266 J. T. CUNNINGHA.M. 



which is provided with strong cellular walls, and a canal run- 

 ning through its axis, occurs in the cavity of the heart. The 

 organ projects with its posterior half, at the end of which is 

 the broad entrance opening into the axial canal, into the intes- 

 tinal sinus, and is here, by means of special small muscular 

 bundles which arise from processes round the opening, fastened 

 on to the intestinal epithelium. The front end of the organ 

 contains the anterior opening of the axial canal and is fastened 

 to the anterior wall of the heart. 



From this account it follows that the blood passes in at one 

 end and out at the other of the heart organ of Polyophthalmus, 

 while as yet no opening at all has been demonstrated in the 

 cardiac body in the families above mentioned. 



I have been unable to find any facts which go to support 

 H orst's view that the cardiac body is homologous with an organ 

 which exists in some of the Enchytrseidse, and which arises as 

 an evagination from the intestine. The account given by 

 Salensky 1 of the development of the cardiac body in the larva 

 of Terebella is not very full, but he states that the cadiac body 

 is at first a tube passing from the posterior extremity of the 

 heart and terminating blindly in its interior ; and this tube, 

 from his description and figure, seems to have an opening from 

 the exterior posterior surface of the heart. It would seem 

 probable, therefore, that the cardiac body in Terebella is derived 

 from an invagination of the wall of the heart, and not from 

 the intestine. It is quite certain that in the adult Trophonia 

 there is no connection between the cardiac body and the intes- 

 tinal epithelium, closely as they come into relation. I cut a 

 continuous and complete series of longitudinal vertical sections 

 through the posterior part of the heart of Trophonia, and the 

 intestine it rested upon, and found that there was nowhere any 

 connection between the intestinal epithelium and that of the 

 cardiac body. 



If Horst's view were correct one would be tempted to 

 homologise the cardiac body of Cheetopoda with the cellular 

 structure which grows out from the intestine and projects into 

 1 " Etudes sur le Devel. des Aunelides," ' Arch de Biol.,' iv. 



