250 RHIZOGETON FUSIFORMIS. 



EHIZOGETON. Agassiz. 



Name. — From 'pi^a, a root, and •ya'ra.i', a neighbour ; so called from the situation of the 

 sporosacs on the hydrorhiza. 



TROPHOSOME. — Hyduocaulus evanescent. Hydhouhiza a creeping tubular 

 stolon, invested by a delicate perisarc. Hydranths sessile on the hydrorbiza, 

 elongated, subcylindrical, carrying towards their distal extremity scattered filiform 

 tentacula. 



GONOSOME. — Sporosacs springing from the hydrorbiza. 



Rliizoyetoii is one of the new genera described by Agassiz in his ' Contributions.' It has 

 certain affinities witii Clava, from which it differs chiefly in its gonosome, for the gonophores arise 

 separately from the hydrorbiza, while in Clava they spring from the body of the hydranth. 



Only one species has been as yet described. 



*^* Ehizogeton fttsiformis, Agassiz. 



RaizoGETON i'usiFOR5iis, — Ac/assiz, Contr. Nat. Ilist., U.S. vol. iv, p. 224, pi. xxii, figs. 17 — 



23. Clark, Mind in Nature, p. 73, note, figs. 38, 39. 



TROPHOSOME. — Hydranths attaining a height of from one eighth to one quarter 

 of an inch, invested by a delicate filmy pellicle, tapering distally to a blunt point ; 

 tentacles about twelve in number, borne by nearly the whole of the distal half of the 

 hydranth. 



GONOSOME. — Gonophores oval, elevated on peduncles, which arise singly from 

 the hydrorbiza ; both peduncles and gonophores invested by a filmy perisarc. 



General Colour. — Orange. 



Development of Gonomme observed in INIay. 



Habitat. — In rock-pools between tide marks. 



Bathytiictrical dhtrihiition. — Litoral zone. 



Locality. — Massachusetts Bay, Professor Agassiz and Professor 11. J. Clarke. 



