WATER RELATIONS IN HIBERNATION. 



249 



from hibernation is due to the same causes as it is in the tests 

 of the Tucson cultures. Unfortunately, I have no data con- 

 cerning the survival of the Mexican types at Chicago that are 

 at all comparable, so that I am not sure whether the pure Mexican 



TABLE X. 



* Chapultepec. 



t Cuernavaca. 



types are able to survive the Chicago winter or not, but it is 

 my opinion that they would not. 



The two Mexican species introduced into the deserts at 

 Tucson showed in the first introductions in 1908 a huge elimina- 

 tion during hibernation, but they survived in the following 

 year and continued a precarious existence for several years 

 thereafter. Later introductions survived, or failed, for reasons 

 not associated with the behavior in hibernation. 



Upon the basis of the probable phylogenetic relations, the 

 facts of the developmental cycles and the similarity in the 

 ecological relations and needs, the data in the crossing of the 

 species under the Chicago conditions and the survival values of 

 the FI found therein, and the obvious recessiveness of the northern 

 species in its hibernation behavior to the southern, gives the 

 basis for several conclusions of interest as to the nature of the 

 change. 



