COLOUR IN BIRDS’ EGGS. 249 
the eggs of (say) a blue-egged Guillemot are affected by mating 
with one that comes of (say) a brown-egged family. 
At any rate Mr. Lucas says (p. 209), “ Individuals at the 
present day are influenced in part by the surroundings, but 
mainly restricted by the tribal habits of generations.” So the 
hypothesis in question assumes that the faculty of laying eggs of 
a given colour is hereditary, but capable of being varied to a 
certain extent in each case by the action of external objects on 
the brain of the parent bird. How are we to reconcile the 
extraordinary variety of colour in the eggs of this bird with the 
assumption that the colour is inherited by the race through many 
generations? Guillemots breed in large colonies. Surely in the 
course of generations, if the coloration of the eggs were 
determined mainly by a principle of heredity, the eggs in any 
given colony would gradually assume a more or less definite type, 
as in the case of other birds living together and interbreeding. 
It is evident that no one of the many varieties referred to is 
sufficiently superior to the others to have been “seized on” by 
Nature and transmitted by the principle of heredity. 
“ Mental receptivity,” as stated, may explain slight variations 
in eggs; but if applied to more marked variations, we must in 
these cases conclude that the effect of the surroundings on the 
individual bird is sufficiently strong to counteract any variations 
which Nature might have intended it to transmit ; in other words, 
a bird whose eggs at the present day are found to vary 
considerably is influenced not merely in part, but mainly, by its 
surroundings. 
We are to suppose that hen Guillemot No. 1, about twelve 
hours before laying each egg, is so much influenced by the colour 
of the sea that she lays a greenish or bluish egg; No. 2 is so 
affected by the appearance of sea-weed that her egg is covered 
with brown, green, or black markings, resembling sea-weed; and 
so on. And here again many questions naturally arise. For 
instance, what effect has the colour of the first egg laid, or rather 
the causes which produced that colour, on eggs subsequently 
laid? If none, how are we to support the assumption that 
each bird always lays similar eggs? Is her nature such that she 
is always impressed by the same objects ? 
When we come to birds which lay bright blue eggs, as the 
Hedgesparrow, it is impossible to believe that the colour is 
