402 PROCEEDINGS OF THE ACADEMY OF [Sept., 



ingly similar sections were made throue:h the same region in individuals 

 of both species, and neglecting individual variation the series showed 

 some interesting relations of organs decidedly unlike those just noted. 

 From the study of specimens of smaller size it was found that between 

 1.5 and 3 cm. in length the renopericardial canal and gonoduct undergo 

 a considerable amount of displacement. By referring to fig. 4, repre- 

 senting a section through an individual 3 cm. long, it will be seen that 

 the right renopericardial canal and gonoduct have their apertures facing 

 each other. Material of this size gave very satisfactory results with 

 both species, and a study of sections of animals from 1.5-3 cm. long- 

 made it readily possible to trace where these organs go in assuming the 

 adult condition. 



In individuals 1.5 cm. long the renopericardial canal, which opens 

 into the gonoduct near its end, gradually shifts forward to open by the 

 latter by a common lipped mouth. From this stage on the common 

 mouth of the canal and duct appears to change its position very little, 

 if at all. At the same time the gonoduct, in some inexplicable way. 

 forms for itself a second outlet into the kidney, a short distance away 

 from the original mouth. It is this last named opening that is shown 

 in fig. 4, and the one that in the adult serves for the discharge of the 

 sex products. 



The above statements are interesting not only in themselves, but 

 they appear to me to explain certain other statements lately made. 

 Tobler ('01) reported a second communication between the gonoduct 

 and kidney in Parmophorus, and was followed by Totzaur ('02) with 

 the statement that he had found a similar state of affairs in Haliotis. 

 Neither of these investigators gives the point any explanation ; never- 

 theless I believe both cases may come under the above interpretation. 



Blood System. — In the following discussion of the organs of circula- 

 tion an attempt has been made to explain certain apparently incorrect 

 statements regarding this genus. Generally speaking the broader 

 features of the system are already known. The work of Milne Edwards 

 ('47), Lacaze Duthiers and especially Wegmann ('84) have done much 

 to advance our knowledge along this line. Briefly reviewing their 

 work in the light of the California species, it may be said that the 

 heart is situated on the left posterior side of the visceral mass, a little 

 behind the mantle cavity. The two auricles open into the ventricle, 

 pierced V)y the rectum, and ventricular valves prevent the backward 

 flow of blood. A small anterior aorta (fig. D. Ao) supplies blood to a 

 portion of the mantle on the left side. The first part of its course is 

 upon the dorsal wall of the rectiun. 



