382 



GENERAL BIOLOGY 



even on the back of the ox there are parallel phenom- 

 ena of distribution ; there are fly larvae that burrow beneath 

 the skin, there are ticks that cling to the surface, fleas that 

 run and jump about, and flies that take wing. 



Thus, the body of the large plant or animal becomes a unit 

 of environment for a host of dependent forms. Miniature 

 units are found in single organic products, such as the ear of 



Fig. 223. Young woodchuck {Arctomys monax) in the mouth of his burrow. 

 Photo by T. L. Hankinson. 



com, the head of cabbage, or any of the larger fleshy fruits; 

 how many inhabitants there are dwelling in each of these, 

 and how well they are localized and adjusted in place and 

 time, may be learned from the reports of our agricultural 

 experiment stations. The cone gall of the willow has a con- 

 siderable population, distributed in place as indicated in 

 figure 36, (page 46). In cases like these the distribution is 



