactly the same 
stage, which is that shown in Plate LXXV. fig. 3. 
In only two cases were embryos found in the same mother, some of which were more 
advanced than others. In these two the period of pregnancy appeared to be just the 
same, and the embryos were just in that condition in which the first pair of members were 
turning in to become the jaws (figs. 6, 7, 8). A regular gradation showing this change 
was found in each case. No serial arrangement of the embryos of various stages in the 
uterine tubes was observed. The youngest stages in development were not met with 
in the twenty specimens dissected, though, as before mentioned, one still virgin female 
was found, and therefore the earliest stages should still have been to be met with. 
The stage apparently youngest, and in which the ovum was smallest, is that shown in 
Plate LXXIV. fig. I , a ; but the embryos in this case, or ova, appeared to have perished 
or become injured. There were very few in the uterine tubes, and they all appeared 
somewhat collapsed. In several cases embryos which had perished and become formed 
into opaque masses of fatty and fibrous tissue were met with situate in their somewhat 
shrunken uterine enlargements between other perfectly healthy embryos. 
