P.] OPENING THE EGG. 241 



at the bottom of the basin a mould, e.g. a flat piece of 

 lead with a concavity on the upper surface, in which 

 the egg may rest securely without rolling. Pour into 

 the basin so much of a '75 per cent, solution of sodium 

 chloride warmed to 38° as will cover the egg com- 

 pletely. With a sharp tap break through the shell at 

 the broad end over the air-chamber, and let out as 

 much air as has already been gathered there. Unless 

 this is done, 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, inconvenience 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 doin^ 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 in 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 38°C. 



B. Examination of the blastoderm in situ. 



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

 simple lens of low power. Observe : — 

 E. 16 



