i897-] BrownK. — The Hydroids of Valencia Harbour. 243 



sheath upon the base of the hydranth, and the sporosacs are developed 

 among the tentacles from the body of the hydranth. In the compact 

 form of this species the extension of the perisarc to the base of the 

 hydranth is not always visible, owing to its thinness and its closeness to 

 the ectoderm of the hydranth. But the existence of this extension 

 may be easily demonstrated by placing a part of the colony in dilute 

 potash for a short time, and then removing the hydranth. To the naked 

 eye these two forms appear to be distinct species, especially when the 

 extremes of each kind are compared. The presence of the gonophores 

 in the axils of the tentacles and the extension of the perisarc to the base 

 of the hydranth show that they belong to the same species The 

 difference in the form of the colonies is probably due to their situation, as 

 the compact colonies are usually found growing on sea-weeds, and the 

 long colonies attached to stones or the sides of rock-pools. May, 1895. 



Eudendrlum ramosum (Linn.) 

 A small colony, about i^ inches in length, with male gonophores, was 

 dredged in the harbour. August, 1896. 



Hydractlnla echlnata (Fleming). 

 Fairly common in the harbour growing on shells inhabited by hermit 

 crabs. 



Myrlothela phrygia (Fabricius.) 

 Fairly abundant on Church Island, and near Murreagh Point. It lives 

 near low-water mark, attached to stones. 



Rhlzogreton fusiform Is (Agassiz). 



The genus Rhizogeton possesses only one species — R. fusiformis — which 

 has hitherto only been found in Massachusetts Bay, U.S.A. 



During our visit to Valencia Harbour in April, 1895, Mr. Beaumont 

 found several colonies of this Hydroid living on the under side of stones, 

 near low-water" mark, on the shore near Knightstown. The Valencia 

 specimens do not agree in every detail with the species described by 

 Agassiz, as the following description shows ; — 



The trophosomes and the gonosomes are situated at irregular intervals 

 upon a creeping stolon which is closely and irregularly branched. The 

 lower half of the hydranth is covered by a perisarc which at the base is 

 conspicuous by its being covered with brownish particles, forming a 

 kind of collar about half a millimetre in width, and the upper portion of 

 the perisarc is clear, very thin, and difficult to see. The hydranth is 

 about 2-3 mm. in length and about \ mm. in width. 



It carries about 20 long tentacles which are situated upon its distal 

 half. The gonosome, like the trophosome, is also situated upon the stolon. 

 It is 1-2 mm. in length and completely covered by a very thin and 

 delicate perisarc. The gonophore is oval in shape, and is situated upon 

 a peduncle so that the gonosome appears club-shaped. In mature 

 specimens the ova were seen free inside the gonophore. The general 

 colour of the colony is pinkish. All the colonies were situated upon a. 

 dead polyzoon ( ? Metnbranipora) which had encrusted the stones. 



