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Short Papers and Notes. 
The Development of the Chick. 
T a recent meeting of the Leeds Naturalists’ Club and 
Scientific Association, an embryological subject 
engaged the attention of the club, under the direction 
and guidance of the President (Professor Miall, 
F.G.S.), viz., the “* Development of the Chick.” The 
subject was treated from an elementary point of view, and was 
illustrated by diagrams on the black-board, and afterwards by the 
examination and dissection of chick embryos in various stages of 
development. The egg was shown to consist externally of the 
shell, lined by shell membrane; then the white; and lastly the 
yolk, which was contained in a delicate membranous sac. The 
shell membrane is double at the broad end, and encloses an air- 
space. This space does not, however, exist*in new-laid eggs, but 
its formation commences soon afterwards. The yolk is anchored 
at opposite poles by thick twisted bands, called chalaze. The 
ovary produces the yolk only, and the white is secreted as it passes 
down the oviduct. The motion is of a spiral nature, and thus the 
white is laid round the yolk in twisted or spiral bands. The yolk 
is not uniform in density ; one part, that from which the future 
embryo is developed, usually called the “ white yolk,” is lighter, 
and therefore always forms the upper surface of the yolk. The 
yolk, again, is lighter than the semi-fluid white, and floats in it in 
close proximity to the upper part of the shell, and in whatever 
position the egg lies, and however often its position is changed the 
white yolk is thus placed so as to receive the greatest amount of 
heat from the body of the hen. As the chick develops, the chalazze 
secure it, and prevent injury from friction between the yolk and the 
white. 
From this point the demonstration was of a practical character 
on partially incubated eggs. The President showed that the 
egg should be opened for such purposes by pricking the broader 
end of the shell, so that when the upper surface is penetrated the 
weight of the shell contents drives out the air contained between 
the two layers of shell membrane at the broad end and leaves a 
space beneath the upper surface, so enabling the operator to re- 
move the shell without injury to the embryo. The shell is then 
cut through equatorially by strong scissors, the operation being 
conducted in a slightly saline solution heated to 41° C. The 
embryo, being lightest, then floats to the top, and may be removed 
in a watch glass or on a cover from the yolk sac by dissection. 
