MUSEUM OF COMPARATIVE ZOOLOGY. 173 
had originated there. The dorsal sac was moderately large, and con- 
tained numerous spermatozoa, which were, however, scattered, and not 
in groups. I do not know how to explain this case, unless indeed it be 
due to a rupture of the dorsal sac in places, and the consequent evacua- 
tion into the body cavity of a part of its contents. Although I did not 
find any point at which this could be shown to be unmistakably true, 
yet there were many places where the wall could not be distinguished ; 
furthermore the body was in this case much distorted in killing. Even 
when the outlines of the sac are plainest, one always finds spermatozoa 
in the body cavity in greater or less numbers ; so, for example, in the 
cavity of the terminal organ (Plate IV. Fig. 53). This, so far as I 
know, is the only fact which favors the view that their place of origin 
is in the body cavity; aside from this, the evidence points to the dorsal 
sac as testis. A further study of additional material is necessary to 
determine finally this point, as well as many others. 
The external sexual organ of the male consists of the terminal pa- 
pilla to which reference has often been made. It has much the shape 
of a slightly curved truncated cone (Fig. 53) with an opening at the 
smaller base, and with the larger base joined to the body obliquely, so 
that it naturally turns ventrad. The length and curvature of the organ 
vary a little, as can be seen from the different figures (Figs. 4, 9, 53, 89, 
90). The essential features of its structure can be made out from a total 
preparation in clove oil (Fig. 53). The muscular layer of the body wall, 
which for some distance has been growing thinner, stops suddenly along 
a well defined line. Beyond this only the hypodermis lies between the 
cuticula and the body cavity. The cuticula, which is here a little thicker 
than usual (see also Plate VII. Fig. 90) is infolded at the end of the or- 
gan and runs forward as the lining of the cavity for a variable distance. 
I was at first inclined to believe that this infolded portion could be to a 
limited extent extruded and then drawn in; but further study seems 
to show that it cannot. The thick cuticula is too stiff to be rolled in 
or out without being folded somewhere, yet on sections it is always 
smooth; moreover, there is no muscular provision for moving the organ 
in this way. At its anterior end the cuticular infolding is continous 
with a sac (va. df.) having delicate walls, and this is in turn connected 
with the dorsal sac previously described (Fig. 53 and Plate VI. Fig. 89, 
va. df.). Although I plainly saw and drew in several cases the walls of 
this connecting portion from clove oil preparations, yet they are so deli- 
cate that in sections they were not once preserved except as loose shreds 
of tissue. I was consequently unable to ascertain whether there was 
