and on the Mmnmaria Manhattensis. 85 



opening situated on a short tube slightly lobed at its edge, M-ith 

 circular and radial fibres (muscles) (57 diam.).* The muscular 

 sac (mantle) of this Mainmaria is tough, and contains much pig- 

 ment. The majority of pigment cells are filled either entirely or 

 partially with yellow and brown or black molecules. The latter 

 are found at this stage of development in diverging lines from 

 the base to the back, and on the back forming a line, in the 

 middle broadest, tapering to its ends, surrounded by a light- 

 colored space. 



The orifice opens and closes at irregular intervals. The con- 

 traction of one is followed by the contraction of all others 

 imbedded within the same common envelope. 



While carefully removing the muscular sac, I ascertained 

 that the short tube leads into the branchial sac, and that its 

 internal membrane adheres to the muscular sac around the ori- 

 fice. On further examination I found that the body is sur- 

 rounded by a fibrous membrane, and that the greatest portion 

 of the body consists of the branchial sac (about f ), while the 

 heart (and a mass of different cells, among them an aggregation 

 of dark fat-cells, lying forward and near the branchial sac, and 

 a body composed also of cells), inclosed within a membrane of 

 its own, occupied the remaining space (^). 



At this stage of development there exists no intestinal tract, 

 and consequently no internal opening. 



The branchial meshes are more or less rectangular or oval in 

 shape, provided with cilise on the inside, within the canal, along 

 which red pigment is deposited, giving them a reddish appear- 

 ance, the circulation of the blo^d peculiar to the Ascidians — 

 for some time in one and after a short pause in the opposite 

 direction — was visible. N^ear the base of the tube lies the cir- 

 cular canal of the branchial sac, into which all canals, cuttino- 

 the other circular canals nearly at right angles, open, covered 



* All examinations were made on living animals ; Plossl's large microscope 

 was used. 



