OCELLATE HYDRO-MEDUSA. 41 



greater than the diameter of the umbrella, but in preserved 

 specimens they are usually much contracted. 



5. The stomach, or manubrium (Figs. 21 and 25,/") 

 which is suspended from the inner surface of the umbrella, 

 or sub-umbrella, and hangs down into the sub-umbrellar 

 cavity. The manubrium consists of: 



a. Four dichotomously-branched oral tentacles (Figs. 

 21 and 25, g), upon the manubrium. 



b. The mouth, an opening situated between the bases 

 of these tentacles, and serving to put the cavity of the 

 manubrium into communication with the cavity of the sub- 

 umbrella. 



c. The body, or manubrium proper, with its central 

 cavity, or stomach. 



6. The chymiferous tubes: a set of prolongations of the 

 stomach into the substance of the umbrella. This system 

 consists of four radial tubes, and a circular tube. 



a. The four I'adiating chymiferous tubes (Figs. 21 and 

 25, i) run outwards and downwards from the point where 

 the manubrium hangs from the sub-umbrella, and they 

 may be traced down to the free edge, just above the inser- 

 tion of the velum. They lie near the sub-umbrellar sur- 

 face, but the\' are entirely surrounded b}' the gelatinous 

 substance of the umbrellit. Observe that the}' are equi- 

 distant and sepanited from each other by an arc of 

 ninety degrees. Obsene, too, that each of them lies 

 in the same place with one of the bunches of radial ten- 

 tacles. 



b. The circular ch}Tniferous tube (Figs. 21 and 25, k) 

 runs around the free edge of the umbrella just above the 

 insertion of the velum. 



c. Notice that the radiating tubes open into the circular 

 tube, so that the whole system is in direct communication 



