at and a turtle, the real relationship in the first case is
much closer than in the second. This is perhaps most easily seen in
the scaly legs of both bird and reptile. Another remarkable
resemblance lies in the fact that in both cases the eggs are large,
well stored with nourishment, and protected by a resistant shell.

So few people know the turtle's egg that it will be better to describe
that of the hen, which it largely resembles. Underneath the hard shell
is a tough but flexible membrane which lies against the limey coating,
except at the blunt end, where a separation between the two gives room
for a bubble of air. Inside of this shell and its membrane lies the
white of the egg, which is nourishment for the chick, though not
nearly so rich as the yolk. This, besides the albumen which it
contains, is stored with large quantities of fat. It will be
remembered that upon breaking a hen's egg and dropping it into a bowl,
the yolk holds together because it is enclosed in a delicate sac. As
the yolk falls into the bowl there floats to the top of it a lighter
yellow spot as big as the end of a lead pencil. This is all of the egg
which thus far represents the chick itself. All the rest is
nourishment. This disk already consists of three reasonably
distinguishable layers of cells, which grow rapidly different from
each other. They spread and bend and twist, forming the young chick
and a set of organs which serve for its protection and maintenance
during its embryonic life. Within a few days these accessory organs
will have formed distinctly. Within the upper half of the yolk will be
found the small developing chick, which for the first thirty-six hours
of its development passes through a stage not unlike the fish, or the
earlier steps of the turtle. Within a few days it becomes clearly
evident that this creature is to be a bird, though it is much longer
before it is clearly a chick.

This embryo is so soft that it is almost like curd in thickened milk,
and could be very easily destroyed were it not for a protective device
which Nature has employed. It seems necessary that it should be
protected with the utmost care. The matter will be better understood
if we recall a common experience. Almost everyone has tried to
dissolve some substance in water in a vial. If the bottle be filled
with fluid to the top and corked it is very difficult to shake up the
contents. Even vigorous agitation produces little movement of the
material