22 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



from the Tripedalia about to be described. From the ovaries in this 

 form are detached masses of cells (Fig. 71) which float free in the 

 stomach pockets among the developing embryos, and to judge from the 

 vacuolation that appears, are used up in their favor. These cell masses 

 are described more fully in the part on Tripedalia. 



B: TRIPEDALIA CYSTOPHORA. 

 a. Habitat. 



The species upon which the new family was founded was obtained in 

 great abundance in one locality in Kingston Harbor in the summer of 

 1896. The environment was even more unlike that in which Cubome- 

 dusas have been found heretofore than in the case of Charybdea Xayma- 

 cana. On the west side of the Harbor there is a part more or less cut off 

 from the main body of water, and so from the ocean, by a peninsula. 

 This sheltered bay is dotted with small mangrove islands which toward 

 the head of the bay become so numerous as virtually to convert it into a 

 mangrove swamp. The water is shallow and discolored with organic 

 matter, showing that the tide does not exercise much influence here, and 

 the bottom is for the most part a black mud, deep enough to make 

 wading very uncomfortable but not impossible near shore. The islands 

 rise but slightly above the level of the waters, and the thick vegetation 

 that covers them, for the most part mangroves, grows out into the water 

 on all sides, forming a fringe of overhanging boughs. It was here in the 

 shelter of the boughs, among the roots and half -submerged stems of the 

 mangroves, that the small Cubomedusa was found to thrive. It could 

 be obtained in great abundance almost any day, and of all sizes from the 

 largest adults with stomach pockets filled with eggs or embryos down to 

 small specimens only about two millimeters in diameter. In but one 

 other place was Tripedalia found, and that was a similar region of half 

 landlocked water skirted with mangroves, situated near Port Royal, 

 across the harbor from the locality just mentioned. It would be hard to 

 find places in which the conditions of life were more strikingly different 

 from those of the pure deep sea in which the Cubomedusas have been 

 generally found before. The slight brownish yellow pigment made the 

 small medusas a little difficult to see in the discolored water, but like the 

 pellucid Charybdea in the clear water of the harbor, their active move- 

 ments gave away their presence. The swimming was very vigorous and 

 was effected by quick, strong pulsations (as many as 120 per minute were 

 counted), very different from the slow, rhythmic contractions of the 



