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collected when fresh, just at the beginning of the period of incubation. 
Some species lay at intervals and begin incubating the first egg, so that 
the young do not hatch at the same time. A few tools are needed: (1) 
egg drills, from about inch up to | inch in diameter; (2) curved 
metal blowpipe (a straw or section of grass stem may be used in emer- 
gency) ; (3) fine, curve-pointed scissors; (4) fine, curve-pointed forceps; 
and (5) embryo hook. A small, hard-rubber piston syringe is very 
handy, but the collector can get along by blowing a mouthful of water 
through the blowpipe. 
A hole is drilled in one side of the egg, no larger than will allow the 
contents to be emptied conveniently. A hole that is too large is unsightly 
and weakens the shell. Holding the egg hole down, place the tip of the 
blowpipe near the hole and blow gently, until the compressed air forces 
the contents out. If the egg is incubated, the liquid part may be blown 
out, and by careful work with forceps and scissors the remainder may be 
pulled out piecemeal. If the egg is considerably incubated, and hairs or 
feathers are noticed, the job is more difficult, and after blowing out the 
softer parts, a solution of pancreatin in water may be injected and the 
egg set in a warm place until the contents are digested enough to be rinsed 
out. Always rinse out the inside of a blown egg with a mouthful of water 
forced through the blowpipe or syringed into the shell, before setting it 
aside to drain on a piece of cotton. Blowing an egg that has a chick in 
it is a tedious and messy process, and unless the egg belongs to a very 
rare species, and the collector has the patience and skill to carry through 
a long operation, the egg is better left in the nest. A well-incubated egg 
can usually be told by loss of the original pearly tint, dull colour in thin- 
shelled eggs, and polished surface of shell in other cases. The appear- 
ance is rather difficult to describe, but is easily recognized by a person 
who is familiar with the appearance of the fresh egg. Eggs that have 
characteristic spots or other markings on their shells should be kept from 
wetting if possible, as the pigment is often solvent in water when fresh, 
and the pattern is easily smeared or obliterated. 
Oologists sometimes obtain eggs that are too far advanced in incuba- 
tion to be blown without splitting the shell. In such cases the embryo 
may well be preserved in alcohol or formalin and turned over to some 
embryologist who is interested in the ontogeny and phylogeny of birds. 
An egg is totally useless unless the identity of the parents is known. 
In some cases, the shape or colour of the egg is unique, and the egg can 
be named by inspection, but in most cases it is necessary to have a good 
sight identification of the parents, and if the collector is not able or com- 
petent to do this, one of the parent birds must be secured and preserved 
for identity. 
To avoid mixing specimens, each egg in the set is marked near the 
blowhole with soft black pencil with the same number, the A.O.U. num- 
ber of the bird, and the set mark. The set mark consists of the collector’s 
field number of the set and the number of eggs in the set. A robin would 
have the A.O.U. No. 761, followed by the collector’s field number, and 
if it was his first set of four eggs, by the fraction The second set of 
four eggs would be marked 2i. If the nest is preserved, the letter N is 
usually added. 
