DIVISIONS OF THE HYDROZOA. 



67 



into a tubular cavity, which is everywhere excavated in the 

 substance of the ccenosarc (Fig. 17, b). The nutrient parti- 

 cles obtained by each polypite thus serve for the support of 



FIG. 17. a Seriularia (Diphasia) pinnata, natural size ; a' Fragment of the same en- 

 larged, carrying a male capsule (o\ and showing the hydrothecse (A); & Fragment of 

 Campanularia neglecta (after Hincks), showing the polypites contained in their hy- 

 drothecse (A), and also the point at which the ccenosarc communicates with the stomach 

 of the polypite (c). 



the entire colony, and are distributed throughout the entire 

 organism. The nutritive fluid prepared in the interior of each 

 polypite gains access through the above-mentioned aperture 

 to the cavity of the ccenosarc, which, by the combined exer- 

 tions of the whole assemblage of polypites, thus becomes 

 filled with a granular nutritive liquid. This coenosarcal fluid 

 is in constant movement, circulating through all parts of the 

 colony, and thus maintaining its vitality the cause of the 

 movement being probably due, in part, at any rate, to the 

 existence of vibrating cilia. 



The process of reproduction varies somewhat in different 

 members of the order. In all alike, however, the ordinary 

 polypites are incapable of producing the essential elements 

 of reproduction, and for this purpose special generative buds 

 have to be developed. In the typical Sertularians the re- 

 productive buds are developed at certain seasons in great 

 numbers, and they constitute what used to be called the 



