438 PRACTICAL DIRECTIONS. [APP. 



the presence of air in the air-chamber will cause the 

 broad end to tilt up. At this date there will be 

 very little air, but in eggs of longer incubation, in- 

 convenience will be felt unless this plan be adopted. 



Instead of being broken with a blow, the shell 

 may be filed through at one point, and the opening 

 enlarged with the forceps; but a little practice will 

 enable the student to use the former and easier- 

 method without doing damage. 



With a blunt pair of forceps, remove the shell 

 carefully bit by bit, leaving the shell-membrane 

 behind; begin at the hole made at the broad end, 

 and work over the upper part until about a third or 

 half of the shell has been removed. 



Then with a finer pair of forceps remove the 

 shell-membrane; it will readily come away in strips, 

 torn across the long axis of the egg in a somewhat 

 spiral fashion. The yolk and embryo will now come 

 into view. 



It is the practice of some simply to break the egg 

 across and pour the yolk and white together into a 

 basin, very much as the housewife does. We feel 

 sure, however, that the extra trouble of the method 

 we have given will be more than repaid by the 

 results. 



During this time, and indeed during the whole 

 period of the examination of the embryo in situ, the 

 basin and its contents must be maintained, either by 

 renewal of the salt solution, or by the basin being 

 placed on a sand-bath, at about 38C. 



B. Examination of the blastoderm in situ. 



This may be done with the naked eye, or with a 

 simple lens of low power. Observe : 



