II 



CN ID ARIA 



6' 



Order 1. Hydridae Fresh-water polyps . 



Single individuals or small stocks without envelopes consisting of a few similar 

 individuals. Reproduction asexual by gemination, and sexual. Hydra develop direct 

 from the egg. Hermaphrodite. Hydra, in fresh water. 



Order 2. Hydromedusse. 



Hydroid colonies, which are at least dimorphic, since, besides the sterile nutritive 

 polyps, there arise by gemmation sexual persons, which either detach themselves as 

 Cmspct?ufc. M'.dasce and swim about freely, or remain united with the colony as 

 medusoid gonophores. In one series of Hydromedusce the attached Hydroid form is 



FIG. ti-1 Bougainvillea ramosa (after Allman), with budding Meduss. li, Nutritive polyps; 

 mk, Medusa buds ; m, detached young Medusa (Maryclis ramosa). 



suppressed, as the Cmspedotc Medusa develops direct from the fertilised egg into 

 another Medusa. The systematic relationship of single forms is naturally determined 

 both by the Hydroid and by the Medusa forms. As the whole life-history and 

 development of only a minority of the many species is available, and in many species 

 only the Hydroid form is known, in others only the Medusa form, a natural system 

 of the Hydromedusce is still a desideratum. 



Hydroid form. Medusa form. 



Sub-Order 1. Hydrocorallia, 



Hydroid stocks, with calcined peri- "\Vanting. 



derm skeleton. The sexual products are 

 produced in gonophores. Stylasti r, 



