﻿Dec, 1856.] 



ELLIOTT SOCIETY. 



85 



Our wonder at this mode of development is enhanced when we 

 compare it with that of Turris neglecta as observed by Gosse. 

 The genus Turris is at most not distantly allied to Turritopsis, and 

 indeed so close are its structural affinities that throughout my 

 notes, to within a very short time, I uniformly ranke-d this Turri- 

 topsis in that genus. Certainly the two genera, as well as Oceania 

 and Saphenia, structurally considered, belong to one family. Yet 

 Gosse has shown that the ova of Turris fall as planules, attach 

 themselves and develope hydrse like those of other Naked-eyed Me- 

 dusae, undergoing, in all probability, a genuine specialized meta- 

 morphosis, or alternate generation. While our neighboring genus 

 Turritopsis, which is perhaps even more closely allied to Oceania, 

 undergoes a direct and regular metamorphosis in which the hydra 

 form never becomes attached. I have been tempted at times to 

 think that perhaps these two modes of development might exist in 

 the same genus, but if thatdescribedhad existed in Turris or Oceania, 

 it is hardly possible that it should have escaped observation so long. 

 In the species of our own harbor a great many specimens occur 

 with larvae in the cavity of the bell, and these are so conspicuous 

 as even to be observable with the naked eye, and there is not the 

 least probability that an observer of even ordinary carefulness 

 should have overlooked them. On the other hand, I have never 

 seen anything which could even have led me to the suspicion that 

 Turritopsis had any other mode of development. It seems, then, 

 that if these two modes of development do not occur in the same 

 species and genus they at least occur in the same family. 



The generic affinities of Turritopsis, with Oceania, are still more 

 striking, and I am yet in considerable doubt as to whether they 

 are not one and the same. Yet the descriptions of European 

 species seems to render it probable that there are two groups in the 

 genus — one characterized by long, and comparatively few, tenta- 

 ■cula, with ocelli on the outer side, and with the peduncle or pro- 

 boscis containing only the opaque sexual organs and digestive 

 cavit}'', while in the other (sub-genus Turritopsis) the tentacula are 

 very numerous, comparatively short, bearing their ocelli on the 

 inner side, while the upper part of the peduncle is formed by a 

 mass of large clear cells surrounding the origin of the chymiferous 

 tubes. To this sub-genus, I think, is referable the O. pusilla 

 of Gosse. If, in addition to the characters noticed above, the mode 

 of embryological development I have just described should be 



