58 



TRACHYNEIVIA DIGITALE. 



the level of the circular tube, and the small size of the digestive cavity. 

 The eight chymiferous tubes are broad, and their course can readily be 

 traced along the proboscis. The summit of the bell is quite conical ; 

 the chymiferous tubes lead into a broad circidar tube, opening into the 

 tentacles, which are hollow ; the tentacles appear to be easily lost, as 

 it is rare to obtain adult specimens in which we find anything more 

 than mere stumps in the place of tentacles. I have been unable 

 on this account to ascertam the normal number of tentacles in the 

 adidt ; they never seem to become very numerous. (See Fig. 81.) A 

 tentacle is placed opposite the base of each chymiferous tube, c, c, e, . . 

 Fig. 82, being a view from the actmal side of the yomigest Circe 

 observed ; between the chymiferous tubes there are in these young 

 MedusfB two other tentacles. We find also four marginal capsules in 

 the young as well as the adult ; their number does not mcrease with 

 age. The capsules are large, ellipsoidal, garnetrcolored bodies, enclosed 

 in a fold, standing out from the circular tube as if attached by a short 

 peduncle, {e, Fig. 83.) The veil is thick, snugly folded at the inner mar- 

 gin (Fig. 82), the larger folds extending to the circular tube. Owing to 

 the shght contractility of the bell of these Medusse, they use the veil as 



Fig. 85. 



their principal means of propulsion, bending it into the cavity of the 

 bell, and then throwing it out with great force (see Fig. 86) ; we have 

 nothing of the graceful motions of the gelatinous disk, so characteristic 

 of the Hydroid Medusse. In an adult, when seen in profile, the folds 

 of the veil are so thick that they are easily mistaken for rudimentary 

 tentacles (v, v, Fig. 83) ; it is only when we see the veil tm-ned in, or 

 expanded fully outside of the bell, that their true nature is under- 

 stood. In adult females, the cavity of the bell is almost filled by the 

 eight sausage-like ovaries Avhich hang down from near the upper part 

 of the chymiferous tubes, almost to the extremity of the gelatinous 

 proboscis. (Fig. 81.) They are of a milky color, the bell is of a slightly 

 pinkish tint ; far from being transparent, it has a horny look, and be- 



Fig. 84. Profile yievr of a young Tracliynema, about one eighth of an inch in height. 

 Fig. 85. Trachynema somewhat more advanced than Fig. 84. 



