430 



ZOOLOGY. 



porpoises, etc., become more or less fish-like in form, in adapta- 

 tion to the medium. There is an enormous range in size in 

 the group, from the mice to elephants and whales. 



439. Supplementary Topics for Laboratory and Field Work. Com- 

 pare the relative size, length, etc., of head, neck, trunk and tail of various 

 types of mammals, using well known animals and the figures and de- 

 scriptions of less familiar ones. Can you find any signs of connection 

 between any of these facts and known habits of the animals studied? 



FIG. 230. Diagram of Skin in Mammals, by Folsom. 



Compare the anterior with the posterior appendages in a selected series 

 of mammals, keeping in mind the following points : size, length, strength, 

 uses ; the number and character of the digits. Compare similarly the 

 corresponding (i. e., anterior with anterior) appendages in another series. 

 Keep in mind, throughout, the adaptations of structure to the conditions of 

 life, method of locomotion, etc. 



