PLATE III. Fig. 4. An interstitial cell with its nucleus, granular cyto- 

 plasm, small mitochondria and a Golgi apparatus (G). 



Fig. 5. The line, indicating the magnification, passes through an appar- 

 ent cytoplasmic bridge between two adjacent interstitial cells. 



Fig. 6. The surface of Hydra showing the cuticular substance resting 

 on a membrane (Arrow # 1). Arrow # 2 shows another membrane, probably 

 the limiting membrane of the surface cells. 



12 



