16 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
both these glands when in a state of activity. In specimens where the 
eggs have not reached any considerable degree of development the 
two glands are of small proportions, appearing simply as folded sacks 
whose walls are composed of cells with deeply staining nuclei. When 
at the height of their activity, however, they are greatly enlarged, the 
second filling the larger portion of the hinder third of the animal. It 
may be noted that these two glands do not correspond very closely to 
the albuminiparous and muciparous glands described by Peck ('90) 
for Ci/mbuliopsis- calceola and "probably the Thecosomatous forms 
generally." 
About opposite the mouth of the first of the glands described above 
there opens into the common genital duct a blind sack which, from 
position, size, non-glandular wall, anfl ciliated lining (although it 
contains no sperm in any of the specimens studied), I am inclined to 
regard as a rcceptaculum seminis. This sack is of moderate pro- 
portions with a strongly ciliated inner surface. It extends backward 
towards the gonad as is shown diagrammatically in figure 12 (pi. 4). 
Below the mouth of the rcceptaculum and glands, the genital duct 
widens out into a vagina, diagrammatically represented in figure 12 
(pi. 4). In specimens where the eggs have reached a considerable 
degree of development this vaginal portion of the duct presents a 
normal appearance with ciliated inner surface and rather muscular 
walls; but just previous to the development of the eggs when sperm 
is maturing in the gonad and the penial glands (to be described pres- 
ently) are enlarged, the vagina is distended by a deeply staining sub- 
stance apparently secreted from its walls. Whether or not this 
secretion (which disappears before the eggs become mature) has any- 
thing to do Avith the transference of the sperm to the penial opening 
on the side of the head I cannot say. There is a flap-like fold at the 
mouth of the vagina that may serve to keep this secretion from es- 
caping too early. 
The penis and its two accessory glands shown in diagrammatic 
form in figure 13 (pi. 4), are small and inconspicuous in specimens 
not in a state of male activitv, but when enlarged to their full extent 
these parts are of considerable dimensions, nearly equaling in their 
combined bulk the glands connected with the hermaphroditic duct. 
In figure 6 (pi. 2) these parts have become considerably reduced in 
size. The penis itself is a tube capable of cvagination and when in 
place extends from near the opening marked po in figure G (pi. 2) 
