A GUIDE FOR KEEPERS OF POULTRY 125 
incubator; but this should always be done, as the infer- 
tile eggs or the dead ones may cause loss of some of the 
fertile eggs. There are numerous egg-testers on the mar- 
ket. They may be procured of any incubator maker. 
Experts in testing are able to make a very satisfactory 
test simply by holding the egg by surrounding it with 
the thumb and forefinger before a strong light. It. is 
best, however, to use a tester. A strong light from a 
lamp or electric light should be used. The first sign of 
fertility may be noticed after the first day, as a reddish 
spot will show about the center of the egg when held 
before the light in the tester. This spot is quite dim at 
first but gradually becomes more pronounced until it is 
quite a deep red in the center. The spot should be about 
as large as a cent. Two days later a black spot may be 
observed, this being the rudimentary heart, and a little 
later ‘the spider” appears. This is the eyes of the embryo, 
which appear like a black spot, about the center of the 
egg, from which extend veins filled with blood to repre- 
sent the legs of the spider. Later the body of the egg 
shows increasing opaqueness, with blood veins around 
the inner side of the shell and still later the egg appears 
black with semi-transparent spaces at the lower end and 
the point. The air-space at the point gradually disap- 
pears if the chick is growing normally. About the 15th 
or 16th day a fertile egg shows a large air-space, the 
remainder being opaque. 
If an egg is infertile it remains transparent or as we 
call it “clear.” A very faint pinkish spot rather smaller 
than a cent may show in an infertile egg which contains 
a very yellow yolk, but this appearance does not change 
as time goes on. All such eggs should be removed the 
5th day. Later it will be found that some eggs which have 
