PISCES. 371 



386. Supplementary Studies for Library and Field. 



1. What are the theories as to the origin of the paired fins of fishes? 



2. In what way do fishes change their long axis from the horizontal 

 position so as to ascend or descend obliquely in swimming? 



3. Range of size in fishes. 



4. Probable origin of fresh-water fishes. What forms are now able to 

 pass back and forth from fresh to salt water? 



5. Accumulate data concerning the habitat, food, breeding habits, dis- 

 tribution, economic importance (with the reasons therefore) of some of 

 the following fishes : salmon, trout, white-fish, sun-fish, muskalonge, her- 

 ring, eel, cod, flat-fish, mackerel, shark, ray, sturgeon, gar-pike, bowfin. 



6. What is known of the habits of the lung-fishes calculated to suggest 

 how the lung may be of value in preserving the life of the animals? 



7. Migrations among fishes. 



8. Parental care among fishes. 



9. The number of eggs produced by various species. 



10. Study figures showing the embryology of the salmon or other bony 

 fish. 



11. The blind fishes found in caves. What are the principal facts con- 

 cerning them, and what explanations have been offered to account for their 

 habits and modifications. 



12. Collect all the data possible concerning the flat-fishes. 



13. Examine all the figures of fishes found in your library, and make 

 note of the chief points of variation and the range of these. 



