360 



GENERAL PRIN'CIPLES 



prepares it for absorption and assimilation by digestion. Such 

 an animal is said to be holozoic. 



745. Some times two organisms of dilYerent kinds are found 

 living together by mutual consent, apparently, and partake of 

 the same food. The sea anemone, on the shell of the hermit 



B 



¥iG. 226. — Seasonal dimorphism in a European butterfl}^, Araschnia levana. 

 Both are females: A, the winter form; B, the summer form. X2. 



crab, is often quoted as an example of this kind. The anemone 

 secures fragments of the crab's food, and the crab secures some 

 measure of protection by the presence of the anemone. Such a 

 relationship is called commensalism. More frequently the 

 needs of two organisms are to some extent complementary, and 

 one household may serve both to mutual advantage. This is 



