VARIABLE RESEMBLANCE IN VERTEBRATA, ETC. 95 



removing these white tips with a pair of scissors it 

 again appeared in its dark summer dress, but sHghtly 

 changed in colour, and precisely the same length as 

 before the experiment.' ^ 



This experiment conclusively proves, — (1) that 

 the external condition itself provides the cause which 

 brings the appropriate change in colour ; for the 

 animal did not change until subjected to the con- 

 dition ; 2 (2) that in all probability the cause is a 

 lowered temperature acting upon the skin ; (3) that 

 the existing dark hairs become white at the tips ; for 

 we cannot well believe that a fresh growth could have 

 overtopped the existing hair in a single night ; (4) that 

 the whitening hairs grow suddenly and rapidly. 



Nature of the change of colour in the American Hare 



The same conclusions are also supported by some 

 extremely careful observations conducted by F. H. 

 Welch upon the American Hare {Lepus Americanus) 

 in New Brunswick.^ In the latter district the animal 

 keeps its winter coat till May, when it is gradually 

 shed, the change being complete in June. The winter 

 coat gradually develops in October and November, and 



* Sir J. Ross : Appendix to Second Voyage, Nat. Hist. p. xiv. 

 1835. 



^ This conclusion is also supported by the fact that such changes 

 occur earlier when the winter is exceptionally early. Concerning 

 the Alpine Hare, see Tschudi, Thierlehen der Alpemvelt, p. 300. 



3 Proc. Zool. Sac. 1869, p. 228. 



