CCELENTERATA. 61 
Polypary.—The term “ polypary” or “polypidom” is applied 
to the horny or chitinous outer covering or envelope with which 
many of the Hydrozoa are furnished. These terms have also 
been not uncommonly employed to designate the very similar 
structures produced by the much more highly organised sea- 
mats and their allies (Polyzoa) but it is better to restrict their 
use entirely to the Hydrozoa. 
