NOTES ON PLYMOUTH HYDROIDS. 153 



Plumularia alleni * n, sp. 



Habitat. Found growing on Antennularia ramosa. This delicate 

 species bears considerable general resemblance in size, form, and 

 parasitic habit to F. halecioides. It differs, however, in having a non- 

 fascicled stem, smaller hydrothecse, more numerous nematophores, and 

 especially in the gonangia, which are greatly unlike the annulated 

 structure of F. halecioides. 



Aglaophenia pluma, Linn. In studying the development of the 

 corbulffi of this species, an interesting fact regarding the sarcostyles 

 was noticed. A young corbula was under examination, the leaves or 

 ribs of which had not yet coalesced, and the sarcostyles of one leaf 

 were seen to stretch across and attach themselves to the next leaf in 

 front, and remain for some time in that position. It appeared as if 

 these sarcostyles served as temporary attachments to hold the edges of 

 the two leaves together, while they were connected by trabiculis of 

 coenosarc, which rapidly formed a stronger and permanent connection. 

 The perisarc of the edges of the leaves seemed exceedingly thin, and in 

 places appeared to be wanting. A contact having been established 

 between the edges of adjacent leaves, the permanent attachment was 

 soon formed, and the coelomic cavities of the leaves established con- 

 nections at these points. A little later, currents of water bearing 

 granules were seen to flow in active streams from one leaf to the other. 

 In their incipient stages it is difficult to tell the difference between 

 sarcostyles and gonophores, and they make their appearance at about 

 the same period in the development of the corbulse. 



Aglaophenia helleri, MarUanner- Turner etsclur.'^ This is the form 

 collected by Mr. Allen from Eddystone Eocks, and mentioned by 

 him on page 49, volume iv., No. 1 of this Journal. This being the 

 first record of A. helleri on British shores, the following description is 

 given for the benefit of those who may not have access to the original — 



Trophosome. Colony unbranched, attaining a height of three-quarters 

 of an inch. Stem monosiphonic, divided by very deep nodes into short 

 internodes, each bearing a hydrocladium springing from its antero- 

 lateral aspect. Hydrocladia alternate, closely-set, divided into inter- 

 nodes, each bearing a hydrotheca, and partly divided by two imperfect 

 transverse septa. Nodes very distinct. Hydrothecte obconic, about 

 as deep as the aperture is wide. Marginal teeth nine, unequal in size, 

 the anterior one often being slightly incurved, and rather longer and 

 more pointed than the others ; the second and fourth teeth, counting 



* Named in honour of the Director of the Plymouth Laboratory, an enthusiastic worker 

 in marine zoology. Detailed description with figures will be published in Ann. mid Mag. 

 Nat. Uist. 



t Die Hydroiden des K. K. Naturhistorischen Ho/imiseums, Vienna, 1890, p. 271, plate vii. 



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