INDIAN NUDIBRANCHIATE MOLLUSCA. 125 
rounded a little, hollowed in front, and bifid behind. There are no distinct hepatic 
ducts, the stomach apparently being formed in a great measure by the expansion of 
their trunks. The walls of the cavity, however, have a peculiar honeycombed appear- 
ance, caused perhaps by a rudimentary condition of those conduits. 
The intestine passes from the upper wall of the stomach, at some little distance behind 
the cesophagus, and penetrates the liver as a tube of no great size or length; it turns 
almost immediately backwards, and terminates in a large anal nipple in the usual posi- 
tion amidst the branchial plumes. 
The reproductive organs do not present any very striking peculiarity. The male 
intromittent organ is extremely small, and the glandular tube in connexion with it is 
divided into two portions ; that next the penis, or outer portion, is small and convoluted ; 
while the inner portion is much wider, and has an extremely minute convoluted tube 
within it. The ovary is spread over the anterior portion of the liver, and, in addition to 
the large mucous gland, there is a small folliculated gland attached to the female outlet. 
The vascular system appears to be as complete as it is in the Doridide,—arteries 
conveying the nourishing fluid to all the various organs, which fluid is returned to the 
auricle through the skin and branchize. That which passes through the aérating organs is 
derived entirely from the great hepatic vein, which drains the liver, stomach, and ovary. 
All these organs combine to form one single mass, within which the circulation appears 
to be complete. The hepatic vein passes backwards from the liver on the median line, 
and opens into the inner or afferent branchial channel, which is of a crescentic form, 
arched forwards, with the limbs passing close round each side of the anus. The 
branchial arteries open into this channel, and, passing up the inner surface of the gill- 
plumes, communicate through the leaflets with the branchial veins, which run down 
the opposite or outer side of the plumes. These veins debouch, on the other hand, 
into an outer, crescentic, efferent branchial channel, which opens into the posierior 
lateral angles of the auricle by two large orifices, one a little on either side of the 
median line. The blood returned through the skin is drawn from the general lacunary 
system. It is conveyed by a lateral pallial channel on either side of the back, and 
enters the anterior lateral angles of the auricle. 
The nervous centres are characterized by extreme concentration—the cerebroid, 
branchial, and pedal ganglions forming a fused mass around the base of the proboscis. 
They exhibit also in a notable manner the globular structure so frequently observed in 
the Mollusca. The buccal ganglions are placed on the under side of the cesophagus, 
close to the true salivary glands ; they are connected with the cerebroids by extremely 
long commissures, so as to allow the necessary action to the proboscis. 
The above account of the anatomy of this genus has been drawn up entirely from 
Doridopsis gemmacea: the other species examined show no remarkable divergence in 
their structure, with the exception of D. miniata, in which there is no anterior stomach 
or crop, the gullet being continued backwards almost to the posterior extremity of the 
