22 MUSEUM, BEOOKLYN INSTITUTE OF ARTS AND SCIENCES. 



tentacle, there is a large adhesive disk, while beyond this the extremity of 

 the tentacle bends at a right angle to the main shaft. This extreme tip of 

 the tentacle bears a large grape-like cluster of nematocyst cells (see Fig. 49). 



The remaining 50-60 tentacles arise from the bell-margin at a lower level 

 than the zone of origin of the adhesive tentacles. They are somewhat flex- 

 ible, and project downward rather than outward. They have no adhesive 

 disks, but are provided with 25-30 rings of nematocysts and terminate in a 

 knob-like cluster of nettling cells (see Fig. 48). 



There are about thirty-five otocysts each containing a single spherical 

 otolith ( Fig. 47 ) . These otocysts all arise from the bell-margin close to the 

 bases of the marginal (non-adhesive) tentacles. They project downward 

 freely into the water. The velum is well developed. The circular vessel is sim- 

 ple and narrow and without centripetal diverticulse. There are four straight 

 narrow radial canals; upon the mid regions of which are the papilliform 

 gonads (see Fig. 45). The manubrium is flask-shaped and there are four 

 simple cruciform lips (see Fig. 46). The entoderm of the manubrium, gonads, 

 and circular canal is dull rosin yellow. There are four green entodermal pig- 

 ment spots upon the manubrium near the points of junction of the four radial 

 canals. The internal endoterm of the bases of the adhesive tentacles is rich 

 magenta-purple, while an intense green color extends a short distance out- 

 ward into the endotermal shaft of the tentacle. The bases of the non-adhe- 

 sive tentacles are dull green without the magenta color. 



This medusa is very active, swimming rapidly with a few powerful pul- 

 sations, and then slowly sinking down with tentacles outspread. It often 

 attaches itself to objects by means of its adhesive disks. 



Development of the Medusa: In a specimen 1 mm. in diameter (Fig. 43), 

 the bell was higher than a hemisphere and the exumbrella surface regularly 

 sprinkled with nematocysts. There were sixteen tentacles. The radial and 

 interradial tentacles had as yet no adhesive disks but terminated in simple 

 nematocyst knobs. The eight intermediate tentacles, however, had such 

 disks, a condition exactly the reverse of which was observed in a young 0. 

 geophila from Key West (see Bull. Mus. Comp. Zool. Harvard College, Vol. 

 XXXVII, No. 2, PI. 5, Fig. 10). There were only four otocysts at this stage, 

 and the manubrium was rudimentary. 



When 6 mm. in diameter (Fig. 44) the bell is hemispherical. There are 

 about twenty sucker-bearing tentacles alternating with an equal number of 



