74 THE PASSENGER PIGEON IN PENNSYLVANIA 



about half an ounce, with rounded ends similar, instead 

 of one end pointed, as in the case of domestic fowls; 

 and the shell is white. Birds are classed as verte- 

 brates, but do not suckle their young, nourishing them, 

 as explained in earlier chapters, as regards pigeons, 

 with partially macerated food from the pouch of either 

 parent bird, acted upon by its own organs of digestion ; 

 and' which they are able to disgorge at will, similar 

 to ruminating qua'drupeds. The young are produced 

 in an animated state, from the eggs, by the effects of 

 constant warmth, as the parent pigeons sit alternately 

 upon the nest. 



When the Ggg is first produce:\ the future squab 

 is indicated by a little germ-spot, barely the size of a 

 single oat-grain with hull and shuck removed ; without 

 power of breathing atmospheric air and receiving nour- 

 ishment into its mouth, until the incubating period has 

 elapsed. To watch the development in the Ggg is an 

 interesting experiment and full of suggestive instruc- 

 tion. The structure is so balanced, that to view tfie 

 little germ-spot it is only necessary to lay the egg on 

 its side' and remove a portion of the shell, when the 

 germ will be seen lying immediately under the aper-. 

 ture. In whatever way the egg may he turiied, the 

 germ-spot presents itself at the highest point, provided 

 the egg be laid on its side, and that the living prin- 

 ciple has not been extinguished. As growth proceeds, 

 mxanipulation becomes easier, but it is best to immerse 

 the egg in water, before removing the shell, and to 

 keep it submerged chtring the examination. 



