250 



THE HYDRA 



Fig. 121. — Cellular structure of hydra. 



A, longitudinal section. B, cnidoblast with discharged nematocyst (cf. Figs. 123, 124 

 and 125). C, nematocyst as in B before discharge. D, nematocyst of another type before 

 discharge, b, b', bud; e, enteron; ec, ectoderm; en, endoderm; /, foot; g.c.en., gland cell 

 of endoderm; g.c.f., gland cell of foot; hy, hypostome; l.en.c, large endoderm cell; mo, 

 mouth; n.c.ec, nerve cell of ectoderm; n.c.en., nerve cell of endoderm; n.c.t., nerve cell 

 of tentacle; ne, nematocyst; n-s.c, neuro-sensory cell; s.c, endodermal gland cell of 

 hypostome; s.c.ec, sensory cell of ectoderm; s.c.en., sensory cell of endoderm; s.c.f., sensory 

 cell of foot; s.c.l., sensory cell of tentacle; s.l., supporting lamella; i, tentacle. 



