402 BRITISH SPECIES OF BEROE. 



ed. The upper extremity of each vesicle was open, 

 and terminated on the surface, on each side, in the 

 space between two ribs. From each side of the ve- 

 sicle, near its connection with the central vessel, 

 there arose a tube, which, after dividing, sent a 

 branch to each contiguous rib. The cavity of these 

 tubes, at their union with the ribs, appeared to be 

 filled with a whitish-coloured pulp. Each rib is 

 furnished with a tube, uniting with it near the mid- 

 dle. 



In consequence of this peculiar structure, I could 

 easily observe the water enter the tube at the sum- 

 mit, pass into the lateral vesicles, and go out at their 

 external openings ; and, in some cases, the motion of 

 the current was reversed. There did not appear to 

 be any external opening at the extremity of the 

 tubes joining with the ribs, although water obvi- 

 ously moved backwards and forwards in them. 

 While the animal was active, there were numerous 

 small spaces in the different tubes where the con- 

 tained fluid circulated in eddies. This was parti- 

 cularly observable towards the centre, and in the 

 tube which descends from the summit. I was un- 

 able to detect, with the naked eye, any structure in 

 the tubes which could produce these partial motions ; 

 and the orbicular form of the animal prevented the 

 application of high magnifiers. The outline of the 

 body, given in Plate XVIII. fig. 3. and of the in- 

 ternal vessels, fig. 4. will convey to the reader an 

 idea of the parts described. 



