362 NEMOPSIS GIBBESII. 



Nemopsis Gibbesii, H'Crady. 



Nemopsis Gibbesii, — i)f'Cr«f/y, Gymnoplitlial. of Charleston Harbour, p. IGO, pi. x, figs. 1 — 7. 



TROPHOSOME. — Htdeanths having the form of an elongated cone ; tentacles 

 about ten (?) in the proximal circlet, and six (?)' in the distal ; those of the proximal 

 circlet in two closely approximate alternating serieso 



GONOSOME. — MEDUSA-buds on short, simple peduncles, which are scattered 

 irregularly over the space between the proximal and distal sets of tentacles, Plaxo- 

 BLAST, at time of liberation, with three or four tentacles in each marginal cluster, 

 and with its manubrium destitute of oral tentacles. Mature medusa with its vertical 

 shghtly exceeding its transverse diameter ; sixteen filiform and two clavate tentacles 

 in each marginal cluster ; oral tentacles very much branched, springing from a point 

 at some distance above the mouth ; generative lobes extending from the manubrium 

 along the radiating canals for about two thirds of the length of the canal. 



Development of Gonosome. — Winter. 



HaUtat of detached (?) hydrantb. — Free, floating at large in the open sea. 



LoeaJify. — Charleston Harbour, M'Crady. 



Our sole knowledge of the hydroid just descril)ed is derived from the observations of 

 M'Crady, no other naturalist having yet met with it. It is full of interest, even though we may 

 be permitted to doubt the normal freedom of the complete trophosome. " The appearance of the 

 medusa,'' says M'Crady, "is at once singular and beautiful. The conspicuous crescentic outline 

 of the pale orange-coloured sexual ribbons, the vivacioxis movements of the mouth and its 

 appendages, the graceful waving outline of the flapping disc, with the clavate tentacula carried 

 erect, as if always on the watch, the others floating in xarious curves, or lightly curled at their 

 extremities, make it an unusually remarkable object even in this remarkable group." 



The ocelli of the two clavate marginal tentacles of the medusa are, according to M'Crady, 

 " carried on their lower surface turned somewhat inwards, that is, towards each other ; the 

 ocelli of the other tentacles on their inner surface." 



M'Crady believes that he has been able to follow the development of the medusa from an 

 early condition as a bud still attached to the trophosome to that state in which the generative 

 lobes have attained their complete form ; and his observations have been repeated and in many 

 respects confirmed by A. Agassiz in planoblasts captured at large in the open sea. He has 



^ M'Crady makes no mention of the number of tentacles; the numbers here given are such as 

 appear to be indicated by his figures. 



