THEIR REPRODUCTION (EGGS) 303 



a covered nest, the parent having for a variety 

 of reasons changed its mode of nesting from 

 that usually adopted by the group to which it 

 belongs. In not a few of these cases it is by 

 no means unusual to find an egg quite devoid 

 of pigments as in the Grass Warbler, for ex- 

 ample and we can thus understand how in the 

 course of time such a type might come to pre- 

 vail, the tendency of the colour-producing glands 

 to become functionless through want of use or 

 demand. We must also bear in mind another 

 common fact in nature, namely, that many con- 

 trivances are retained long after their direct use 

 has ceased, because they may be in no way 

 injurious to the species. But these are questions 

 quite outside the scope of the present volume, 

 fascinating enough, but demanding more scien- 

 tific treatment than is here possible or desirable. 

 We ought, however, in bringing the present 

 section of our subject relating to the Reproduc- 

 tion of Birds to a close, to devote a few lines 

 to the protective colouration of many newly- 

 hatched chicks. In a great many cases the 

 chick that has been brought to maturity within 

 a shell decked with protective hues, walks into 

 the world clothed in a dress of similarly pro- 

 tective design, and, what is more remarkable, 



