60 On the Production of Colour in Birds' Eggs. 



the sea birds, too, by fouling their eggs, no doubt materially 

 assist in preserving them. 



The English cuckoo commonly chooses the nests of larks 

 or of wagtails for its Qgg. When found in the nest of a lark, 

 especially of a tit-lark, the Qgg is very dark ; and when 

 found in that of a wagtail, much lighter. This looks like 

 proof positive of the effect of mental impression in producing 

 the colour of the Qgg. More rarely, the Qgg of the cuckoo is 

 found in other nests, such as that of the hedge sparrow. 

 It is most likely that in this case, the cuckoo had in the 

 course of nature laid its Qgg, and not being able to find an 

 appropriate nest near, was driven to make use of that 

 readiest to hand. For nothing could be more conspicuous 

 than the contrast between the colours of the eggs. Our 

 Victorian cuckoos are likewise eclectics. The pallid cuckoo 

 often plants its cream or flesh-coloured and spotted eggs in 

 the nests of honey-eaters, the eggs of which its own 

 thus resemble. The bronze cuckoo patronises the dome- 

 shaped nests of little birds, in which the Qgg will not be 

 seen, and into which it doubtless conveys its Qgg by means 

 of the bill, for the cuckoo is much too large a bird to obtain 

 entrance into the nest by the tiny opening which serves for 

 the rightful owners. The brush and the narrow-billed cuckoos 

 place their eggs in the nests of superb warblers and acanthizas, 

 and the eggs of both are white, with very fine dots. 



The subject it will be seen is as yet still entirely in the 

 domain of observation. Experiments are wanting. It is to 

 be hoped that they will be forthcoming. Opportunities 

 exist, notably in the case of the domestic birds, and of 

 birds which breed easily in confinement. But we must 

 not expect too much, to be able to produce extreme effects. 

 Mr. E. B. Poulton's interesting series of experiments on 

 the production of colour in the pup?e of certain British 

 Lepidoptera, show that the capacity for variation in each 

 species is (for a single generation) limited, and that the 

 variations tend in quite definite directions. It is probable, 

 however, that results of sufficient, and perhaps in some 

 cases of striking, interest are to be obtained by careful and 

 systematic experimentation. And the field is open. 



