1153 The Zoologist — April, 1868. 



Thai is the rule, which (like all other rules) will not be without 

 exceptions. 



But before we proceed to discuss and explain it, there is another 

 inquiry, which, if not fully answered, should at any rate be stated. 



The question then is, does the same hen cuckoo lay eggs of the same 

 colour and markings only ? and so is she limited to the vests of but 

 one species ? 



Or else, does the same individual lay eggs of different colour and 

 marking, according to the character of the eggs amongst which her 

 own will be intruded ? My friend H. Knnz (to whom I first com- 

 municated my observations on the difference of colour in the eggs of 

 the cuckoo, and who also made similar observations) pronounced his 

 opinion in favour of the latter view, and advanced the following hypo- 

 theses (Naum. i. 2, p. 51): — " The sight of the eggs lying in the nest has 

 such an influence on the hen which is just about to lay, that the egg 

 which is ready to be laid assumes the colour and markings of those 

 before her." Such an event is in itself by no means improbable. There 

 could be adduced for it reasons and 'analogies from Physiology. 

 First, in one of the oldest records of history, viz. in the Pentateuch* 

 there is a relation of ancient experience, that sudden, extraordinary 

 and particularly strong or lasting impressions upon the senses (par- 

 ticularly on the sense of sight) of the mother during the conception 



occur eggs entirely olive-green or olive-brown, which in colour resemhle the eggs of 

 the nightingale, where, however, the larger end is of a darker, the smaller of a some- 

 what lighter, colour, as is the case with many eggs of the birds of New Holland. 



7. C. auratus, Gin., lays egt;s of a shining white. Levaillant affirms that it lays 

 its eggs in the nesls of the smallest insect-eaters; and since he shot a hen bird which 

 had iis own egg in its mouth, and thereupon he drew the conclusions that the bird 

 introduces its eggs by means of its beak into nests which it cannot enter, it is right to 

 accept this ; and the clear shining while of the eggs supports this assumption, that it 

 prefers to entrust its eggs to those species which breed in holes. Perhaps even the 

 allied species (Indicator major and minor), which lay white eggs in holes of trees, 

 belong to its foster-parents. 



Whether therefore, finally (Journal f. Omithol. i. 2, p. 144), Cuculus glandarius, 

 since it does not personally incubate its own eggs, can no longer remain as a type of 

 Swainson's order Oxylophus, is of no importance to this question ; but it is of im- 

 portance that the eggs of this parasite, too (whether it be a genuine cuckoo or not), 

 are so wonderfully like the eggs of the foster-parents that one can scarcely distinguish 

 thein, in colouring and marking, from many small specimens of the crow's eggs at 

 least that is the case with my own specimen, which I received from Heir A. Brehm. 



* Genesis xxx. 37 and following verses. 



