POLYl'l 19 



Province I.— RADIATA * 



Sub-Provmrr POLYPI. 



A polype is a small soft-bodied aquatic animal which 

 generally presents a cylindrical oval or oblong body, with 

 an aperture at one of its extremities surrounded by a crown 

 of radiating filaments or " tentacles." This aperture leads to 

 the digestive cavity, which, in most Polypes, is without intes- 

 tine or vent. A very large proportion of these animals has 

 organs of support, called " polyparies" or corals, of various 

 form and substance, but for the most part consisting of car- 

 bonate of lime ; and, as a general rule, locomotion is lost with 

 the development of the polypary, which usually attaches the 

 polype to some foreign body. The organization of the soft 

 tissues is in general simple ; the faculties of the Polypes are 

 very limited ; and the vital phenomena, save those of irrita- 

 bility and contractility, are inconspicuous. Nevertheless, the 

 influence of the combined powers of some of the species, in 

 adding to and modifying the crust of the earth, is neither 

 slight nor of limited extent. 



Class I.— HYDROZOA. 



Char. — Polypary, when present, flexible, external ; for the 

 most part developing cells for the polypes according to 

 regular patterns. 



Family I. — Graptoliiid^. 



To this class may probably belong the organic remains 

 called " Graptolites," which are exclusively and characteris- 

 tically Silurian fossils. A certain knowledge of their affinities 



* For the characteristic organization of the provinces, classes, orders, and 

 families of Invertehrata, reference may be made to the writer's " Lectures on 

 Invertebrata," 8vo, Longmans, 1855. 



