PHIALUCIUM COMATA. 159 



being from thirty-nine to fifty and from twenty to twenty-two respectively. 

 This divergence seems to indicate the existence of two distinct varieties of 

 the species. The number of tentacles, although variable, is about the same 

 in both collections. In specimens 12 mm. in diameter the knobs have 

 largely increased in number, there being as many as sixty-two; but the 

 largest number of tentacles observed was nineteen. It appears, then, that 

 no great further increase in tentacles is to be looked for ; and therefore 

 it is almost certain that the great majority of knobs in this species, as in 

 P. virens and P. carolinae, never develop into tentacles. The tentacles are 

 short, with swollen basal bulbs, and are flanked with from one to three 

 pairs of lateral cirri (PL 37, fig. 10). The same is likewise true of the 

 larger knobs. The small knobs, however, have no cirri. 



Otocysts. — The sense organs are so large and prominent (PI. 37, fig. 9), 

 that I suspected at first that they might be open; but a study of sections 

 has demonstrated that they are merely closed vesicles of large size. It is 

 impossible to tell the normal number of otoliths on preserved specimens. 

 The number of otocysts is variable, but apparently always small, and not 

 subject to increase with the later growth of the medusa. In the two 

 largest Pacific specimens, 5 mm. and 6 mm. in diameter, there are fourteen 

 and nine respectively. In West Indian specimens the numbers counted 

 are: — 3.5 mm., seven otocysts; 7 mm., eleven otocysts; 12 mm., nine 

 otocysts; 12 mm., ten otocysts. They are irregularly arranged, in several 

 cases three in one quadrant, with only one in the adjoining quadrant, 

 while in one individual one quadrant altogether lacked otocysts. 



The manubrium is short, and flask-shaped ; the mouth is surrounded 

 by four slightly crenulated lips. 



Gonads. — The gonads first appear as small globular swellings at the 

 middle points of the radial canals, and with the growth of the medusa 

 they grow distally. In the largest Pacific individual they occupy the 

 central one third of the canals; and in the still larger West Indian 

 specimens they extend out nearly to the extremities of the canals. They 

 remain linear, however, increasing but slightly in thickness, while even in 

 small specimens large ova are to be seen. Their general appearance, 

 therefore, apart from size, gives no clue to the stage of development of 

 the specimen. The collection contains both males and Eemales. 



Color. — In life the gonads in both collections were slightly greenish, 

 but the specimens otherwise were colorless. 



