300 WRIGHTIA ARENOSA. 



Wkightia akekosa, Alder. 



Atractylis ARENOSA, — Aider, Suppl. Catal., p. 7, pi. x, figs. 5 — 7. Wriyht, Quart. 

 Journ. Mic. Sci., vol. iii, New Series, pi. iv, figs. 7^ — 10. 

 Hincks, Brit. Zoopli., p. 88, pi. xvi, fig. 1. 



TROPHOSOME. — Hydrocaulus minute, simple, irregular in form, and with 

 dilated trumpet-shaped summit, attaining a height of about one line, invested with 

 particles of sand, mud, or other foreign matter. Htdranths with about twelve long, 

 slender, muricated tentacles, alternately elevated and depressed in extension ; the entire 

 hydranth retractile within the dilated summit of the trumpet-shaped hydrocaulus. 



GONOSOME. — Sporosacs (female') oval, very large in proportion to the size of the 

 hydroid. 



Colour of Hj/dranfhs.—M\W white ; Wright. 

 Development of Gonosome. — September ; Wright. 

 Habitat. — On the under side of stones and the roots of Laminaria. 



Localities. — Tynemoutli and Cullercoats, Coast of Northumberland, Mr. Alder; Largo, 

 Firth of Forth, Dr. Strethill Wright ; Coast of Yorkshire, Mr. Hincks. 



This remarkable little hydroid was first descril)ed by Mr. Alder, who, however, was 

 unacquainted with its gonosome. He referred it to the genus Atradj/lis of Wright. It was 

 subsequently found in its fully developed state by Dr. Strethill Wright, who was thus enabled to 

 study the structure and development of the gonosome, and who, as has been mentioned in the 

 former part of the present Monograph (see p. 49), has shown that the ova, after escaping from 

 the sporosac, became enveloped in a gelatinous mass, which continues adherent to the ruptured 

 sac. In this mass they undergo further development, and are ultimately liberated from it as 

 planulae. 



Mr. Hincks infoi-ms us that it is very common under stones and on Laminaria roots at 

 Filey Brig, Yorkshire. 



^ The male gonophores have not been observed. 



