Royal Physical Society. 227 



naked, and is evidently not aware of the existence of a poly- 

 pary or common connecting base between them. A similar 

 ignorance of the existence of a polypary and corallum in 

 Clava is also betrayed by Van der Hoeven in his " Handbook 

 of Zoology." If the descriptions given by these writers were 

 correct, Clava would stand alone among all the marine hy- 

 droidse as a naked and single polyp. One species only of 

 this zoophyte has been hitherto described, under the names 

 of Clava parasitica (Gmelin), Hydra multicor nis (Forskal), 

 Coryne squamata (Miiller), and Clava multicornis (Johnston). 



2. In a note on Dioecious Reproduction in Zoophytes, con- 

 tained in the " Edinburgh New Philosophical Journal," vol. 

 iv. p. 313,* I mentioned that I had noticed two species of 

 Clava, and that the polyps were not separate, as hitherto de- 

 scribed, but were attached together by a fleshy basis, invest- 

 ing a horny polypidom, somewhat similar to that of Hydrac- 

 tinia, or by a creeping thread inclosed in a membranous 

 sheath. In the same month of July, I found a third species 

 at South Queensferry, when examining the shore there with my 

 friend Mr Murray. These three species I propose to designate 

 by the names of Clava cornea, Clava repens, and Clava 

 membranacea. 



3. Clava repens (Plate XI., fig. 1) occurs plentifully on the 

 friable sandstone of the Scougall rocks near Tantallon Castle. 

 Its polyps are joined together by a polypary or ccenosarc, a 

 fleshy fibre inclosed in a thin tubular corallum, which creeps 

 along, and adheres to the stone. This polypary is readily 

 overlooked, as the "colletoderm" or glutinous envelope of its 

 corallum is generally coated with the detritus of the rock and 

 other foreign matters. The polyps have therefore the appear- 

 ance of being solitary, and ranged in irregular lines, as shown 

 n Van Beneden's drawing.f These polyps are about five or 

 six lines in length, white, or coloured with tints of rose or 

 flesh colour, and they sometimes exceed the polypary greatly 

 in thickness. About a half line of their attached extremity 

 is covered by a very delicate extension of the brown corallum 

 which remains as a cup when the polyp is removed by long 



* Ante, p. 165. f Recherches sur l'Embryogenie des Tubulaires, 1844. 



