348 



HYDROID^. 



Part IV. 



4th Sub-order. SERTULARI^.^ Alternate generations or direct development." 

 Hydra always pedunculated and attached, protected by a 

 horny sheath, forming a distinct cup around the head. Me- 

 dusa either free or sessile, mostly flat, sometimes, however, 

 deep bell-shaped, with numerous tentacles, not more prominent 

 in the prolongation of the radiating chymiferous tubes, than 

 in the intervals between them, along the circular tube ; ^ Avith 

 or without independent eyes and marginal cirrhi. Eepro- 

 ductive organs always along the radiating chymiferous tubes, 

 and never ujDon the proboscis. 

 1st Family. AoLAURiDiE A(/. See note 2, p. 352. 



Aglaura Per. and LeS., Esch., DeBL, Less., Gegenh. (non Oken). 



A. hemistoma Per. and LeH. — Aglaura Peronii Leuclc. Arch. Nat., 

 1856, PI. 1, fig. 5; Gegenh., PI. 8, fig. ^. — Nice (Peron and 

 LeSueur); Messina (Gegenbaur).* 

 Lessonia Ei/d. et Soul. 



L. radiata Egd. et Soul, Bonite, Zooph., PI. 2, fig. 16. — South Sea 

 (Eydoux et Souleyet). 

 2d Family. Circeid.e Forties. See note 2, p. 352. 



Circe Mert., in Brandt's paper, Mem. Ac. St. Petersb., 1838. 



C. camtschatica Br., PI. 1. — Coast of Kamtschatka (Mertens). 



level of the circular tube. About eiglity rudimen- 

 tary tentacles between the two large ones. Sphero- 

 some of a light blue color; folds of actinostome, 

 dirty yellow ; tentacles, light brown. Height, three 

 quarters of an inch. — Gulf of Georgia, Was/dngton 

 Territory (A. Agassiz). 



^ This sub-order corresponds to the groups of 

 Hydroids generally designated under the names of 

 Sertularians and Campanularians, but, since many 

 of them are now known to produce free Medusse, 

 it is evident that all the naked-eyed Medusa; which 

 have the same structure as these, must be asso- 

 ciated with them, even though the origin of a 

 'majority of them remains at present unknown. 



'^ It remains doubtful whether some naked-eyed 

 MedusiB, such as the Trachyneraidre Gegenh., which 

 are known to undergo a direct development from 

 eggs, should remain in this sub-order. But when 

 I consider the difi'erence in the development of 



Pelagia and Cyanea, notwithstanding their close 

 affinity, I am inclined to believe that a regular 

 succession of generations, without the interposition 

 of an hydroid form, is no objection to the asso- 

 ciation of these naked-eyed Medusa^ with those, the 

 eggs of which produce Hydra? from which free 

 Medusfe arise. 



' When young, some of these Medusse have 

 four tentacles, and for some time, while s'till growing, 

 the tentacles in tlie prolongation of the chymiferous 

 tubes are larger than those placed in the intervals ; 

 but in course of time this difference gradually 

 vanishes. 



< The Aglaura penicillata BeBl., PI. 33, fig. 4. 

 belongs to the genus Polyorchis ; it is figured 

 twice, and appears under two different names in the 

 Manuel d'Actinologic. It is the Melicertum peni- 

 cillatum Escli., and is also figured under that name 

 by DeBlainville on PI. 38. See Polyorchis, p. 349. 



