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PROCEEDINGS OF THE 



[April, 1857- 



by the same means crawl about with considerable activity, until 

 they have selected a position upon which to fix themselves for the 

 rest of their existence. 



1st Group. TTJBULARIA proper. 

 Medusas without tentacula but provided with from four to eight 

 crests disposed in a radiate manner around the opening of the bell- 

 cavity. Digestive trunk quite large and surrounded by the sexual 

 oro-an. Radiate tubes four. On the outside of the disk pass up- 

 ward eight rib-like stripes which appear to contain round cells, 

 (thread-cells ?) towards the top of the disk. The medusae remain 

 fixed to the hydra from which they hang in clusters. The females 

 develop their embryos in the interior of the bell-cavity which they 

 do not leave until provided with tentacula. After discharging its 

 young in this manner the Medusa shrinks and gradually dwindles 

 away. 



2nd Group. 



Medusa like the last in general structure — but provided with 

 four tentacula — becomes free and never nurses its embryos. 



TTJBTJLAEIA CRISTATA, not: spec. 

 The pedunculated Medusa of this species is, when the disk is 

 expanded, of a rather deeply campanulate form. The digestive 

 trunk is very long and very frequently is thrust through beyond 

 the opening of the vail. It is shaped like a Florence flask, being 

 very broad near its junction with the bell, from which its outline 

 is distinguished by a constriction. The margin of the bell has 

 in this condition a lobulated appearance, and there are eight such 

 lobules, and eight external rows of thread-cells(?) which run up the 

 outer surface of the disk like meridian lines. When, however, the 

 disk is distended with embryos in course of development it has a 

 more or less spherical form, the opening of the vail being contracted 

 as if by a sphinctor, and at this time, a number of crests, from four 

 to eight, more or less elevated according to their state of expansion, 

 are observed, disposed radiately around the closed opening and 

 longitudinally with regard to the axes of the body. There are 

 no tentacula, and the crests just described appear to me homolo- 

 gous not with tentacula but with the similar and similarly placed 

 crests figured by Forbes in his iSteenstruppia and Euphysa. 

 What I believe to be the sexual organ, in which I think I have 

 seen ova with germinative vesicle and dot, is at this stage broad- 

 est and most developed at the upper part of the digestive trunk 



