THE NATURALIST'S VISION 347 



with sex, or age, or season, can be recorded of the 

 commoner species of birds when kept in as nearly 

 natural condition as possible the year round. 



It is not so easy to observe changes of another 

 kind ; but I suppose most people realize that 

 birds as a whole, present in the tropics gayer 

 colors than in the more northern regions ; and 

 probably realize that the birds of the desert and 

 the birds of the region of perpetual snow have 

 taken on a general shade of coloring closely 

 assimilating with their environment. It does not 

 seem at all impossible, given artificial condi- 

 tions for producing an average temperature of 

 greater or less degree, together with a definite 

 amount of average humidity in the atmosphere, 

 as well as a measurable supply of light, that any 

 forms kept under such conditions might, and 

 probably would, after a number of generations, 

 show changes which we could conclude were 

 largely due to such a new environment as had 

 been artificially created. In short, it would not 

 be impossible in a laboratory to draw conclusions 

 and make observations as to what conditions pro- 

 duce certain results in color. 



In speaking to an eminent ornithologist in 

 England of the possibilities for observing birds 

 in confinement, and whether it were worth while 

 to go to the expense that would be thereby 

 entailed, he suggested to me that, if we could 



