HYDROZOA. 89 



Transitional forms of this kind should not, however, 

 surprise us, when we consider the common bond, 

 community of descent, which, connects the two 

 kinds of appendages in question. 



In the genera Perigonmius, Atractylls, Pen- 

 naria, Gorymorpha,Acaulis, Stauridia, and some 

 forms of Goryne, Tubularia, and Eudendrium, 

 the gonophores assume the aspect of free-swimming 

 medusoids. In most other Corynidce they are 

 fixed, exhibiting many remarkable gradations of 

 structure. An intermediate condition is presented 

 by the curious reproductive zooids of Clavatella, 

 which, though locomotive, scarcely merit the ap- 

 pellation of medusiform. They are described by 

 Mr. Hincks as free polypoid buds, furnished with 

 six forked processes, set round the margin of a 

 central hemispherical disc, one limb of each fork 

 being capitate, like the tentacles of the polypite 

 itself, the other terminating in a peculiar sucker- 

 like enlargement. By means of these organs the 

 zooid, when detached, moves freely about, until 

 finally it proceeds to mature its generative pro- 

 ducts. 



The gonophores of Trichydra, Vorticlava, and 

 La7' have hitherto remained unknown. 



Two families of Corynidce have been distin- 

 guished, though the character employed to sepa- 

 rate them appears to be somewhat artificial. 



Order CORYNID.E. 



Family i. Coetniad^. 



Polypary absent, or rudimentary. 



Family 2. TuBULARiADiE. 



Polyjoary well developed. 



