418 Miscellaneous. 



MISCELLANEOUS. 



Oil the Heart., the Digestive Tube, and the Generative Organs of 

 Amaroecium torquatum. By M. C. Maurice. 



On examining a transverse section made about the middle of the 

 postabdomen of an Amarcecium we find three entirely empty cavities. 

 One of them, which is elongated and median, occupies the whole 

 width of the postabdomen and is situated in the horizontal plane 

 of the Ascidian ; of the other two, of irregular form, one is dorsal, 

 the other ventral. These cavities are the sections of three tubes 

 which run longitudinally in the postabdomen ; they have been 

 observed in other species of Ascidia by MM. Seeliger, von Drasche, 

 and Delia Valle, although these writers were unable to ascertain 

 their precise signification. The last two cavities were regarded by 

 M. Delia Valle as processes (peritoneal sacs) of the peribranchial 

 cavity. I have been able, in Amarcecium torquatam, to ascertain 

 the anatomical arrangement of these diff'erent organs. 



At the posterior extremity of the postabdomen the heart is situ- 

 ated. The cardiac cavity, and with it the pericardiac cavity, are 

 incurved in the form of a crescent, one of the horns of which is 

 produced into the dorsal and the other into the ventral half of the 

 postabdomen. The pericardiac cavity ascends very far on each 

 side ; each of its branches terminates ctecally at a level which varies in 

 different individuals, but generally at the level of the ovary. These 

 two branches of the pericardiac cavity are the two peritoneal sacs 

 of M. Delia Valle mentioned above. 



As regards the median tube of the postabdomen, it terminates 

 caecally posteriorly, after haA'ing bifurcated near its extremity into 

 two branches, which nearly reach the end of the postabdomen. If, 

 on the other hand, we trace this tube forward, that is to say 

 towards the viscera, it is seen to subdivide at the level of the 

 stomach into two tubes, which apply their anterior extremities 

 against the bottom of the branchial cavity on each side of the pos- 

 terior raphe, between the extremity of the endostylo and the 

 entrance of the oesophagus. These anatomical arrangements show 

 that we have here to do with the organ which MM. Van Beneden 

 and Julin have called the epicanUum, an organ which is a depen- 

 dency of the branchial sac. In adult individuals I have been unable 

 to demonstrate the actual orifices of the epicardiac tubes into the 

 branchial cavity ; but these orifices are evidently closed by secon- 

 dary obliteration in the course of the development of the animal, 

 for I have found the communications between these tubes and the 

 branchial cavity very distinct in an allied species, A. proliferum, 

 and in the young larv» of the present species, A. torquatum. 



Thus, of the three cavities which we find in a transverse section 

 of the postabdomen at the middle, the median one is a dependency 

 of the branchial cavity (epicardium) and the other two processes of 

 the pericardiac cavity. 



The cardiac cavity is open, not only at its two extremities, as in 



