228 HARGITT. [VOL. II. 



Concerning variation in the number and order of tentacles 

 it is difficult to determine definitely, since in Nemopsis they 

 constantly increase in number as the medusa grows, much as 

 in Margelis. So while there appears to be considerable varia- 

 tion in the number and arrangement it may be rather due to 

 variable development than to any actual meristic variation. 

 The same may be true as to the order of appearance. The 

 paired, capitate tentacles at the apex of the bulb appear uni- 

 formly first and seem to be fairly constant. The latter fila- 

 mentous tentacles appear to arise in pairs successively toward 

 the margins of the bulb. Since I was not able to follow this 

 development in the stages of growth of the medusa it is impos- 

 sible to determine definitely this point. So while there is upon 

 the preserved specimens considerable want of symmetry in 

 this respect, yet it may be due in part to slightly variable rates 

 of development. No constancy was apparent in the matter, 

 and it would seem therefore to be physiological rather than 

 morphological. 



Similarly there was apparently some variation as to the 

 number and distinctness of the otocysts upon the sensory 

 bulbs. Normally there is a single eye-spot at the base of each 

 tentacle. But in many cases they were apparently absent. 

 And while it is not impossible that they had been rendered 

 indistinct by the formalin in which they were preserved, still it 

 remains quite certain that marked differences were distinguish- 

 able among various specimens of similar size and preservation, 

 and perhaps only critical histological examination will be ade- 

 quate to finally determine this point, and this I have not been 

 able to make. 



Margelis. 



Of these medusae more than five hundred specimens have 

 been examined, most of which were quite young, having only 

 the four pairs of marginal tentacles and four unbranched oral 

 tentacles and measuring only about 0.5 mm. in diameter. Typi- 

 cally this medusa may be characterized as having a high hemi- 

 spherical bell, four radial canals, at the distal or marginal ends 

 of which four clusters of filiform tentacles arise. The bell is 



