Albinistic Variations 
example, the appearance of red hackles in the 
cocks of black breeds of poultry. On the other 
hand, some certainly are not reversions, such as 
the appearance of a white ring in the neck of the 
female of the Rouen duck, which should resemble 
the Mallard as regards the plumage of the neck. 
Again, the tendency of Buff Orpingtons to 
assume white in the wings and tail must be 
regarded as a variation which is not in the nature 
of a reversion. In short, the efforts of all 
breeders are largely directed to fighting against 
the tendencies which animals display towards 
variation in certain directions. 
This tendency to vary in the direction of 
whiteness may account for many of the white 
markings which occur in nature, as, for example, 
the white tails of the Sea Eagle (Hakaetus 
albicella) the Nicobar Pigeon (Caloenas nico- 
barica), and many hornbills. Provided that such 
variations are not too great a handicap to their 
possessors in the struggle for existence, natural 
selection will allow them to persist. 
It was the belief of Linnzus, based on experi- 
ence, that every blue or red-coloured flower is 
likely to produce a white variety, hence he held 
that it is not safe to trust to colour for the identi- 
fication of a botanical species. 
‘On the other hand, white flowers are not likely 
to produce red varieties, and we believe we may 
positively assert that they never produce a blue 
E 65 
