EXERCISES. 453 



3. Degree of connection, organic or social, between the in- 

 dividuals of a species; gregarious, social and communal life; 

 resulting social qualities; degree of division of labor; poly- 

 morphism. 



4. Power of regenerating lost parts. 



5. Growth; rate, and ultimate size; longevity. Special 

 hindrances to growth. 



6. Relation to human welfare : use as food ; effects on crops 

 and domestic animals ; the production or dissemination of dis- 

 ease in man ; capability of domestication ; other qualities help- 

 ful or hurtful to human interests. Which phyla furnish spe- 

 cies susceptible of domestication? 



7. Diseases among animals other than man. 



8. Coloration : pigments, internal and external ; other modes 

 of producing color; location of the color; supposed uses. 



9. Principal methods of avoiding or surviving unfavorable 

 periods, as cold, drouth, and the like. 



10. Qualities of offense and defense. 



n. Protective resemblance and mimicry. Other passive 

 modes of protection. 



12. Parasitism and the degree of degeneracy resulting from 

 il. 



IV. Geographical Distribution. Select several representa- 

 tive species from each animal phylum and learn everything 

 you can concerning their distribution on the earth. Are they 

 local species or cosmopolitan species? What seems to be the 

 reason for the fact? Are all the phyla cosmopolitan? Com- 

 pare the phyla from the following points of view : 



1. The facilities for migration. The special modes of 

 migration, both active and passive. 



2. What are the principal barriers to migration and distri- 

 bution in the case of the representatives chosen for study? 



3. Find instances of species of animals apparently closely 

 related, with different geographical distribution. Compare, 

 for example, the species of hares and rabbits found in North 

 America ; the species of lynx ; of bears ; of the alligators ; spe- 

 cies of Unio; of the lobster; of the genus Equus. 



