112 HTDROZOA. 



rative appendages in many other forms, discharge, 

 in all probability, their proper functions, without 

 previous separation from the parent hydrosoma. 

 The gonophore either presents a well-developed 

 swimming-cup, with open margin and conspicuous 

 canals : or the calyx, with its canal system, may 

 remain in a very rudimentary condition, so as 

 scarcely to be distinguishable from its contained 

 manubrium ; while in the male organs of Stepha- 

 nomia and Athorybia the apex of the latter slightly 

 projects beyond the margin of the bell. In these 

 and many other genera each gynophore gives rise 

 to only a single ovum ; but there is reason to infer 

 that it may be otherwise with the free-swimming 

 gonophores of Physalia or Velella. 



Most of the Physophoridce hitherto examined 

 appear to be monoecious, the androphores and 

 gynophores being borne on the same gonoblastidia, 

 as in Physalia, Agalma, and Athorybia, or, more 

 rarely, on separate stalks, as in Stephanomia. 

 Besides the reproductive bodies, the gonoblastidia 

 may give support to hydrocysts and other appen- 

 dages, as in Physalia or Athorybia. In Halis- 

 temma they are absent or so extremely short, that 

 the gonophores seem attached directly to the 

 coenosarc. The phyogemmaria of Velella and Por- 

 pita are obviously homologous with the gonoblas- 

 tidia of Hydractinia or the small polypites of 

 Podocoryne ; and just as the former genera differ 

 from other Physophoridce, Physalia indeed ex- 

 cepted, in their laterally expanded coenosarc and 

 independent tentacles, so, likewise, may Hydrac- 

 tinia be distinguished from all the more typical 

 forms of Corynidcc, 



Of Physophoridoi Mr. Huxley has established 



