DEVELOPMENT OF PEEIPATUS CAPENSIS. 
767 
formation of the knot is evidently connected with the great power of extension of the 
body already referred to as possessed by Perijpatus. The body being constantly pro- 
tracted and then again shortened, the loops of the oviduct must be constantly pushed 
up and down inside the body-cavity, and thus get knotted. In order that the knot 
should be formed, the primary loop requires to receive a single twist, and then through 
the loop thus closed by the twist a second loop of the part of the duct beneath the 
twist must be pushed up. The movements of the body soon draw the knot tight. In 
the first specimen of Perijpatus dissected, the knot was found on both sides of the body, 
in each case drawn so tight that it had to be very carefully loosened with forceps before 
its exact nature could be made out. In the one drawn for me by Mr. Wild there was 
a knot only on one side of the body as figured ; but it is represented much looser than 
it was in reality, in order to show the way in which it runs. The knot was found in 
about ten other specimens, in some cases on one side, in others on both. It is evident 
at once to what pathological complications such a knotting of the duct must give 
rise. As the embryos swell, the uterus will become constricted at the knot, and the 
embryos will be unable to be extruded. In one of the largest specimens dissected this 
very thing had occurred, and in consequence the loops of the uterus on both sides had 
become dilated into wide sacs, which had lost all the normal successive constrictions 
originally separating the embryos from one another, and were filled with the decom- 
posed remains of embryos and masses of fatty matter. The two sacs had lost all con- 
nexion with the lower parts of the uterine canals, these having apparently mortified off 
at the knots, and were attached only to the ovary. The remnants of the lower parts of 
the uterine canals were short and empty, having probably discharged their ripe contents 
before their upper portion perished. 
The structure of the ovary is shown in Plate LXXIV. fig. 1 ,a. It is composed of a 
stroma, fine fibres with numerous small rounded nucleated cells containing granules, 
and other clear round cells, with neither nucleus nor granular contents, and other elon- 
gate nucleated cells like those seen in the figure in great abundance in the oviduct. 
The ovary has in it two elongate sacs separated from one another by a median septum ; 
and in nearly all the pregnant specimens examined, the sacs were found crammed with 
spermatozoa felted together into masses, as seen in the figure. Pear-shaped sacs hang 
from the margins of the ovary in which the ova are developed. 
The ripe ovarian ova are about T7 millim. in diameter. They have a thin trans- 
parent vitelline membrane, which encloses them within the sacs. They have an abun- 
dant finely granular yelk, a large, very transparent clear spherical germinal vesicle, and 
a finely granular germinal spot, which has a somewhat irregular outline. Some of the 
full-sized ovisacs are to be seen containing irregularly shaped masses of yelk, without 
any germinal vesicle. The ovary contains between thirty and forty ova. The ova 
appear to ripen all at about the same time. Stages in the development of the ova were 
observed in one female specimen which contained no spermatozoa, in which none of 
the ova had reached maturity. These are represented in Plate LXXIV. fig. 1, b, c, d. 
MDCCCLXXIV. 5 L 
