306 



HETEROCORDYLE 



I am indebted to Dr. dii Plessis, of Nice, for the specimens which have enabled me to 

 define the present species, and from which the accompaiiyinp- woodcut has lieen made. Tiiey were 



developed in his aquarium, where they spread them- 

 selves over the surface of sea-weeds, which were 

 obtained from the neighbouring shores at probably 

 a slight depth from the surface of the sea. They 

 afforded me the means of determining the real 

 nature of the hydrophyton in the genus Sfj/hcfix, 

 and to show that it is very different from that of 

 Podocoryne, in which the surface of the hydro- 

 rhizal expansion is covered by a stratum of abso- 

 lutely naked ccenosarc, a character which Fodocoryne 

 possesses in common with Hydractinia. The 

 hydrophyton of Sh/Iadis, on the other hand, while 

 it is almost entirely reduced, as in Hydractinia 

 and Podocoryne, to the condition of a hydrorhiza, 

 is formed, like most other hydrorhizse, on the 

 common type of a network of anastomosing 

 chitine-covered tubes. 



The hydranths of Slylactis ineniiis are sur- 

 rounded at their origin by a narrow cup-like pro- 

 cess of the hydrorhiza. They are very mutable in 

 shape, and run through a range of forms depending 

 on different states of contraction, similar to what we 

 meet with in Podocoryne and Hydractinia. The 

 tentacles, when in a semi-contracted state, assume 

 a somewhat club-shaped form. The sporosacs, which are clustered round the body of the 

 hvdrantli, at a little distance l)elow the tentacles, varied from two to six in num])er. The more 

 mature sporosacs were filled with ova at the time of examination. 



A, a colony of the natural size, spreading over a piece of 



sea-weed. 



B, portion of a colony magnified, a, hydranth, from which 



no gono])hores are developed (sterile hydrantli), ex- 

 tended ; h, same contracted ; c, gonophore-hearing (or 

 proliferous) hydranth. 



