PROTECTIVE ACTIVITIES 



373 



suggests something even milder than a clam. But if you have 

 ever picked up a live jellyfish, you may have thought that a 



million needles had been 

 shot into your hand. The 

 skin of the jellyfish con- 

 tains a large number of 

 special cells in which 

 there are fine hollow 

 threads that shoot out 

 when the animal is dis- 

 turbed (see Fig. 190). 

 These " nettling cells " 

 are found in many spe- 

 cies of ccelenterates, such 

 as the hydra, sea anem- 

 one, coral polyps, and 



FIG. 193. Fighting ants ^ walnuts. 



But some animals, 

 like the ray, do give 

 their enemies a real 



electric shock when they are disturbed, and this is no doubt 

 of value in protecting them. The animal that has been 

 shocked quickly lets go and learns to let other shockers alone. 



Three forms of the Central American ant Chelio- 



myrmex nortoni : a, soldier ; b, medium worker ; 



c, small worker 



FIG. 194. The sting of the bee 



In this order of animals the weapon is the egg-laying organ. When the bee stings some- 

 one, the point is likely to remain in the flesh ; and as the animal flies away, some of its 

 internal organs are mutilated and the insect soon dies. The value of this weapon is not 

 so much for the protection of the individual as for that of the colony or species. The 

 individual is sacrificed to protect the group or to educate the enemies of the species 



Another way in which the organism can make itself disa- 

 greeable to an enemy, without really producing serious injury, 



