INDIVIDUAL DIFFERENTIATION AND ADAPTATION. 133 



with similar powers of response and adaptation come to be 

 located in the same kinds of conditions. This results in faunas 

 more or less characteristic of all the important kinds of en- 

 vironments : as marine, brackish water, fresh water, terrestrial, 

 aerial, cavern faunas, etc. 



11. The origin of animal life was in the ocean, and from 

 these marine types it is believed that all other forms of animal 

 life have come, by gradual adaptation to their present mode 

 of life. 



12. The various climatic zones of the earth and the principal 

 geographical regions are characterized by distinct forms of 

 life. For example, the lake life of Africa differs from that of 

 North America, and similarly for all the various types of 

 fauna. An analysis of such facts and an explanation of them 

 belongs to the geographical distribution of animals. 



169. Topics for investigation, in field, laboratory and library: 



1. What constitutes individuality in animals? 



2. In what respects (enumerate) and to what degree have you ever 

 noticed variety in a given species? In the offspring of a pair of parents? 



3. Have you ever observed any changes in structure in animals which 

 could reasonably be attributed to change in environment? Give evidence. 



4. Does use or disuse produce changes in the organs of an individual? 

 Why? Give illustrations. 



5. Enumerate some facts of your own observation which illustrate 

 heredity. 



6. Cite observed instances of associations among animals of the same 

 species, and determine as well as you can from your observations what 

 ends are gained by the association. 



7. Make an effort to classify a series of objects, noting carefully your 

 basis of classification; that is, the characters which you select in separat- 

 ing and grouping the individuals. The teacher can make this a most in- 

 structive exercise. A few objects of considerable diversity may be chosen, 

 as sand, pebbles, shells, crystals, a plant, an animal, and the student may 

 be required to examine each as fully as he can, write out the characters 

 which he discovers as belonging to each, being sure that he uses a simple 

 and observed feature in each statement. On the basis of these recorded 

 observations let him compare and group the objects. Or take a large 

 number of relatively similar individuals and, without stopping to write 

 their characters, let the student place or distribute them in groups near 

 or remote from each other in proportion to their unlikenesses, allowing 

 intermediate forms to stand between. Afterward he may be caused to 

 determine and justify his classification and to see whether other classifi- 



