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 



nte 



- SCALE FOR A 



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

 magnified ; C, two large ectoderm cells ; D, endoderm cell of //. viridis ; E, large nematocyst ; 

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

 cnbl. cnidoblast ; cnc. cnldocil ; ect. ectoderm ; end. endoderm ; ent. car. enteric cavity ; ent. 

 eav'. its prolongation into the tentacles ; fl. flagellum ; hyp. hypostome or manubrium ; int. c. 

 interstitial cells ; m. pr. muscle-processes ; mth. mouth : ttugl. mesogloea : nlc. large, and ntc\ 

 small nematocysts ; nu. nucleus : ov. ovunj ; ovy. ovary ; psd. pseudopods ; tpy. 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 



