278 THE STORY OF THE BIRDS 



wonderful variety. But here we must look 

 behind this beauty and variety, and seek their 

 motive and utility — the part they play in the 

 Story of the Birds. The study of nests and 

 eggs is one of the most important branches of 

 ornithology, for in the proper pursuit of it the 

 observer cannot fail to become familiar with 

 much of that detail which forms the all neces- 

 sary supplement to those portions of the science 

 which are covered by our earlier chapters. 



We may pass over the strictly embryological 

 portion of the study of Eggs, and com.mence 

 our description at that point in their history 

 when they receive their shell in the uterine 

 chamber of the parent. Here, according to Dr. 

 Gadow and other anatomists, the egg remains 

 for twelve to twenty hours, receiving during that 

 time its shell, which is formed by calcareous 

 excretions of the glandular walls of the uterus. 

 The external layer of the shell is most variable, 

 and may be smooth and shiny, as in that of a 

 Woodpecker, due to the small amount of calcine 

 salts, or rough and chalky, as in that of a 

 Cormorant, owing to an excessive amount of 

 these. Then comes the deposition of the colour 

 pigments, in such eggs that are spotted, this 

 apparently always taking place shortly before 



