142 ZOOLOGY 



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

 belongs to the geographical distribution of animals. 



13. Fossils are remains of former plant and animal life pre- 

 served in the rocks. We read much of the ancient life 

 history by a study of these fossils. We learn chiefly that life 

 started in a more lowly and more simple form than we now find 

 it; that it has been getting more complex and more like the 

 present with each passing age. What we find then at the present 

 moment on the earth is not the result of present forces. It is 

 the result of all the past. 



174. 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 

 variation 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 of the most striking facts of yoiar own observation which 

 illustrate heredity. 



6. Cite observed instances of groupings among animals of the same species, 

 and determine as well as you can from your observations what ends are gained by 

 the animals from 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 separating and grouping 

 the individuals. The teacher can make this a most instructive 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 classi- 

 fication and to see whether other classification could be made with a different basis. 

 Gasteropod shells, illustrating varieties of the same and different species; beetles; 

 butterflies; grass-hoppers; or even books of diverse shape, binding and contents 

 may be used. 



8. Can you suggest any cause for the loss of organs of parasites? Any 

 advantage? 



9. Cite instances from you own observation in which animals use the leap or 

 spring in capturing prey or escaping enemies. Why is it a peculiarly advantageous 

 adaptation? 



10. Cite instances of the food-storing instinct, with all observed details. What 

 is the most remarkable fact about them? How is it useful? 



