Anatomy of Doris. 157 



cardiac end of the stomach — a small laminated pouch. A 

 rudimentary pancreas is attached in some species to the 

 cardiac, in others to the pyloric end of the stomach. The 

 intestine is short, of nearly the same calibre throughout, 

 rather sinuous in its course, and terminates in a nipple- 

 formed anus in the centre of the branchial circle. 



The reproductive organs are, male, female, and hermaphro- 

 dite. The male organs consist of penis and testes ; the latter 

 is connected with the former and with the oviduct. The 

 female organs are, ovarium, oviduct, and mucous gland. The 

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

 of a branched duct with terminal ampillae. The oviduct ter- 

 minates in the mucous gland. The androgynous apparatus is 

 a tube or vagina opening from the exterior into the oviduct, 

 having one or two diverticular spermathecce communicating 

 with it in its course. On the right margin of the body, near 

 the front, is a common opening, to which converge the three 

 parts of the reproductive organs. The spermatozoa are de- 

 veloped within large and fusiform spermatophera, and are 

 observed in the spermathecae, oviduct, and ovary. 



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. A second heart, a ventricle, having a portal cha- 

 racter, is also described. The systemic heart lies imme- 

 diately beneath the dorsal skin, in front of the respiratory 

 crown, and comprises an auricle and ventricle inclosed 

 within a pericardium. In the systemic circle, the blood is 

 returned to the heart without having passed through the 

 special respiratory organ. It is that blood only which is 

 returned from the liver mass that circulates through the 

 branchiae. 



The authors conclude from their observations, that in the 

 molluscs there is a triple circulation : first, the systemic, in 

 which the blood propelled along the arteries to the viscera 

 and foot is returned, with the exception of that from the liver 

 mass, to the heart through the skin ; there it becomes par- 

 tially aerated, the skin being provided with vibratile cilia, 

 and otherwise adapted as an instrument of respiration : se- 



