SOME EFFECTS OF EXTERNAL CONDITIONS UPON 
THE WHITE MOUSE 
BY 
FRANCIS B. SUMNER 
Witn Fourteen Ficures 
The production of definite modifications in the structure, color 
or size of animals or plants by artificial changes in the conditions 
of life has been successfully accomplished over and over again by a 
large number of investigators. I need only allude to such classi- 
cal instances as the experiments of Dorfmeister, Weismann and 
others on butterflies, Schmankewitsch on Artemia, Cunningham 
on flounders, Naegeli and Bonnier on Alpine plants, or to the 
more recent work of Tower' upon beetles and Beebe? upon birds. 
The fact that such considerable modifications may be produced 
within the lifetime of an individual by physical or chemical means 
is in itself interesting if regarded simply as an illustration of the 
plasticity displayed by many organisms. But when we push our 
inquiry beyond the merely descriptive plane, we are brought face 
to face with some of the most fundamental problems of biology. 
Are these modifications adaptive in their character? Do they in 
any instance correspond to the features which distinguish one 
natural species or geographical variety from one another? And 
finally, do such artificially produced modifications reappear in 
offspring which have not themselves been subjected to the con- 
ditions of the experiment? These are some of the questions 
which demand an answer from the investigator. They are not so 
simple and easy of solution as may appear on the surface: the first 
1An Investigation of Evolution in Chrysomelid Beetles of the Genus Leptinotarsa. Carnegie 
Institution, 1906, pp. 320, pl. 30. 
* Geographic Variations in Birds, with Special Reference to the Effects of Humidity. Zodlogica: 
N. Y. Zool. Soc., Sept. 25, 1907, pp. 41, pl. 6. 
