510 LOUIS AGASSIZ. 



tion. Whenever it can be done, and I hope 

 before long it may be done for all classes, it 

 will be desirable to take into account the rela- 

 tions of the living to the fossil species. Since 

 you are as fully satisfied as I am that the lo- 

 cation of animals, with all their peculiarities, 

 is not the result of physical influences, but 

 lies within the plans and intentions of the 

 Creator, it must be obvious that the succes- 

 sive introduction of all the diversity of forms 

 which have existed from the first appearance 

 of any given division of the animal kingdom 

 up to the present creation, must have refer- 

 ence to the location of those now in existence. 

 For instance, if it be true among mammalia 

 that the highest types, such as quadrumana, 

 are essentially tropical, may it not be that the 

 prevailing distribution of the inferior pachy- 

 derms within the same geographical limits is 

 owing to the circumstance that their type 

 was introduced upon earth during a warmer 

 period in the history of our globe, and that 

 their present location is in accordance with 

 that fact, rather than related to their degree 

 of organization ? The pentacrinites, the low- 

 est of the echinoderms, have only one living 

 representative in tropical America, where we 

 find at the same time the highest and largest 



