4 6 



THE HYDROMEDUSAE 



KEPRODUCTION. The asexual reproduction of this group is 

 apparently of the usual laminar type : medusoids, nectophores, 



FIG. 49. 



FIG. 51. 



49. Diagram of Physulia (modified from Cuvier and Haeckel). 



50. Upper surface of Velella, showing pneumatophore and sail (after Cuvier). 



51. Cormidium of Physalia, with a gonodendron (modified from Haeckel). 



D, dactylozooid ; G, gastrozooid ; GP, gonopalpon or dactylozooid on the gonodendron ; 

 M ?, female medusoid, ultimately freed ; M <J , male sporosac ; PN, pneumatophore ; T, tentacle 

 (palpacle) of dactylozooid or palpon. 



and (sometimes) hydrophyllia are formed after the manner sketched 

 on p. 20. The development of the fertilised ovum is known only 



