182 



DIPEJRENA CONICA. 



shaped row of large elliptical cells surrounding the upper end of the 

 Fig, 303. terminal cavity, these cells being sur- 



mounted by a thick coating of small 

 granular cells, extending along the sur- 

 face of the tentacle until they gradually 

 disappear ; these granular cells are pig- 

 ment-cells, giving the terminal club a 

 reddish tinge ; the sensitive swelling at the base of the tentacles is 

 colored by similar cells, the eye-spot being black. 



This species differs from the Dipurena strangulata in the form of 

 the bell, the proportions of the digestive cavity and of the terminal 

 clubs of the tentacles, as well as the shape of the sensi- Fig. 304. 



tive bulbs ; according to McCi'ady, they are exceedingly 

 pointed in D. strangulata, while the sensitive bulb of D. 

 conica widens as it approaches the circular tube. The 

 largest specimens taken were one sixth of an inch in 

 diameter ; smaller specimens, not more than an eighth 

 of an inch, differed greatly from the more advanced. 

 The bell is almost globular, of uniform thickness ; the 

 digestive cavity is short and rectangular in shape. As 

 the young advance in age, the spherosome becomes more 

 and more bell-shaped, and then conical ; as the digestive trunk increases 

 in length, it contracts near the base, and becomes pear-shaped towards 

 the extremity. When still quite young, the first appearance of the 

 constriction becomes visible ; larger and older specimens, measuring 

 one fourth of an inch, have a digestive cavity divided into two cavities, 

 Fig. 305. separated by a constriction, 



as in Fig. 304, where this 

 separation has become quite 

 prominent; when the Medu- 

 sa is in violent motion, the 

 proboscis will assume a qiiad- 

 rangular shape, with a large 

 four-sided opening ; this flex- 

 ibility of the actinostome is 

 lost in older sjjecimens. In 

 the oldest specimens which 

 have been found (Fig. 305), 

 the separation between the 

 upper and lower part of the digestive trunk has become such, that the 



Fig. 303. Tentacle of Dipurena conica. 



Fig. 304. Digestive cavity of a specimen in which the constriction has abeady separated the 

 upper and lower halves. 



Fig. 305. Adult Dipurena conica, in which the two digestive cavities are widely separated j 

 greatly magnified. 



