24 MUSEUSr, BKOOKLYN INSTITUTE OF ARTS AND SCIENCES. 



In addition to the tentacles there are about sixty-four bluntly rounded 

 papilla? upon the bell-margin. 



There are sixty-four otocysts, a pair on either side of the origin of each 

 and every one of the short, straight tentacles. Each otocyst contains a sin- 

 gle spherical otolith. 



There are four straight narrow radial canals and twenty-eight diverticulse, 

 which extend inward from the circular vessel, and end blindly in the gelatin- 

 ous substance of the bell. The otocysts flank the sides of these radial canals 

 and diverticulfe (see Fig. 53). 



The four gonads are papilliform and are developed upon the outer halves 

 of the four radial canals (see Pig. 59) 



The manubrium is tubular, cruciform in cross section and elongate, and 

 has four recurved lips. It extends about three-quarters of the distance from 

 the inner centre of the bell cavity to the velar opening. 



The gelatinous substance of the bell is of a delicate greenish yellow. The 

 entoderm of the manubrium gonads and tentacle bulbs is opaque yellow-green, 

 with the innermost parts purple. There are four interradial, reddish purple, 

 pigment spots upon the manubrium near the points of origin of the radial 

 canals. The nematocyst-warts upon the short tentacles are either white or 

 dark purple, while the half-rings on the long, flexible tentacles are red and 

 yellow. 



Development of Medusa: The youngest medusae (Fig. 50, Plate V) ob- 

 served were about 0.7 mm. in diameter, the bell being higher than a hemi- 

 sphere and the exumbrella surface regularly besprinkled with nematocysts. 

 There were eight tentacles, four radial and four interradial. These all be- 

 longed to the short, straight, "adhesive" set and projected from the sides of 

 the bell above the bell-margin. There were only four otocysts, one at the base 

 of each interradial tentacle. The radial canals were narrow and straight- 

 edged, and the circular vessel was simple without centripetal diverticulae. The 

 manubrium was quadratic, and very short. 



As the medusa grows its bell increases in height relatively faster than 

 in width, so that it becomes higher than a hemisphere and resembles in shape 

 the bell of Bougainvillia. When 3 mm. high (Fig. 51, Plate V) there are 

 still only eight tentacles, but the radial canals have become broad with serrate 

 edges, and four interradial diverticulse begin to develop from the circular vessel. 

 The eight tentacles have greatly elongated and terminate in simple nematocyst- 



