374 HETEROSTEPHANUS. 



fully extended contrasts with the relatively thick tapering stem of Vorticlava humilis ; and this, 

 with our present knowledge of Vorticlava proteus, wonld seem to be the only reliable character 

 for specific distinction. Under these circumstances it is with some hesitation that I retain the 

 Vorticlava jjroteus as an established species. Dr. Wright gives a series of figures showing his 

 hydroid in various states of contraction, and it woidd appear from these that the contractibility 

 and consequent mutability of form is possessed no less by the hydrocaulus than by the hydranth. 

 He informs us also that the hydroid "has the power of changing its place," a curious and 

 important observation. 



Wright has not been more fortunate in meeting with the gonosome of Vorticlava proteus 

 than Alder has been in meeting with that of Vorticlava humilis. 



HETEEOSTEPHANIJS, Allman. 



I^ame. — From 'InpoQ, dissimilar, and aTi(j,m'o<:, a wreath ; in allusion to the dissimilarity of 

 form between the two verticils of tentacles in the hydranth. 



TROPHOSOME. — Htduocaulus simple and solitary, destitute of peuisarc. 

 Htduanths with two verticils of tentacles, a proximal and a distal ; the tentacles 

 composing the proximal verticil filiform, those composing the distal verticil shorter 

 and capitate. 



GONOSOME. — Planoblasts borne on peduncles which arise between the two 

 tentacular verticils (?). Umbrella in the form of a shallow bell, with one large 

 marginal tentacle and three rudimental ones. 



The genus Heterosteplianus is constructed for the Corymorpha annulicor/iis of Sars, which is 

 certainly not a Cori/morpha, as, indeed, Sars himself suspects. It may possibly belong to the 

 genus Vorticlava, as already suggested by Hincks ; but, from our present knowledge of it, and 

 the absence of all knowledge of the gonosome in Vorticlava, we should not yet be justified in 

 associating the two forms in a common genus. I had originally assigned to this genus the name 

 of Heteractis ('Ann. Nat. Hist.' for May, 1864), overlooking the fact that Heteractis had been 

 already appropriated as a generic name by the botanist, but soon afterwards becoming aware of 

 the inadmissibility of this name, I changed it to that of Heterostephanus. 



