64 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
part of the posterior third of the body, and in the preserved specimen the 
male gonopore was at a distance of less than 1 mm. from the female open- 
ing. There is a large muscular penis enclosing a spacious prostate gland 
(“ Körnerdrüse”), which communicates with the ductus ejaculatorius at the tip 
of the organ, the two ducts opening to the exterior almost together (Fig. 5). 
The ciliated ductus ejaculatorius extends along the ventral wall of the penis, 
at the posterior end of which it divides into two vesiculæ seminales, convo- 
luted tubes with muscular walls (not well shown in the diagram, Fig. 4). The 
vasa deferentia are two large convoluted canals of nearly uniform calibre which 
connect with the vesiculæ seminales at the root of the penis. There are also 
two smaller posterior seminal canals which unite with the main anterior canals 
immediately before these join the vesicule seminales (Fig. 4). As the speci- 
men was in a late stage of sexual activity, no trace of the testes could be found, 
and the vasa deferentia were only partly filled with spermatozoa. 
The female gonopore leads into a spacious bursa, from which the vagina, 
with diminishing calibre, leads upward and backward over the male organ, 
and receives the oviducts which open into it opposite to one another at a point 
above the posterior limits of the penis. The canal, which is ciliated through- 
out, and which from now on is reduced in diameter and uniform in calibre, 
passes forwards and downwards over the penis, reaching nearly to the ventral 
wall, and then bends upwards and backwards again, passing over the vagina 
and terminating a little posterior to the female gonopore in a vesicle or 
enlargement, ‘‘accessorische Blase” (Figs. 4 and 5). 
The terminology employed in the description of the sexual organ of this 
species is not that which is customarily used in descriptive anatomy of Poly- 
clads, but corresponds to the terminology applied to Triclads. The so called 
“accessory vesicle” I believe to be directly homologous with the uterus of Tri- 
clads, and that fertilization takes place in it. Although the single specimen of 
the species under consideration was far advanced sexually, there was still a 
packet of spermatozoa in the uterine vesicle, and Plehn ! has figured the uterine 
vesicle of Latocestus atlanticus containing both ova and spermatozoa. 
Diposthus corallicola, gen. nov., sp. nov. 
Figs. 6-11. 
Color, yellowish rose; very opaque except at margin, which is bluish and 
very translucent. Of the internal organs the position of the pharynx only can 
be seen as a lighter ragged median streak, Two closely approximated groups 
of eye-spots about one tenth the total length of the animal from the anterior 
end. Two pointed conical tentacles close to anterior margin. Length, 15-40 
mm. ; greatest breadth, 6-13 mm. Abundant under coral rock on reef at Hope 
Island, May 12. A very active form. 
1 Plehn, M. Neue Polycladen gesammelt von Herr Kapitan Chiercha, etc. Jen. 
Zeitschr. f. Naturw., Bd. XXX. p. 160, Taf. XI. Fig. 10, 1896. 
