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 

 gi^ound 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 

 indi\ddual, 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 



^ The misconception of the unreasoning mind on all these points is almost 

 incredible. 



