MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 217 
diately within this aperture is a very short common vestibule, on the inner wall of 
which are three orifices ; an anterior, which admits of the exsertion of the penis ; a 
posterior, the vulva, leading to the female channel ; and an upper, the vagina, leading 
to the androgynous apparatus, and receiving during coition the penis of the ac- 
coupled individual. 
The organs are male, female, and androgynous. 
Male organs .- — These consist of, first, an intromittent organ, capable of being 
protruded from and retracted within the body ; and secondly, a testis. 
In Z). tuber culata, in which these organs* are most like those of Eolis, the penis 
lies in front of all the rest. When it is fully retracted within the body, we find a 
membranous pouch of a conical form attached by its base to the inner surface of the -r 
margin of the external opening for the passage of the penis ; the pouch receives at its 
apex the external end of the testis. When laid open, there is found in it, continued 
from and through the apex, a small tube continuous with the testis ; this tube runs 
down to be attached to the side of the apex of a jailer conical bag within, and 
about half the length of the other. The interspace between the cones is filled with a 
filamentous woolly-looking tissue, which fixes the inner cone and its attached tube 
in their position ; the bases of the two cones are continuous with each other at the 
inner margin of the external orifice. When exsertion takes place the inner cone is 
everted like the tentacle of a snail, forming the apparent external penis ; whilst this 
is taking place the apex of the outer is drawn after that of the inner cone, by means 
of the tube by which they are connected ; and the filamentous tissue connecting the 
two cones with a considerable portion of the outer cone, which becomes gradually 
everted as exsertion proceeds, con>e at length to be contained within the body and 
base of the fully exserted penis. The process of exsertion seems to be brought about 
by the contraction of the walls of the outer cone, in the first instance pressing upon 
the inner cone through the medium of the filamentous tissue between them, into 
which tissue some fluid, most likely the blood, may be rapidly introduced during 
venereal excitement. 
The testis is a long, simple, pale flesh-coloured, convoluted tube, the coils loosely 
bound together with filamentous tissue ; the bundle thus formed lies partly on the 
penis, and partly on the oviduct and anterior margin of the mucus-gland. The 
walls of the tube are firm, thick and muscular ; and the interior, which is of very 
small calibre, lined with a glandular membrane, the inner surface of which is beset 
with minute cells. This tube is connected at the outer end with the apex of the 
cone described as the penis, and at the other it opens into the oviduct at a sudden 
turn, which that tube makes before entering into the channel of the mucus-gland, 
not far from the vulva, an arrangement identical with that in Eolis. 
Female organs . — These are ovarium, oviduct, mucus-gland, and channel leading 
to vulva. 
* Plate XIV. fig. 7. 
2 F 2 
