46 HYDROZOA. 



ridce and SertularidcE, while all three find acces- 

 sible representatives in the order Corynidce, 

 In certain species of this last order the gono- 



vph> f 



same in 



) 



modes of attachment. Thus in Glava multicornw 

 some are inserted on the polypites, others on gono- 

 blastidia ; while in Hydractinia, besides the gono. 

 phores borne on the gonoblastidia, a few are found 

 to arise, without intervening support, from the 



sides of the coenosarc. 



The gonoblastidia are either simple or branched. 

 Often they present a curious resemblance to true 

 polypites, from which, however, they differ in 

 wanting a mouth, and having usually shorter ten- 

 tacula. Such polypoid gonoblastidia may be ex- 

 amined with ease in Hydractinia, where they are 

 less than the polypites in size. In this genus the 

 free extremity of each is seen to end in a pear- 

 shaped, tapering enlargement, whose surface is 

 studded with minute conical swellings containing 

 thread-cells, which increase in size so as to re- 

 semble rude tentacles, ten or twelve in number, 

 around the largest portion of the pyriform pro- 

 cess. Beneath these the gonophores are borne. 

 At the base of the process is inserted a proble- 

 matical body, presenting the appearance of a short 

 stalk, which terminates distally in a rounded ex- 

 pansion, filled with very small, dark orange, masses 

 of 'pigment. < . 



In general, gonoblastidia arise from the sides o 

 the coenosarc, though, in some cases, they are 

 attached to the bodies of the polypites. 



A curious structural modification distinguishes 



the erono blastidia of the Sertularidce. In @ arfl ' 

























