FAMILY CARES — NURSERY DUTIES. 151 



tbeir eggs in holes, and these eggs are white 

 also. 



Now, it is quite probable that there is no desire 

 and no need to build in holes either because the 

 plumage is brilliant or the egg is white. Why 

 these particular birds nest in dark places has no 

 place in the present connection, we have simply 

 to offer an explanation of why, whenever this 

 occurs, the egg is white. Very probably it is 

 for the purpose of rendering the egg visible; 

 otherwise it would stand in hourly danger of 

 being crushed by the parent every time it 

 entered the nest, or , lost if laid in caves or 

 spacious cavities. 



Our British puffin seems to furnish us with a 

 concrete example of the truth of this hypothesis. 

 At one time, like its relations the auks and 

 guillemots and razor-bills, it laid richly coloured 

 eggs in the open ; later it has resorted to 

 burrows, and now covers its eggs with a wash 

 of white, sometimes so thinly that the pattern 

 can be plainly seen shining through, sometimes 

 the pattern is almost entirely concealed. We 

 take it that the bird has had to whiten its eggs 

 in order to see them in so dimly-lighted a place 

 as a burrow. Birds lay white eggs hecatise they 

 lay in burrows, and not vice versa. For a some- 

 what similar reason plants that are fertilized by 

 night-feeding insects have white flowers, white 

 being conspicuous in the dark whilst colour is 

 invisible. 



We ourselves adopt a similar expedient. Thus 

 in the dark corridors of the Natural History 

 Museum a piece of white paper is pasted around 



