CHAPTER IV 



THE HYDROMEDUSAE.^ 



CLASS HYDROMEDUSAE. 



Order 1. Anthomedusae. 

 „ 2. Leptomedusae. 

 ,, 3. Trachomedusae. 

 „ 4. Narcomedusae. 

 ,, 5. Hydrocorallinae. 

 „ 6. Siphonophora. 

 Sub-Order 1. Disconectae. 



„ 2. Calyconectae. 



„ 3. Physonectae. 



„ 4. Auronectae, 



„ 5. Cystonectae. 



The organisms which are dealt with in this chapter and the next 

 under the class-names Hydromedusae and Scyphomedusae were, 

 until quite lately, regarded as being so much more closely allied to 

 each other than to any other class of the animal kingdom that they 

 were grouped together under the name Hydrozoa (a name due 

 originally to Huxley), in contrast to the other great division of 

 Coelentera, the Anthozoa. It has, however, become increasingly 

 probable that, near akin as are Scyphomedusae to Hydromedusae, 

 their race-history indicates a yet closer relationship to Anthozoa ; 

 the term Hydrozoa has therefore been dropped altogether for the 

 purposes of the present work, although the further step of uniting 

 Scyphomedusae and Anthozoa under the class-name Scyphozoa (as 

 some suggest) has not been taken. 



Definition. — Hydromedusae are Coelentera, Avhich typically 

 present two main forms of individuals — the non-sexual hydroid and 

 the sexual medusoid (gonophore) ; in this case the life -history 

 exhibits an alternation of generations, in which the hydroid pro- 

 duces the medusoid by lateral budding, and the fertilised eggs of the 



1 By G. Herbert Fowler, B.A., Ph.D. 



