162 THE MEDUSAE. 



The manubrium is short and nearly spherical, the mouth surrounded by four 

 simple lips. 



Tentacles. — The largest number of tentacles observed was twenty-one, in 

 a specimen 8 mm. in diameter. In small specimens 2-4 mm. in diameter 

 there are from eleven to fifteen tentacles. Besides the developed tentacles 

 all the specimens, even the largest, have tentacles in process of formation, 

 which vary from small rudimentary swellings to fully formed tentacles of small 

 size. In small specimens the rudimentary knobs are about as numerous as 

 the tentacles (PI. 37, fig. l) ; but in large specimens they are fewer, one 

 specimen with seventeen large tentacles having only ten knobs, several of 

 which already clearly show that they are young tentacles. Since the knobs 

 show all stages in growth, it seems that none of them permanently retain 

 the rudimentary character seen in the knobs of E. danducnsis and U. viridula, 

 but that probably the adult specimens have fully formed tentacles only. 



All the tentacles, whether fully formed or rudimentary, are flanked at 

 their bases by a pair (sometimes two pairs) of lateral cirri (PI. 37, fig. 2), 

 but there are no cirri scattered along the bell margin such as are character- 

 istic of E. viridula. The tentacles have swollen, conical bases, and very deli- 

 cate, thread-like extremities. When fully expanded they are about as long 

 as the radius of the bell, but in the preserved specimens most of them are 

 contracted. 



Otocysts. — The otocysts are about as numerous as the tentacles (large 

 and rudimentary), and alternate with them. In the early stages in the 

 growth of a new tentacle the new rudiment is formed between the otocyst 

 and one of the tentacles flanking it, and a second otocyst is developed 

 later. Thus, succession is of course a further argument in favor of the view 

 that all the knobs in this species represent merely the early stages of devel- 

 oping tentacles. The largest number of otocysts observed was twenty-seven 

 in the specimen above mentioned which had twenty-one large tentacles and 

 eight rudimentary ones. The sense organs, which are of small size, each 

 contain from two to five or more spherical otoliths. 



Eirene mednsifera is the second known case of a Leptomedusa giving rise 

 to free medusa buds, the first being aflForded hy Eiicheilota parodoxica (Mayer, 

 : 00'', : 04), and in it, as in this latter species, the buds are developed from the 

 region of the gonads. These organs occupy the distal third of the radial 

 canals (not, however, extending quite to the bell margin) ; and are cylindri- 

 cal in form. A photograph of a gonad with several growing buds is repre- 



