I82 



ZOOLOGY 



absorption. Pseudopodia are formed, and particles are directly 

 taken into the body of the cell. Special gland cells also occur in 

 the entoderm, by the secretions of which the food undergoes 

 changes preparatory to absorption. There is no anal opening. 

 Undigested remnants are eliminated at the mouth. Respira- 



FlG. 83. 



-nu. 



Fig. 83. Nettling cells of Hydra (after Schmeil). A, unexploded; B, exploded, b, barbs; c, 

 the nettling cell in which the nettling organ is developed; en., the cnidocil or "trigger;" cf., the 

 capsule or nettling organ; /, the nettling filament or lasso; n, neck of the capsule; nu., nucleus of 

 the cell. 



Questions on the figure. — Compare the parts of the nettling organ before and 

 after explosion and note the difEerence in position. How would the barbs in the 

 neck of the capsule behave as it is forced inside out by the compression of the 

 capsule? Find from reference literature the nature of the fluid secreted on the 

 inside of the lasso. 



