CUCKOW 123 
those of the rightful owner may be necessary, for there can hardly 
be a doubt as to the truth of Dr. Baldamus’s theory (the only 
theory, by the way, he has put forth), as to the object of the 
assimilation being to render the Cuckow’s egg “less easily recog- 
nized by the foster-parents as a substituted one.” But in this place 
it is especially desirable to point out that there is not the slightest 
ground for imagining that the Cuckow, or any other bird, can 
voluntarily influence the colour of the egg she is about to lay. 
Over that she can have no control, but its destination she can 
determine. It is also impossible that a Cuckow having laid an egg, 
should look at it, and then decide from its appearance in what 
bird’s nest she should put it. That the colour of an egg-shell can 
be in some mysterious way affected by the action of external 
objects on the perceptive faculties of the mother is a notion too 
wild to be seriously entertained.! Consequently, only one explana- 
tion of the facts can here be suggested. Every one who has 
sufficiently studied the habits of animals will admit the tendency of 
some of those habits to become hereditary. That there is a 
reasonable probability of each Cuckow most commonly putting her 
eggs in the nest of the same species of bird, and of this habit being 
transmitted to her posterity, does not seem to be a very violent 
‘supposition. Without attributing any wonderful sagacity to her, 
it does not seem unlikely that the Cuckow which had once success- 
fully foisted her egg on a Reed-Wren or a Titlark should again 
seek for another Reed-Wren’s or another Titlark’s nest (as the case 
may be), when she had another egg to dispose of, and that she 
should continue her practice from one season to another. It stands 
on record (Zoologist, 1873, p. 3648) that a pair of Wagtails built 
their nest for eight or nine years running in almost exactly the 
same spot, and that in each of those years they fostered a young 
Cuckow, while many other cases of like kind, though not perhaps 
established on authority so good, are believed to have happened. 
Such a habit could hardly fail to become hereditary, so that the 
daughter of a Cuckow which always put her egg into a Reed-Wren’s, 
Titlark’s, or Wagtail’s nest would do as did her mother. Further- 
more it is unquestionable that, whatever variation there may be 
among the eggs laid by different individuals of the same species, 
there is a strong family likeness between the eggs laid by the same 
individual, even at the interval of many years, and it can hardly be 
questioned that the eggs of the daughter would more or less 
resemble those of her mother. Hence the supposition may be 
fairly regarded that the habit of laying a particular style of egg is 
also likely to become hereditary. Combining this supposition with 
that as to the Cuckow’s habit of using the nest of the same species 
1 The misconception of the unreasoning mind on all these points is almost 
incredible. 
