IV 



PHYLUM CCELENTERATA 



147 



But the simplest members of the whole class, with the exception 

 of one or two imperfectly known forms which will be referred to 





cnc 



_! TMS _ 



100 mm 



SCALE FOR A 



FIG. 107! Hydra. A, vertical section of entire animal ; B, portion of transverse section, highly 

 magnified ; C, two large ectoderm cells ; D, endoderm cell of H. viridis ; E, large uematocyst ; 

 F, small nematocyst ; G, sperm, a, ingested diatom ; bd. 1, bd. 2, buds ; chr. chromatophores ; 

 cnbl. cnidoblast ; cnc. cnidocil ; ect. ectoderm ; end. endoderm ; ent. cav. enteric cavity ; ent. 

 cav'. its prolongation into the tentacles ; fl. flagellum ; liyp. hypostome or manubrium ; int. c. 

 interstitial cells ; m. pr. muscle-processes ; mth. mouth : msgl. mesogloaa ; ntc. large, and ntc'. 

 small nematocysts ; nu. nucleus ; ov. ovum ; ovy. ovary ; pad. pseudopods ; *py. spermary ; 

 vac. vacuole. (From Parker's Elementary Biology, after Lankester and Howes.) 



below, are the Fresh-water Polypes of the genus Hydra. The 

 entire organism (Figs. 27 and 107) consists of a simple cylindrical 



L 2 



