PLATE III. 



Class CCELENTEBATA. 



HYDROZOA. 

 THE FRESH-WATER POLYPE (Hydra). 



FIG. 1. HYDRA (H. viridis) : BUDDING, x 10. 



t. tube : /. foot : m. mouth : tn. tentacles : b. bud. 



FIG. 2. HYDRA (H. viridis) : REPRODUCING BY SEXUAL PROCESS, x 10. 

 o. ovary : t. testes : c. oral cone, with the mouth at its apex. 



FIG. 3. TRANSVERSE SECTION THROUGH THE TUBE OR BODY, x V- 

 ee. ectoderm : en. endoderm : c. " body-cavity." 



FIG. 4. TRANSVERSE SECTION THROUGH THE TUBE, AND NEARLY LONGITUDINAL 

 SECTION THROUGH A TENTACLE, x V - 



t 1 . tube: t 2 . tentacle. 



FIG. 5. LONGITUDINAL SECTION THROUGH THE TUBE, x 6 f . 



ec. ectoderm cells with n. nuclei: n. 1 -, n. 2 nematocysts: m. support- 

 ing lamella : i. interstitial cells : en. endoderm cells with n. 

 nuclei, v. vacuoles, and /. food vacuoles : c. cilia. 



FIG. 6. ECTODERM CELLS ISOLATED, x 300. 



n. nucleus: p. 1 , p. 2 neuro-muscular processes. 



FIG. 7. NEMATOCYSTS : BEFORE AND AFTER EVERSION OF THE THREAD, x 700. 



