TRACHYNEMA DIGITALE. 59 



comes wrinkled between the chymiferous tubes ; the tentacles, when 

 contracted, become crimson at the extremity. 



The young Medusas are very different in shape from the adults. 

 Small specimens, measuring not quite an eighth of an inch in height 

 (Fig. 84), are quite globular; they have but few tentacles (Fig. 82), 

 the ovaries are not developed, the gelatinous proboscis is a mere knob 

 at the bottom of the bell, from which hangs down quite a long digestive 

 cavity. The abactinal part of the bell projects but slightly beyond the 

 general outline. It is in this stage that it resembles so closely the 

 Trachynema ciliatuin of Gegenbaur. When Fig. se. 



disturbed, they carry the lips of the actinos- 

 tome turned up, in a very characteristic 

 manner, as Gegenbaur has figured them. 

 In somewhat older specimens (Fig. 85) the 

 bell has become more elongated, the tenta- 

 cles more numerous, the ovaries make their 

 appearance as small pouches, as in Evicope, 

 and the gelatinous proboscis has extended 

 somewhat into the cavity of the bell. In 

 still older forms (Fig. 86) these parts have 

 all taken a more prominent development, 

 and we readily recognize, in the somewhat elongated bell, with the 

 large proboscis and slightly pendent ovaries, the future adult Trachy- 

 nema (Fig. 81), in which the develojDment of the gelatinous proboscis, 

 of the ovaries, of the tentacles, the lengthening of the bell, and its 

 increase in thickness at the abactinal extremity, have been carried 

 still further. The adult medusas attam a height of an inch or an inch 

 and a half 



I have identified this Medusa with the Medusa digitalis of Fabricius. 

 Forbes had, in his Naked-eyed Medusae, supposed a species of Turris to 

 be identical with it ; after a careful perusal of the description of Fa- 

 bricius, I am satisfied that it does not belong to the genus Turris, but 

 to Circe of Brandt, or Trachynema of Gegenbaur. Morch, in his List 

 of MedusEC of Greenland, retains the generic name of Forbes, and makes 

 it synonymous with Circe ; this is certainly a very different interpreta- 

 tion of the genus Turris of Lesson from what it has received thus far 

 by any writer on Acalephs. 



Baffin's Bay (Fabricius) ; Massachusetts Bay, Nahant (Alex. Agassiz). 



Cat. No. 376, Nahant, Mass., A. Agassiz. Medusae. 



Cat. No. 377, Nahant, Mass., A. Agassiz. Meduste. 



Cat. No. 449, Nahant, Mass., A. Agassiz. Medusas. 



Museum diagram Nos. 16, after Alex. Agassiz. 



Fig. 86. Young Trachynema, measuring over one third of an inch in height; the veil is 

 thrown out beyond tlie level of the circular tube. 



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