THE CCELENTERATES 



20I 



trate the skin of other animals (Fig. 120, B, C, D). The explo- 

 sion is probably due to internal pressure, and may be brought 



Fig. 120. — Parts of the body of hydra highly magnified. 



A, two cells containing muscle fibers ; B, two stinging cells or nemato- 

 cysts'; the lower one exploded ; C, part of a tentacle showing groups of nema- 

 tocysts; D, an insect larva shot full of nematocysts ; E, nematocysts coiled 

 around 'the spines on limb of a small animal; F, glandular cells from the 

 basal disk. (After various authors.) 



about by various methods, such as the application of a little 

 acetic acid or methyl green. Many animals when " shot " by 

 nematocysts are immediately paralyzed and sometimes killed 



