DEFENSE OF YOUNG 437 



many insects, and the stinging cells of the corals, jelly- 

 fishes, and their numerous relatives. In several of the 

 fishes (for example, certain of the eels and rays) there are 

 electric organs sufficiently powerful in a large individual 

 to paralyze a man temporarily. The devil-fishes, squids, 

 and related species throw out an inky cloud when molested 

 and escape amid the» gloom. From such examples it is 

 but a short step to those cases where protection is afforded 

 to an animal covered with foreign substances, as de- 

 scribed in the section on Protective Resemblances. 



Defense of Young. — Adaptations used in the de- 

 fense of the young are in most instances the same as 

 those serving for self-defense. 



Self-Defense in Plants. — Many species of plants, 

 as well as numerous fishes, shrimps and other prolific 

 animals, persist by sheer force of numbers. If a grass 

 plant or so-called weed is destroyed by some enemy, 

 enough remain to maintain the race. In numerous other 

 species the presence of thorns on stem or leaf renders 

 them comparatively free from attack. This is especially 

 true of desert plants where, amid severe conditions, the 

 number of individuals is relatively small and adapta- 

 tions along the line of self-defense are of supreme impor- 

 tance. In the same or more favorable situations certain 

 other species are covered with stiff prickles, or with sting- 

 ing cells, as in the case of the nettle, or, as in the Jack-in- 

 the-pulpit, are packed with needle-like crystals which in- 

 sure them against the attacks of insects, snails, and other 

 animals. Several species, such as the oxalis, develop 

 acids in their tissues, while many others form unpleasant 

 and even poisonous substances which probably enable 

 such individuals to escape complete destruction. 



Adaptations for Rivalry. — Battles among the male 

 individuals of a species for the possession of a female 

 occur in practically every class of animals from the crabs 

 and insects to man. Furthermore, it probably is self- 

 evident that the organs adapted for defence are chiefly 



