NOTES ON THE SCIUBID.E. 243 



must be ver\' different. The tail as a balancer must be as much 

 required in summer as in winter, if not more so ; but, on the 

 other hand, the tail as a warm covering is not so necessary, and 

 hence probably the reason of its not being renewed. There is, 

 however, a further noticeable point about this tail, which is fully 

 dealt with by Mr. Thomas in the article quoted above, and that 

 is, that as it gets older it becomes lighter in colour, till by 

 autumn it is nearly white. Mr. Thomas further points out that 

 the red hairs of summer show no tendency to this bleaching 

 process, whilst the brown winter hairs slowly bleach throughout 

 the time they are worn, but, being replaced in spring, the process 

 is never so conspicuous on the body as on the tail, where the 

 change goes on throughout the year. 



Although we are accustomed to see fur and feathers of all 

 kinds " bleach " under the action of light, we are perhaps too 

 much inclined to take it for granted that the bleaching action on 

 a living animal goes on by the same process. This may be true 

 of a bird's feather, which is considered histologically dead, yet it 

 is hardly conceivable in a mammalian hair, which maintains 

 throughout its life an active connection with the body ; and, 

 bearing this in mind, one may notice that the bleaching, which, 

 if the tail were dead, one would expect to go on uniformly, starts at 

 the tip, and gradually spreads downwards towards its base, thereby, 

 to my mind, clearly showing that, although this lightening may, 

 and probably does, take place by a merely mechanical process, 

 yet such a process cannot act on the normal living hair. I may 

 be perhaps allowed to mention on this matter, that when bleaching 

 goes on among birds that bleaching process does not begin and 

 continue slowly throughout the life of any particular feather, but 

 a feather which may show hardly any change during the first six 

 months of its life will suddenly undergo considerable disintegra- 

 tion and bleaching on the seventh. Does it not seem as though 

 vital forces existed in that feather during the earlier part of its 

 life ? Taking our remarks on bleaching into a rather wider 

 field, we find that this "fading" is restricted either to certain 

 races, or to certain parts of the animals — for instance, among 

 the large and closely allied Squirrels of the Ratufa hicolor group, 

 as I have already shown in a previous paper,* which inhabit the 



'■'■'- Ann. and Mag. Nat. Hist. ser. vii. vol. v. p. 490 (1900). 



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