Royal Blici'oscopical Society. 217 



devoid of corpuscles, unless some extraneous matter, such as zoo- 

 sperms, becomes mixed "with it, the vessels which convey it are 

 invisible. 



The heart is situated between the right lobe of the stomach and 

 the second part of the intestine. It is composed of several longi- 

 tudinal fibres which are attached anteriorly along a transverse fibre, 

 which, passing immediately in front of the right lobe of the stomach, 

 is fixed to the parietes of the body. Posteriorly they join together 

 to form a single fibre, which passing behind this lobe is in like 

 manner attached to the parietes at that point. "When the genera- 

 tive gland increases in size it pushes between the right lobe of the 

 stomach and the first part of the intestine, giving the appearance 

 as if the posterior end of the heart were fastened to its enveloping 

 membrane. I am rather uncertain whether these fibres are united 

 together by a membrane, but appearances are more in favour of the 

 idea that it is not present in this species ; at all events, the wall next 

 the stomach is deficient, neither is there a cell present at either end ; 

 Mr. Eay Lankester's opinion, therefore, that the heart is a mere 

 churning organ is so far confirmed. 



Generative Organs. — None of the specimens that I examined 

 were sufiiciently advanced to show fully-developed generative 

 organs ; in a few of the largest (0 • 72 mm. in length of body) this 

 gland contains in its substance spherical bodies of a granular aspect, 

 which only wanted a nucleus and nucleolus to resemble cells. They 

 can be squeezed out, and then float about in the surrounding liquid ; 

 I should think that they are not ova, but rather sperm-cells. 



In this paper I have given a figure of the neural and one of the 

 haemal side of the animal ; I did not consider it necessary to repeat 

 the figure of the side view given in my last paper, as it is quite 

 correct, with the exception of the omission of a tube from the 

 branchial aperture slightly backward and towards the haemal side 

 immediately in front of the stomach. 



If one may judge from published figures, the animal which 

 I have just described difiers a good deal from all the other species 

 of this genus ; but I have refrained from giving it a special name, 

 because, until we know to how much variation each species is subject, 

 it would perhaps be rash to assume that the difierences which this 

 particular specimen shows are sufficient to form a true species. 

 These difierences from Dr. Fol's 0. Dioica* which presents the 

 nearest approach to my specimens, are seen in the sbape of the 

 integument, which is not so angular, in the shape of the stomach, 

 which is more rounded, and in the shape of the tail, which is more 

 pointed at the extremity. 



* 'Mem. de la Socie'te de Phj's.,' &c., pi. iv., figs. 1-C. 



