/. UYDBOZOA: HTDROCOBALLIN^^. 



2il 



regenerate the wliole animal. His experiments upon turning the animals 

 inside out have not been fully confirmed ; for in such cases the layers 

 resume their normal positions. Hydra grisea * (fusca), large browa 

 species ; H. viridis* green, from the presence of symbiotic algse. Fro- 

 tohydra ryderi* without tentacles. Polypodium hydrifornie, parasitic 

 on sturgeon eggs in Russia, needs more study. The marine Halereinita 

 eunudans may belong here. 



Order II. Hydrocorallinae. 



Exclusively marine, forming colonies of thousands of individuals whose 

 calcareous skeletons so closely resemble true corals that they were asso- 

 ciated with them until the animals were studied. MiUepora alcicornis,* 

 stag-horn coral, in Florida. The rosy Stylasters occur in tropical seas. 



Order III. Tubulariae = Anthomedusse (Gymnoblastea). 

 As a rule these colonial forms with perisaro but without hydrotheca 

 produce anthozoan medusie, but there are forms like Clava * (pink, on 



Fig. 1K5.— American Tubularian hrdroids. A. M ijr iothelia phryqiana (aftev Danielssen 

 and Koren); H. Sarsia josaiiti (after Fewkes); C, Monucaulispendula (after Agassiz); 

 II, Clava leptustyla; E, Furypha crucea ; F, Pviloioryne nurabilis (after Agassiz). 



rockweedj and Hydractinia * (on shells inliabiled by hermit crabs) 

 wliioh have sporosacs. Indeed the genera Corymorpha * and 3Iono- 

 caidis * are only differentiated by the existence of medusae in tlie former 

 and of sporosacs in the latter. In the forms with alternation of genera- 

 tions different names are applied to the hydroid and medusan stages as 

 follows : 



Hydroid. Medusa. 



Pennaria. Glohiceps. 



Synconjne. Sursia. 



Bougainvillea. Hipjiocrene, ilanjelis. 



Genunelaria. Geininarin. 



Podocoryne. Dijsiiwrphosa. 



