33 



ment to the Detroit hatchery, the following counts were 

 made : 



April 17th, 1 p.m., 252 eggs taken at random from a 

 tub, after stirring the eggs in the tub, were examined with 

 the following results : 



Segmented normally (i.e., impregnated) 141= 56^ 



Unsegmented, normally (not imx^regnated) 26= 11^ 



Injured by esca^^e of yolk (white eggs) 85= 33fo 



Total 252=100,<^ 



The eggs marked as unimpregnated were set aside, 

 and were found to be still unsegmented after twenty-four 

 hours. 



This was several times repeated on other lots of eggs, 

 with similar results. 



It shows that about 33^ of the eggs are injured mechan- 

 ically by the rujDture of the protoplasmic investment of the 

 yolk, while only about 11^ perish from lack of impregna- 

 tion. Even su23er{icial examination shows that in nearly 

 every case this rupture of the yolk takes place over the 

 oil-globule. A consideration of the mechanical arrange- 

 ment of the parts of the eggs shows that this is its weak 

 spot. 



In the natural position the yolk sphere lies with its 

 lower half against the egg membranes. These membranes, 

 therefore, support this half of the yolk, surrounding it as 

 if it were resting at the bottom of a cuj). 



The upi^er half of the yolk is, on the contrary, not of 

 the same form as the investing membranes ; its spherical 

 surface is interrupted by the protruding oil-globule. 



The result of this arrangement is that when any pressure 

 is brought to bear on the egg membranes, so that the space 

 within which the yolk lies is reduced, the yolk is able to 

 resist this pressure by titting itself against the egg mem- 

 brane at every part of its surface except over the oil- 



