150 



TEXTBOOK OF ZOOLOGY 



TEMTACLE 



— MOUTH 



•TESTI S 



GASXRO- 

 VASCUl_AR 

 CAVI TY 



ECTODERM 

 MESOSLOE A 

 EfslDODERM 



OVARY 



BASAU DISC 



Fig. 71. — Diagrammatic longitudinal section of hydra, showing mature gonads and 

 typical cell layers. (Drawn by Titus C. Evans.) 



ECTODERM 



EPITHEl_IO- 

 MUSCUL. AR 

 CELL. 



I NJTER- 

 STI Tl Al_ 

 CEI_U 



NEMATOCYST 

 C N I DOBL. AST 



MESOGUOEA 



DIC3ESTIVE 



CEUUS 



G l_ A IM D 



CEI_U 



Fig. 72. — Cross-section through the column of hydra. The central space is the 

 gastrovascular cavity or enteron. (Drawn by Titus C. Evans.) 



