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HYDROZOA 



79 



Section III, 



CLASSIFICATION OF HYDROZOA. 



I. Classification. — a. Order i : Hydridas. — 3. Order 2: Corynida? 

 ~t 0rde '\ 3 : Sertularidae. - 5. Order 4 : Calycophoridss. - 6. 

 Order 5 : Physophondaj. — 7. Order 6 : Medusidaj. — 8. Order 7 • 

 Lucernandae. ' ' 



I. Classification. — The seven orders into which 



follows : 



Hyd 



1 . Hydrides. — Hydrozoa, whose hydrosoma con- 

 sists of a single locomotive polypite, with 

 tentacles, hydrorhiza, and reproductive organs 

 which appear as simple processes of the body- 



wall. 



2. 



Corynidce. — Hyd 



whose hydrosoma is 



fixed by an hydrorhiza, and consists either of 

 one polypite, or of several connected by a 

 coenosarc, which usually developes a firm 

 outer layer. Eeproductive organs in the 

 form of gonophores, which 

 structure, and arise from 



polypites, from the coenosarc, or from gono- 

 blastidia. 



3. Sertularidoe. — Hyd 



much in 



vary 

 the sides of the 



„ 'ozoa, whose hydrosoma 

 fixed by an hydrorhiza, and consists of 

 several polypites, protected by hydrothecaB, 

 and connected by a coenosarc, which is usually 

 branched, and invested with a very firm outer 

 layer. Eeproductive organs as gonophores, 



arising from the coenosarc, or from gonoblas- 

 tidia. 



