130 A SCIENTIFIC APPRECIATION [ch. vi. 
widely different sides of natural science. But still 
higher rose my respect for his talents as I realised 
that he was no mere compiler, but that all he wrote 
showed that he had learned in practical study what 
he sought to teach.” 
His independence may be illustrated by a 
concrete case. It is well known that the stoat 
(Mustela erminea), which is brownish-red in summer, 
usually becomes white in winter, all but the black 
tip of the tail, and is known as the ermine. The 
prevalent view in MacGillivray’s day was that the 
brownish-red hairs lost their pigment and became 
white, a theory backed by the authority of Bell. 
But when MacGillivray, after his wont, looked 
into the matter for himself, he found the accepted 
account unsatisfactory:— 
“ In an individual obtained in December 1834, 
the colour was a mixture of white and brownish-red. 
The hairs of the latter colour were not in the least 
degree faded, and those of the former were much 
shorter, and evidently just shooting; so that the 
change from brown to white would seem to take 
place by the substitution of new white hairs for 
those of the summer dress.” 
This view has been confirmed by the very 
careful investigations' of Professor Schwalbe. 
Several instances of stoats of a brown colour 
patched with white, in which the white hairs were 
of the same length as the brown, led MacGillivray 
to think that “ sometimes the brown hairs them¬ 
selves, on the application of intense cold, become 
whitened ” ; and it is interesting again to notice that 
