BOWERBANKIA CAUDATxV. 521 



The cells are large and stout^ and somewhat squared 

 at the top^ during retraction. Through the transparent 

 walls the polypide, which exhibits the most highly 

 specialized form of the Ctenostomatous structure, can 

 be readily examined"^. It has ten tentacles, which are 

 not everted at the extremities, and form a rather slightly 

 expanded bell. They are furnished with numerous bristles, 

 ranged in a single line along the back. Joliet states that 

 in the case of the erect form he has frequently met with 

 only eight tentacles ; ten, however, seems to be the pre- 

 valent and normal number. 



In summer, when reproduction is proceeding, the colo- 

 nies are tinted red by the larvae which occupy the cells. 



Habitat. On various Fuci, Corallina officinalis, other 

 Polyzoa [Flustra, Vesicularia, &c.), on the underside of 

 stones, &c., from between tide-marks (chiefly) to deep 

 water (?). 



Localities. Very common and generally distributed. 



Geographical Distribution. White Sea, on Alcyoni- 

 dium (Mereschkowsky) : Caspian Sea (O. Grimm) : Os- 

 tend (Van Ben.) : Roscoff, on Fucus serratus and Fuco- 

 dium nodosum (chiefly), also on Cystoseira, in the Lami- 

 narian zone ; especially fine and abundant in brackish 

 water (Joliet) . 



Bowerbankia caudata, Hincks. 



Plate LXXV. figs. 7, 8. 

 Valkeria caudata, Hincks, Ann. N. H. ser. 4, xx. 215 (1877). 



Stem creeping. Zooecia elongate, subcylindrical, biserial, 

 opposite, truncate at the top, slightly narrowed below, 



* It is the subject of one of Dr. Farre's classical memoirs, which have con- 

 tributed so largely to our knowledge of the anatomy and physiology of the 

 Polyzoa. 



