Prof. Allman on the Hijdroid Zoophytes, 137 



XV. — Notes on the Hijdroid Zoophytes. By Prof. Allman. 

 I. Laomedea flexuosa, Hincks. 



In the polypes of Laomedea flexuosa, the ectoderm of the ten- 

 tacles is extended laterally between these organs for a distance 

 of about a fourth of their entire length from their origin, so as 

 to form a web-like membrane, similar to that already pointed 

 out by Mr. Alder in L. acuminata. 



This peculiarity in a very common zoophyte seems to have 

 been hitherto overlooked, though, in a morphological point of 

 view, it is a character of much importance. 



II. The extra-capsular medusiform sporosacs {^^ meconidia^') of 



Laomedea, and the determination of the species in which they 



they are found. 



In a communication on the Reproductive Organs of the 

 Hydroid Zoophytes, read last year before the Royal Society of 

 Edinburgh *, I referred to the extra-capsular medusiform sporo- 

 sacs, so well known from Loven's description of them in a zoo- 

 phyte which he names Campanularia [Laomedea) geniculata, and 

 expressed my opinion that Loven^s zoophyte was not truly Lao- 

 medea genicalata, but L, flexuosa of Hincks, a species to which 

 I referred similar bodies which I had myself examined. 



Mr. Alder, writing to me since then, suggests the possibility 

 of the species which gives rise to these sporosacs being neither 

 the one nor the other, but a distinct, though not yet discrimi- 

 nated, species. 



As we know that both L. geniculata and L. flexuosa give rise 

 also to a different kind of sexual bud, it will be at once seen 

 that this question has an important physiological significance 

 apart from its bearing upon simple descriptive diagnosis ; and 

 I therefore availed myself of the first opportunity to inquire 

 critically into the subject. The result has been a conviction 

 that Mr. Alder's doubts are well-founded. 



A few weeks since, I obtained upon the shores of Cramond 

 Island, in the Firth of Forth, a Laomedea^ growing on the 

 fronds of Fucu^ vesiculosus, and loaded with gonophores, most 

 of which carried upon their summits the peculiar bodies under 

 consideration. 



The only described species of Laomedea with which it is pos- 

 sible to confound the Cramond zoophyte are L. flexuosa, L. gc' 

 niculata, and L. dichotoma. From L. flexuosa, however, it dif- 

 fers in the more elongated form of the polype-cells, in the more 

 conical form of the gonophores, and in the absence of the web 



* Proc. Roy. Soc. Edinb. 1868. 



