146 THE ANATOMY OF AMPHIPTYCHES URNA. 
those which have previously been described as present in the yelk glands. It appears 
as if these, as it were, ‘‘ran together,’ and formed a case enclosing certaim of the 
nucleated cells, some of which are ova, and some probably cells from the yelk glands 
(cf. Fig. 9), which will serve as food yelk for the developing ova. This appears to be 
the only construction which can be placed upon the appearances. 
As before said, at an early date in the formation of ova and food yelk, whilst 
they are within the structures which respectively give rise to new supplies of each, 
there is a very close resemblance between the two. 
In the other worm, previously referred to, the embryos are in a much more highly 
developed state. The shell is less evident, and evidently less resistant as the stain 
has penetrated. An embryo is represented in plate 13, figure 13. It is oval in form; 
the body seems to be composed of a syncytium, with very numerous nuclei on the 
outer surface. Within the external layer strands of protoplasm containing fewer 
nuclei pass across the centre of the body. The anterior end is marked by the 
possession of a circlet of ten spines, which, when fully formed, have each the shape 
of a crescent attached to a long straight piece. In development (Fig. 7, a, 0, c, d) 
the crescent piece is the first formed, and the longer straight portion appears later on 
as a small outgrowth, which gradually increases in length. 
Receptaculum seminis.—This is the structure previously referred to as having been 
described by Wagener as testis. It forms a small saccular body lying in close contact 
with the central structure containing ova. (Pl. 11, Fig.1,7.s.; and Pl. 12, Fig. 7, 7.s.) 
From its dorsal side there passes posteriorly a long single median duct, the walls of 
which consist of long ridges of cells enclosed within a connective tissue coat. The 
duct runs along the median line dorsal to the uterus, and, passing backwards, 
stretches beyond the uterus and vesicula seminalis, turns to the left, and opens 
dorsally shghtly in front of the level of the male opening (Pl. 11, Fig. 1,7. s. 0.). 
The duct is a very distinctly marked structure, and receives no branches of any kind. 
The receptaculum is full of ripe spermatozoa, and amongst these are found some 
very deeply staining nucleated cells; these were present in all three specimens of 
which sections were cut (Pl. 12, Fig. 7, x.), and they have in general appearance and 
the way in which they take stain, a marked resemblance to the ova. Possibly they 
may be simply the sperm blastophores from which the ripe spermatozoa have been 
separated, but such structures were not clearly made out, and there is no proof of 
this. I am strongly inclined to think that there is a connection between the recepta- 
culum and the central space containing ova, though my sections do not allow me to 
determine this with certainty. On plate 12, figures 1, 2, 3, 4, 5, and 6, a series of 
drawings are given representing the structures as seen in a series of consecutive 
