298 



coming ou. If they are too young to cater for themselves, 

 remove the cock for a week or two, and leave them with the 

 hen to finish rearing. Then remove the young and put back 

 the cock, when another nest will probably be obtained. These 

 precautions are, of course, unnecessary when the parents do 

 not illtreat their young; but in any case remove the young as 

 soon as the}' can look after themselves. 



*'H few points ou Birt)5 lEoQS." 



By J. MCDONAGH, M.R.C.S., F.Z.vS., F.LvS. 



These few points are culled from two cases recently put up 

 in the Natural History Museum, Ground Floor, at entrance 

 of fifth alcove ou the left. 



1. — Structure : 



{a). Yolk: That part of the egg where development begins; 

 it is enclosed in a membrane called the bitelline mem- 

 brane, thereby separating it from 



{b). White. This forms the food of the developing chick, it is 

 thicker in parts, and these thickened bauds as they 

 real)}' are, are called chalazae. They pass between the poles 

 of the &gg and yolk serving to keep the latter in position. 



{c). Outside the white is a fibrous shell membrane, consisting 

 of two layers with a small air chamber Ijetween, no air is 

 present in perfectly fresh eggs. This air accounts for the 

 depression on the white one sees when opening a hen's egg 

 for breakfast. 



{d). 5'A^// generally consists of three layers, an iuner, middle, 

 and outer, made up chiefly of salts, and the absence or 

 presence of the salts of calcium in the outer layer modify 

 the character of this layer. When very poor in calcium 

 salts the shell is smooth and glossy, when rich in calcium 

 salts shell has rough and chalky appearance. 



The colour of the shell depends on pigment layed 

 down in either middle or outer layers during the passage 

 of the egg along the oviduct. 



Then comes a card showing the difference in thickness 



