10 BRITISH HYDROID ZOOPHYTES. 



tube or casing composed of a horny substance 

 called Chitine. This casing forms a somewhat 

 loose jacket, and clothes in the more simple 

 forms (ATHECATA) only those stem-like and 

 branching portions (Coenosarc) of the animal 

 structure. In a few exceptional cases the 

 skeleton is of carbonate of lime. These little 

 horny branching growths are frequently cast 

 upon the beach in tangled masses with 

 seaweed and other objects. On examination 

 with a lens, it will be generally found that the 

 tubes are empty, the animal part having 

 become decomposed. The entire horny 

 envelope of the colony is called the 

 polypary. 



Polypite receptacles. In the higher 

 forms of hydroids (THECAPHORA) this covering 

 is more fully developed, and is expanded 

 so as to form receptacles for the polypites 

 themselves. These receptacles take the 

 form of chalices or elegant cups, often with 

 deeply scalloped margins and ringed stems. 

 Those with the ornamented margins bear a 

 close resemblance to the delicate little flower, 

 the Hare-bell, and they have consequently been 

 named " Campanulariidae." 



