OBELIA FLABELLATA. 157 



hydrotheca is large, and both broad and deep. The rim 

 has usually been described as perfectly plain ; but on close 

 investigation it is found to be very slightly sinuated, and 

 the depressions answer to a number of sides or faces, which 

 give a polyhedral figure to the upper portion of the cup. 

 This structure can only be detected by careful examination 

 with the microscope. 



The differences between the gonozooids of the different 

 species of Obelia are very slight, at least in their earliest 

 stage. The multiplication of the tentacles is carried to a 

 great extent as the zooid advances towards maturity ; 

 Gegenbaur describes his Eucope pohjstyla, which he had 

 traced to a Campanularian stock, as possessing one hun- 

 dred and twenty of them. 



Hab. Common : often parasitical on other zoophytes. 



5. O. FLABELLATA, HillclvS. 



? SERTULARIA DICHOTOMA, Dalydl, Eem. An. Scotl. 212, pi. xli. 

 CAMPANULARIA FLABELLATA, Hincks, Ann. N. H. (3rd ser.) xviii. 297. 



Plate XXIX. 



STEM filiform, somewhat zigzag, branched, strongly annu- 

 lated above the origins of the branches, of a dark horn- 

 colour; branches alternate, flexuous, given off at each 

 bend of the stem, rather short and fan-shaped, divided 

 and subdivided dichotomously , and ringed above each 

 division, generally forked immediately above the point of 

 origin, the arms of the fork tending in opposite directions, 

 and giving a subverticillate appearance to the ramifica- 

 tion-, HYDROTHECA alternate, short and subtriangular, 

 with a wide aperture and an entire margin, borne on 

 ringed and tapering pedicels of variable length ; GONO- 

 THEC.E axillary, ovate, somewhat flattened at the top, 

 with a short tubular orifice, attached by a ringed stalk. 



GONOZOOID ? 



