144 THE ANATOMY OF AMPHIPTYCHES URNA. 
surrounded by a very well developed layer of circularly disposed muscle fibres, and 
opens close to the margin of the body on the conical papilla previously mentioned, 
which is hence to be regarded as the male genital opening (Pl. 11, Figs. 1 and 4, m.0.) 
The vesicula seminalis opens into the tube leading to the exterior on a small well- 
marked papilla with muscular walls. Probably the tube itself is eversible. 
(b) Female Organs.—The most prominent structure in the body is the coiled 
tubular uterus, occupying the central part of the body, and described by Wagener as 
the ‘ eierstock.” 
Ovary.—This consists (Pl. 11, Fig. 1, ov.) of two parts, (1) a series of 
small somewhat grape-like ovaries, occupying much the same relative position in 
the body at the anterior end which the testes do at the posterior. From the 
scattered ovaries ducts unite on either side into a common one, passing into a 
centrally placed, somewhat saccular organ, filled with ova. It would appear that 
this holds the same relationship to the ovaries which the vesicula seminalis does to 
the testes ; that is, the ova are developed in the scattered ovaries and then pass into 
this central part, in which they are stored, and subsequently, perhaps, undergo 
maturation, and possibly even fertilisation in this position. In the worms examined, 
the ovaries of the three obtained by myself were in a different state of development 
from that of those in the specimen for which I am indebted to Dr. Haswell. In the 
first mentioned the ova were evidently passing down into the uterus, in which they 
were but very slightly developed. The ovaries, consequently, were full of fully 
formed ova, haying the nature of distinct cells with clearly defined nuclei. In the 
second the uterus was full of much more highly developed embryos, and no ova, 
apparently, were passing into it. In this case the ovaries were evidently in the act 
of developing a fresh supply of ova. Hach consisted of a mass of protoplasm, 
containing nuclei, evidently dividing up rapidly, whilst the outhne of the cells could 
only here and there be distinguished with anything approaching to clearness (Pl. 13, 
Fig. 11). Hach little ovary has thus, when the ova are not fully formed, the structure 
of a polynuclear mass of protoplasm, which only subsequently becomes divided up 
into a number of distinct cells (Pl. 13, Fig. 8). 
Yelk Glands.—These consist of innumerable dark-brown coloured little spherical 
masses (Pl. 11, Fig. 1., (Y/k.), which are smaller than either the testes or ovaries. 
They are distributed plentifully along the sides of the body, passing into and distending 
the folds, and at the anterior and posterior end pass across from one side to the other, 
both dorsally and ventrally. They lie always just within the circular muscle layer, 
and hence much more superficially than either the ovaries or testes. This position 
is constant. specially towards the anterior end they are united by fine tubes, - 
rendered evident by their brown contents, and on each side the ducts unite, just as 
in Trematodes, to form a common duct passing towards the median line where the 
