218 MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 
When fully developed, the ovarium is spread over the liver as a thin layer of tubes 
and follicles. The tubes are ramified from the general oviduct, and end partly in 
anastomoses, and partly in free extremities, the ramifications being all studded with 
innumerable sessile follicles. This stratum in the breeding season is very conspi- 
cuous, but is scarcely discernible at other times, and extends over the whole liver, 
with the exception of a small space on the under surface along the median line. The 
main branches of the oviduct all tend towards the anterior and upper edge of the 
liver, along which the common trunk courses from left to right. The oviduct before 
leaving the liver dips somewhat downwards ; it then quits that organ as a fine tube, 
which is at first free, and then becoming attached to the left side of the mucus- 
gland, is suddenly dilated ; it then passes sinuously on as far as the front of the 
mucus-gland, where it is found somewhat diminished in size ; it is then suddenly 
bent backwards, and again forwards, and at the second bend receives the inner end 
of the testis as above stated. It then sinks into a fissure in the opake portion of the 
mucus-gland, and being joined by the duct from the androgynous apparatus, de- 
bouches into the female channel. 
The mucus-gland is an irregular rounded compressed mass ; the left side is flatter 
than the right, and shows most easily the connexions of the different portions of the 
generative organs ; and here also it can be seen that the gland in question is com- 
posed of two parts, one semipellucid, formed of the convolutions of a large tube, the 
other opake, brownish red, imbedded in the former and made up of the closely com- 
pacted folds of a minute tube. There is a large channel in the interior of the gland 
communicating with the vulva externally, — the female channel; this receives the ter- 
mination of the convoluted tube of the gland, and also of the oviduct, after it has 
been joined by the duct of the spermatheca. 
The androgynous organs are two spermathecee and connecting channels ; one 
channel, the vagina, is large, longitudinally plicated within, leads from the common 
external vestibule, and opens freely into the principal spermatheca ; this is a globular 
sac of a purple brown colour, owing to its contents, and lies between the male and 
female parts. Just where the vagina opens into the spermatheca a small duct leaves 
it, which is soon joined by one, still smaller, from the accessory spermatheca, and 
then opens into the oviduct, where it dips into the opake part of the mucus-gland. 
The accessory is a much smaller sac than the principal spermatheca; it lies against 
the vagina, is of lighter colour than the other, and its duct is very short. 
Of the reproductive system of Doris there are two varieties, the most remarkable 
of which we shall now proceed to notice. In D. hilamellata* the testis is con- 
siderably shorter and thicker than in D. tuberculata ; it is suddenly much constricted 
at its junction with the oviduct, which is also suddenly and strikingly constricted a 
little way before it reaches the testis, and the whole of the twice bent part and its 
continuation into the opake portion of the mucus-gland is elongated, and of the 
=5= Plate XIV. fig. 8. 
