112 Mr. A. H. Hassall on Marine Zoophytes. 



that species, which is probably nothing more than the common 

 branched condition, not worthy of being considered as a variety, of 

 Antennularia antennina, contains no reference to the two chief specific 

 characters of my species, viz. the circumstance of the polypidom 

 arising by a single trunk, and the absence of the small tubular pro- 

 cesses placed between the proper polype-bearing cells present in A. 

 antennina. I propose, therefore, to designate my species Antennu- 

 laria arborescens, a term which expresses one of its peculiarities. 



Alcyonidium glomeratum. Polypidom massive, of no very defined 

 outline ; colour a deep uniform red, the shade of which approaches 

 to vermilion. 



I have lately been informed by Dr. Johnston that the Alcyonidium 

 rubrum of M filler is very different from the deep red Alcyonidium 

 referred to by me in the seventh vol. of the ' Annals of Natural His- 

 tory,' and which I supposed to be identical with that zoophyte. 

 Although not the Alcyonidium rubrum of Midler, I still regard it 

 as specifically distinct, notwithstanding the observations of Mr. 

 Macgillivray to the contrary ; or at all events, if it does not claim to 

 be regarded as a distinct species, it can only be looked upon as a 

 permanent variety, which is the next thing to a distinct species. 



Mr. Macgillivray aj>pears inclined to consider it as a mere acci- 

 dental variety, and observes that I appear " to regard it as distinct, 

 apparently on the sole ground of not having been able to detect any 

 gradations of colour between it and the common kind, as might be 

 expected were it a mere variety;" and says further, " that to be con- 

 sistent, I ought to separate as so many distinct species those Sertu- 

 laria which are occasionally found of a bright pink colour, and make 

 two species out of Laomedea geniculata, of which Dr. Johnston has 

 often observed coloured and colourless specimens growing upon the 

 same stone." 



The cases do not appear to me, however, to be at all analogous : 

 the polypidoms of the Hydroid zoophytes are corneous and extra- 

 vascular, while those of the Alcyonidia are coriaceous, fleshy, and 

 continuous with the polypi themselves ; the colour in Alcyonidium 

 glomeratum is, therefore, probably a secretion from glands placed in 

 it, which cannot be the case with the Sertularice. Moreover the 

 colouring matter is uniformly diffused over the surface of the polypi- 

 dom of A. glomeratum-, while in the Hydroid zoophytes it usually 

 extends only over a portion of the polypidoms, parts of them retain- 

 ing their normal appearance. 



Believing that in doubtful cases the truth is more likely to be eli- 

 cited by separating species than by uniting them, I have ventured 

 to assign a distinct specific name to what some would be disposed 

 perhaps to regard as a mere variety; an opinion, however, in which 

 at present I by no means concur. 



Farcimia spathulosa. Internodes three or four times as large as' 

 those of Farcimia salicornia ; cells spathulate, that is to say, rounded 

 above and excavated below, for the reception of the head of the ceil 

 beneath ; apertures semilunar, situated in the upper third of each 

 cell. 



