Organs in certain Pulmog aster opo da. 95 
prostate in P. corneiis, the follicles, instead of being massed 
into a compact gland^ as in the latter, being spread out and 
separated over a large surface; a branch artery runs up 
through the midst of these follicles, which, on a transverse 
section, might be taken for a duct. The follicles contain 
large cells, which are full of bright granules, and having at 
one end a circular nucleus ; they measure about -0030'' long. 
The two ducts at the anterior termination of the oviduct 
separate from each other_, the section into which the pros- 
tate pours its secretion leading directly into the free part of 
the vas deferens, v\^hich goes to join the penis, its point of 
entrance into that organ forming a line of partition between 
it and the flagellum. The oviduct soon opens into the 
side of the duct of the spermatheca by a nipple-like projec- 
tion ; which from this point to its entrance into the vestibule 
may be called the vagina ; it receives the ducts of the two 
multifid vesicles just before its termination. 
The spermatheca is a globular sac, situated close to the 
anterior extremity of the albumeniparous gland, beneath the 
pericardium; it has a tolerably long duct, which, just before 
it becomes the vagina, has attached to it a diverticulum, 
much longer and larger than itself; which is attached by con- 
nective tissue to the oviduct, and terminates close to its 
commencement, and was described by Swammerdam as open- 
ing into it. During copulation the penis projects into the 
duct of the spermatheca, nearly as far as the entrance of the 
diverticulum ; immediately after copulation the spermatheca- 
duct and its diverticulum are found to be full of mature 
zoosperms ; generally there is a sort of spermatophore, first 
described, I believe, by Carus; it is a long horny ribbon^ 
longitudinally rolled together, tapering at each end, swollen 
in the middle, and there containing a mass of zoosperms ; 
this appears to get into the spermatheca, and then to be 
broken up. 
The dart-sac has thick muscular walls, which consist of 
transverse and longitudinal fibres, the former being princi- 
pally internal, the latter external ; the dart is four-cornered, 
and appears to be secreted from a papilla at the bottom of 
the sac. These darts are occasionally to be found buried 
among the viscera; for instance, I have found two darts 
close to the albumeniparous gland in one case ; in another^ 
one dart was found in the interior of the duct of the sperma- 
theca. The dart-sac opens into the vestibule to the right of 
the entrance of the vagina, the opening being guarded by a 
raised margin. The walls of the vestibule are studded with 
spicules of carbonate of lime; it opens externally, close to 
