CLAVA DIFFUSA. 247 



The species here described appears to be that which Forskiil had in view when describing 

 his Hydra mnllicortm, which is phiinly a different species from the Hydra squamata of Midler 

 and nmst be regarded as a scattered rather than a cUistered form of the genus Clava. 



The two forms, liowever, continued to be confounded by most subsequent writers. Joiuiston 

 describes them both under the name of Coryne squamata in tlie first edition of his ' Britisii 

 Zoophytes,' 1S38, and imder that of Clava mulficornis in the second edition, 1847, while his 

 figures, when they refer to a Clava at all, represent a scattered rather than a clustered form. 



The first, however, who described with sufficient fulness a scattered as distinguished from 

 a clustered species of Clava was Wright, who, under the name of Clava rcpms, described a 

 scattered species from the Firth of Forth. Not being aware of Wright's paper, the same species 

 was shortly afterwards described by myself under the name of Clava discreta. I now believe 

 that this species is identical with the Hydra multicornis of Forskal, and that it must therefore be 

 recorded under the specific name assigned to his hydroid by the Danish naturalist. 



Forskal's description is undoubtedly obscure, but I entirely agree with Mr. llincks's criticism 

 which leads him to refer the present species to the Hydra multicornis of Forskal. 



Clava midticornis is a much smaller and less conspicuous species than Clava squamata, from 

 which it is at once distinguished by its scattered habit, being never clustered like Clava squamata, 

 and by its filiform hydrorhiza, which never forms as in the last-named species a continuous 

 expansion by the lateral adhesion of its branches to one another. 



It attaches itself to stones much more frequently than is the case with Clava squamata, 

 which is almost always found on fuci or on timber piles between tide marks, and its bathynietrical 

 area is lower than that of this species. Its favorite resort is the under surface of detached 

 stones near low-water mark in situations but little exposed to the surf of the open sea. It would 

 thus seem to be a light-shunning animal — a habit in which it contrasts strongly with Clava 

 squamata. 



3. Clava diffusa, Allman. 

 Plate II, figs. 3, 4. 



Clava diffusa, — Allman, Ann. Nat. Hist, for January, 1863. 



TROPHOSOME. — Hydkocaulus rising to a height of ahout half a line from a 

 creeping filiform HrDBORiiiZA. Htduanths slender, from one quarter to half an inch 

 in height ; tentacles about twenty. 



GONOSOME. — GoNOPUOEES scattered singly and in small clusters upon the body 

 of the hydranth, along which they extend for some distance behind the proximal 

 tentacles. 



Colour of hydranth and gonophorcs, light rose-colour. 

 Development of Gonosome observed in July. 



