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 oesophagus, 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 Doridida, — arteries 

 conveying the nourishing fluid to all the various organs, which fluid is returned to the 

 auricle through the skin and branchiae. That which passes through the aerating 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 bi'anchial 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 *he posterior 

 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 oesophagus, 

 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 



