WATER RELATIONS IN HIBERNATION. 247 



dominant, but its behavior in a Mendelian way is no indication 

 of its origin after its production. 



NATURE OF THE ALTERATION. 



As already shown, the alteration in the Tucson cultures is 

 physiological, involving a specific aspect of the reproductive 

 cycle, that of the resting period which is passed in hibernation, 

 and the only sure test of its existence is that of the survival 

 under the conditions of the northern winter, at the place of 

 origin of the stocks. This fact limits the possibilities of testing 

 and experiments with the modifications that are possible, since 

 no certain structural alterations in correlation with this change 

 are demonstrated up to the present, and the differences in the 

 color in the materials are too insecure criteria to be used at 

 present. 



What the physical or chemical changes are there is no indica- 

 tion at the present time, and one interpretation has about the 

 same chances of being the correct one as any other excepting 

 for the fact that the modified materials show a difficulty or slow- 

 ness in water loss which seems to me to suggest more probably 

 some altered condition in the colloids. 



The chief question that concerns us in the consideration of 

 the nature of the alteration, is whether it is an added or new 

 condition, or the revival of an ancestral one. 



The species L. decem-lineata, originally confined to the eastern 

 slopes of the Rocky Mountain uplift, and eastward over the 

 Great Plains into western Kansas and Nebraska, from whence it 

 gradually spread eastward to the Atlantic coast, has as its 

 nearest relatives, a series of species that are confined to the high 

 plateaus of Mexico; areas of semi-desert with arid conditions, 

 especially in the resting season. Using the usual criteria of 

 kinship, similarity in structures and habits, the species L. multi- 

 tceniata and oblongata are the nearest relations of this northern 

 species phylogenetically. 



All three species interbreed rather freely, are in developmental 

 sequences similar, as in their ecological relations, in their repro- 

 ductive cycles, in relation to the growing season of the habitat 

 in which they live. These relations and conditions I have 



