358 



THE INHABITANTS OF THE SKA. 



similar to the huge Chrysaora, from one of whose ova the 

 primitive hydratube was produced. 



Tn a similar manner the Coryniadas, a family of hydrozoic 



Various forms of Corymadae. 



a and b. Vorticlava huwilis. c. Four polypites of Hydractinia echinatn, growing on a piece of shell. 

 d. Portion of Syncoryne Sarsii, with medutriform zooids (g), budding from between the ten- 

 tacles (t) of the polypite (o).- (All, except a, magnified.) 



polyps, which, unpossessed of the firm investment ofthesertula- 

 rians, are frequently found decking sea-weeds and stones with 

 dense arborescent structures, give birth to detached medusi- 

 form zooids. On the other hand, many medusid forms produce 

 organisms directly resembling their parents, and many fixed 

 Hydrozoa, such as the Sertularidae, do not give birth to free- 

 swimming medusoids, but to ciliated gemmules, which, escaping 

 from the capsules in which they had been formed, soon evolve 

 themselves into true polyps. A great part of this " strange 

 eventful history " is still enveloped in darkness, as the life of 

 comparatively but few Hydrozoa has been thoroughly in- 

 vestigated ; so . much is certain that future observations will 

 bring many ,new interesting relationships to light, and add new 

 links to the chain which'binds together the various members of 

 the hydrozoic class. 



Although the Ctenophora, thus named from the ciliated bands 

 which constitute so obvious a feature in their physiognomy, closely 

 resemble the Medusae by their gelatinous consistence and their 

 mode of life, yet a more complex organisation assigns them the 



