238 



THE UNFERTILISED EGG AS A 



[PT. Ill 



The above data were all obtained without any ad hoc investigation of the probable 

 errors involved in weighing eggs and parts of eggs. An elaborate study by M. R. Curtis 

 in 1 9 1 1 gave the following results on Gallus domesticus : 



Actual 

 weight in gm. % 



56-04 100 



33-22 59-26 



16-31 29-14 



6-28 ii-i8 



0-23 0-42 



Whole egg 

 Albumen 



Yolk 



Shell and membranes 

 Error 



But though this is the case with the egg in its natural state, the solid 

 matter is concentrated much more in the -yolk than in the white, 

 so that, as the analyses of Poleck and Iljin, for instance, show, for 

 dry weight the conditions are exactly reversed. The egg-white may, 

 indeed, be regarded as the principal reservoir of water for the embryo 

 which develops on dry land, and this is a point which will be dis- 

 cussed later (see Section 6-6). The eggs of different breeds of hen 

 vary to some extent in the relative weights of shell, white and yolk; 

 but, although it is difficult to lay down any general rule, these varia- 

 tions do not greatly exceed the variations due to factors connected with 

 the individual hen. Iljin's lightest shells make up about 7 per cent, 

 of the G,gg weight and the heaviest not more than 11-5 per cent. 



