302 STYLACTIS. 



Colour ofIIi/drmil/t.—yf\\\iQ. 

 Habitat. — On Flustra fuliacea. 

 Bathymdrical didntmtion . — Coralline zone. 

 Locality. — Ilfracombe, Rev. T. Hincks. 



Mr. Hincks informs us that the most striking character in the present species " is the series 

 of projecting bosses round the base of the tentacular ring. Wlien examined with the microscope 

 these are seen to consist of a number of elongate, bean-shaped thread-cells, which are piled 

 together so as to form silvery-white prominences on the lower side of the tentacles." He believes 

 that " they occur only on the alternate arms," where they " form a unique garniture.'' 



The species was dredged from a depth of ten fathoms, where it occurrred exclusively on 

 Flustra folia cea . 



STYLACTIS, AUniau. 



Name. — From aruAoc, a column, and uKric, a ray. 

 PouocoRYNE, — Sars. 



TROPHOSOME. — IIydiiocaulus not developed. Htdkouiiiza formed by a net- 

 work of anastomosing- stolons invested with a chitinous peeisarc, but without a super- 

 ficial layer of naked ccenosabc. Htdbanths sub-claviform or cylindrical, with the 

 tentacles filiform, and arranged in a single circlet round the base of a conical hypostome. 



GONOSOME. — Sporosacs, borne on the hydranths at the proximal side of the 

 tentacles. 



I have fouiul it necessary to constitute the genus St^lactis for the reception of two hydroids 

 described by Sars, both of which he referred to the genus Fodocoryne, while one of them was 

 at first regarded by him as a mere form of Fodocoryne carnea, though he afterwards expressed 

 his belief in its specific distinctness fi'om that hydroid. 



They are both, however, distinct from Fodocoryne, for, independently of other differences, 

 the fact of their gonophores being in the form of simple sporosacs instead of medusae renders it 

 impossible to admit them into the medusa-bearing genus Fodocoryne. 



For an opportunity of examining living specimens of Stylactis I am indebted to Dr. Da 

 Plessis, of Nice, and in these I was enabled to satisfy myself that not only is the gonosome 

 different from that of Fodocoryne, but that the hydrophyton is constructed on a plan entirely 

 different from that of the hydrophyton of this genus, for it consists of a network of anastomosing 

 tubes, invested with a chitinous perisarc, and without any superficial covering of coenosarc, such 

 as we meet with in Fodocoryne and Ilydractinia. (See woodcut, fig. 79, p. 306.) 



