318 



MEDUSAE OF THE WORLD. 



Hydroid and young medusa.— The hydroid of this species has been obtained from the 

 egg by A. Agassiz, 1865. The egg develops into a pear-shaped planula which grows to be very 

 long and narrow before it becomes attached. The hydroid is very slender and the hydrothecae 

 are cup-shaped. The polypites are long and slender, and there are about 12 long, delicate 

 tentacles which are covered with prominent nematocyst-capsules. A web connects the ten- 

 tacles at their bases, but this may be an embryonic feature. At the end of 6 months the hydroid 

 formed small tufts barely perceptible to the naked eye. Medusae were not developed upon 

 these reared specimens. 



In the young medusa 35 mm. in diameter there are no traces of the gonads. The peduncle 

 is short and extends only about three-quarters the distance from the inner apex of the bell- 

 cavity to the velar opening. The 4 lips are by no means so large as in the adult. There are 16 



Fig. 177. — Tima lucullana, drawn by the author from 

 a specimen collected by Dr. Lobianco, 

 at Naples, Italy. A, side view of medusa, 

 natural size. B, part of bell-margin, litho- 

 cysts not shown. 



Fig. 178. — Young medusa of Tima formosa, after A. 

 Agassiz, in North American Acalephae. 



tentacles with well-developed basal bulbs, and according to A. Agassiz there are no lithocysts. 

 Fewkes, however, maintains that in this stage there are 2 lithocysts between each successive 

 pair of tentacles and that each lithocyst contains 7 concretions. 



This medusa appears in its mature form upon the New England coast in the early spring 

 months. It is common in Buzzard's Bay and Newport Harbor in April and May, but dis- 

 appears before the first of June. It has, however, been found north of Cape Cod, in Massa- 

 chusetts Bay in autumn and winter. 



According to Fewkes, 188 1, if the stomach of Tima be lost it is replaced in 4 or 5 days. 

 The formation of the new stomach begins simultaneously at 4 areas which are near the ter- 

 minations of the 4 radial tubes, and they increase in size and join at their sides, thus regen- 

 erating the stomach. 



