Chap. IX. 



TABULAR VIEAV. 



36^ 



Ph. Arethusa Til.-^ Ag., PI. 35. — Ph. aurigera McCr.— Gnlf of 

 Mexico (Brown, Sloane); Charleston, South Carolina (McCrady). 

 7th Sub-order. PIIYSOPHOR^, G^o/c^.^ — PhosophoridtB Esch. (p. p.). 

 1st Faoiily. PETHOSOMEiE Less. (p. p.). — Hippopodidoe Kdll. 



Gleba Forsk., Otto. — Hippopodius Q. and G. — Protomedea DeBl. — 

 Stephanomia Q. and G. — Elephantopus Less. 

 Gl. Hippopus Forslc.;'' LeucJc, Arch. Nat, 1854, PI. 12, figs. 1-5.— 

 Hippopodius lutens Q. and G., Ann. Sc. Nat, Vol. X. PI. 4, 

 Zool. Astr., PI. 2, figs. 13-21; Vogt, PI. 13. — H. neapohtanus 

 Koll., PI. G, figs. 1-5. — Mediterranean (Forskfd). 

 Vogtia Koll. 



V. pentacantha Koll, PI. 8. — Messina (Kolliker). 

 2d Family. Physophorid^ Esch. (restricted), Huxl. — Physophoras Less. — 

 Discolabaj Less. — Angela; Less.1 

 Physophora Forsk.* — Cupulita Q. and G. 



Ph. hydrostatica ForsJc, PI. 33, fig. E ; Vogt, Pis. 3-6; Gcgenb. 

 Neue Beitr., Pi. 31. — Physophora Philippii Koll., PI. 5. — 3Iedi- 

 terranean (Forskfd). 



^ The species of this and the preceding sub-orders, 

 thus far described, are most fully enumerated by 

 Lesson ; but it i-emains to be seen which are truly 

 distinct. 



^ Instead of discarding altogether the species 

 described by Quoy and Gaimard, in the Zoology 

 of the Astrolabe, most of \vhich are figured from 

 imperfect specimens, I have here attempted to 

 classify them according to the method so success- 

 fully applied in the study of fossil remains, com- 

 paring the parts preserved and illustrated by the 

 French zoologists, with corresponding parts of the 

 European species, now fully known by the extensive 

 researches of Milne-Edwards, Kolliker, Leuckart, 

 Vogt, Gegenbaur, and Huxley. From the obser- 

 vations of these naturalists, it is now evident that 

 all the representatives of this sub-order arise, like 

 Physalia, from a primary hydra. But there is 

 this essential difference between the Physalia; and 

 the Physophorse, that in the first, the primary 

 hydra produces no secondary sterile meduste, and 

 that the fertile medusas arise from secondary hydra; ; 

 while in PhysophoroB, the abactinal sides of the 

 primary hydra produce more or less numerous 



sterile meduste, and the fertile medusie arise directly 

 from the primary hydra. Again, the primar}' 

 hydra of the Physophora; is reduced to the func- 

 tion of an axis, around which the two kinds of second- 

 ary medusie and the secondary hydrie arise ; while 

 iu Physalias, the primary hydra remains the most 

 prominent individual of the community, even though 

 it is not the most highly organized. The Rhizoph}'- 

 sida; seem to be the only family in which there appear 

 no secondary sterile medusie. Whether Discolabe 

 Stephanospira has any or not remains doubtful. 



' While Kolliker, Leuckart, and Vogt's figures and 

 descriptions of this type agree fully with one another, 

 and with ForskSl's, those of Quoy and Gaimard's 

 differ so strikingly, that I am strongly inclined to 

 believe in the existence of two closely-allied genera 

 observed by different authors, and more or less 

 mixed up by Delle-Chiaje and Lesson ; but I have 

 no means of settling the difficulty. Leuckart has 

 at one time considered them as distinct, and after- 

 wards again identified them. 



■• The European species alone is satisfactorily de- 

 scribed ; those from other parts are very imperfectly 

 known. 



