128 ELEMENTARY ZOOLOGY. 



6. To Light. Eyes, and general light sensitive- 

 ness; certain pigments. 



7. To the Medium. The skin and its special out- 

 growths; sense of touch, taste, smell; organs 

 of locomotion. 



B. Adaptations to the special conditions of life. 

 I. Primarily inorganic relations. 

 II. Primarily organic relations (i. e., adjustments 

 to other organisms) . 



1 . To animals of the same species. 



a. Friendly and social. 



Mating adaptations ; parental care of young ; 

 organic colonies; social and communal life. 



b. Competitive. 



Struggle among members of the same spe- 

 cies for food, mates, etc. 



2. To animals of different species. 



a. Friendly and social. 

 Commensalism ; symbiosis. 



b. Competitive. 



The predaceous habit; adaptations for 

 offense and defense; parasitism. 



141. Special Adaptations to the Inorganic Environment. 



The great adjustments which all organisms must make 

 to the non-living surroundings are suggested under "A" 

 above. Under the present heading would come all the 

 special degrees and variations of the qualities which give 

 such variety and richness to animal life everywhere. 



The adjustment to light is fundamental; but animals 

 are very different in the way and degree to which they 

 use it. Some animals love light and others shun it al- 



