56 



HYDROZOA. 



been kept for some days in vessels of sea-water 

 it often happens that the polypites drop from their 

 stalks. Soon, however, new polypites are budded 

 forth, each having usually a smaller number of 

 tentacles than its predecessor. Similar are the 

 results produced by artificial fission. In this 

 manner, by section of a single stalk, Sir J. Gr. 

 Dalyell obtained, in the course of 550 days, twenty- 

 two successive polypites. 



SertularidjE. In most Corynidce, the course 

 of development closely corresponds with that above 



Fig. io. 



Development of Campanularia : —a, Campantdaria Lovem;t, 

 one of its gonoblastidia from whose summitproject two medusiform 

 gonophores, one of which is giving exit to a ciliated embryo ; c, 

 the same embryo, in its free swimming condition ; d and e, suc- 

 cessive stages of the young ccenosarc developed therefrom ; /, 

 medusiform zooid of Campanularia dichotoma ; — t, polypite ; *', 

 hydrotheca ; p', gonoblastidium. (a and / are about twice the 

 natural size; the others are much magnified.) 



described as taking pi ace in Cordylophom. Of a 

 similar character, in its more general features at 









