THE ANATOMY OF DORIS. 121 



In some species the testis is a loosely convoluted tube, of no 

 great extent, in others it is complicated with a fusiform mass of 

 minute, densely-packed, and convoluted tubule. Two species are 

 in addition provided with a provocative stiletto, to which is 

 attached a gland. 



The female organs are, ovarium, oviduct, and mucus-gland. 

 The ovarium is spread over the surface of the liver, in the form 

 of a branched duct with terminal ampullre. 



The oviduct is always a good deal dilated as it nears the mucus- 

 gland, is more or less convoluted, and previously to passing into 

 that organ, it has its communication first with the testis, and 

 then with the androgynous apparatus. The mucus-gland is 

 voluminous, formed of a convoluted tube arranged in two masses, 

 one imbedded in the other, the tube being differently disposed in 

 each. This gland secretes the mucous nidus for the ova, on their 

 passage from the oviduct to the exterior. 



The androgynous apparatus is a tube or vagina opening from 

 the exterior into the oviduct, having one or two diverticula 

 spermathecse communicating with it in its course. 



On the right side of the body, beneath the cloak, and not far 

 from the anterior extremity, opens a common vestibule, which 

 receives the orifices from the three parts of the reproductive organs 

 the male orifice being anterior to the others. 



In the connexion of the testes with the oviduct, we recognise 

 the channel whereby self-impregnation may be effected, which, 

 from the solitary habits of many of the species, may not unfre- 

 quently be rendered necessary. 



The spermatozoa are developed within large and fusiform sperma- 

 iophora, which are observable in the spermathec«3. The spermatic 

 filaments themselves, fully formed, are found in vast abundance in 

 the dilated part of the oviduct, they have been, likewise, detected 

 in the ovary itself. When fully grown, they are elongated, slender, 

 and waved, having at one end a small, curved, fusiform enlarge- 

 ment. 



Organs of circulation and respiration. — The circulatory organs 

 are a systemic heart, arteries, lacunae, and veins. The existence 

 of true capillaries in the liver mass seems probable. There is also 



VOL. II. PT. I. Q 



