﻿240 CONTRIBUTIONS TO THE NATURAL HISTORY 



this ao-ain from the upper portion, c, of the tube, which enlarges into a central cavity, d. 

 This tube, or proboscis, when contracted, does not extend beyond half the depth of the 

 main cavity of the body. It is even at times shortened beyond this limit. In its utmost 

 state of contraction (Plate V. Fig. 10), the lower opening, o, is rather widened, and the 

 proboscis may then be compared in some degree to the mouth of other Medusa?, though 

 its margin, «, is not split into lobes. When relaxed, it either hangs straight downwards or 

 forms undulations in its course, and hangs then generally, not only to the lower margin of 

 the main cavity, but more or less beyond. (Plate V. Fig. 7, 8, 9, 11; also, Plate IV. 

 Fi°\ 1, 6 to 12.) When greatly elongated, it may even hang between the tentacles, for 

 as great a length as the greatest diameter of the body itself. 



The upper part of the tube, c, c, c, in the centre, is always thinner than the middle and 

 lower portions. To this middle part, b, b, b, the eggs are attached. But before examining 

 minutely the structure of this apparatus, let us follow it further. From the central cavity 

 (Plate V. Fig. 7, d), into which the proboscis empties, arise four chymiferous tubes 

 (Plate IV. Fig. 1, 2, 3; Plate V. Fig. 1 and 3, g,g,g,g; 7 and 11, e, e, e, e), at right 

 angles with each other, which communicate freely with the central cavity, as well 

 as with the cavity of the proboscis. These four tubes, following the inner surface of the 

 gelatinous disk, extend to its lower margin, where they are united with each other 

 by an annular tube of the same appearance and the same diameter, forming a cir- 

 cular canal (Plate IV. Figs. 1, 2, 3; Plate V. Fig. 11, k,k) around the lower part 

 of the disk, and this circular tube communicates as freely with the vertical radiating 

 tubes, as those communicate with the central cavity ; so that digested materials and 

 water, by which the food is dissolved, and with which it is mixed in greater or smaller 

 quantity, circulate freely to and fro in all this apparatus. It is astonishing how 

 quickly an animal, swallowed by this little Medusa, is dissolved, and its particles cir- 

 culated. The digestion takes place above the mouth, which shuts over the food, or is 

 simply stretched upon the surface of the animal upon which it feeds, sucking its juices 

 and dropping soon after its dead carcass. In that way the Sarsia swallows very quickly 

 large numbers of other small Medusa?, and especially of the young of Aurelia aurita, and 

 also other soft animals and small Crustacea ; I have, however, never seen it swallowing 

 the hard parts of any of these latter, but only sucking their juices between these lobes. 



This liquid food moves on through the proboscis in jerks to and fro, under the con- 

 tractions of the tube. It even takes some time for the contents of the stomach to pass 

 entirely into the central cavity, into which they are pushed on, mingled with more 

 or less water. But there is a constant process of regurgitation taking place, so that par- 

 ticles which were once near the upper end of the proboscis are now and then suddenly 



