SYSTEMATIC 
ARRANGEMENT OF POLYPS. 
CLASS IL. 
POLYPI. 
ANIMALS contractile, having an intestinal cavity, with distinct 
terminal mouth, surrounded by tentacles or radiating lobes, seldom 
free, oftener affixed, aquatic; usually secreting a hard calcareous 
or horny body (polypary), and adhering to it. 
Propagation is by eggs, gems, stolons. Usually compound ani- 
mals are formed of many individuals cohering. 
Section I. Anthozoa EHRENB. 
Aperture of the nutrient canal single. Tentacles contractile, 
mostly without vibratile cilia. 
Orver I. Aydriformia. 
Tentacles of variable number. Nutrient canal excavated in the 
parenchyme of the body, not surrounded by an abdominal cavity. 
Family I. Hydrina. Naked, free, spontaneously affixed, with 
deciduous progeny. 
Hydra lu. Body cylindrical, narrowed into a pedicle, simple or 
ramose from the progeny not having been detached. Mouth 
crowned with tentacles, round, contractile, in a single whorl. 
Armed-Polyp: Sp. Hydra viridis, Tremp. Pl. 1. fig.; Rors. Zns. 111. 
Polyp. Tab. 88, 89. This green species was the first which TREMBLEY 
found ; it is rarer and smaller than the others.—H. Grisea, TREMB. 
Pl. 1. fig. 2 ;—H. fusca, Tree. Pl. 1. fig. 3, 4, polype & longs bras, 
