The alligator and its alliesReese, A. M. (Albert Moore)
Science
The alligator and its allies
Reese, A. M. (Albert Moore)
Alligators
Voeltzkow (78) states that the form of the egg of the Madagascar
crocodile is very variable. No two eggs in the same nest are exactly
alike, some being elliptical, some “egg-shaped,” and some “cylindrical
with rounded ends.” The average size is 68 mm. by 47 mm., shorter and
thicker than the average alligator egg.
When first laid, the eggs are pure white, and are quite slimy for a few
hours, but they generally become stained after a time by the damp and
decaying vegetation composing the nest in which they are closely packed.
The shell is thicker and of a coarser texture than that of the hen’s
egg. Being of a calcareous nature, it is easily dissolved in dilute
acids.
The shell membrane is in two not very distinct layers, the fibers of
which, according to S. F. Clarke, are spirally wound around the egg at
right angles to each other. No air-chamber, such as is found in the
hen’s egg, is found in any stage in the development.
In most--probably all normal--eggs a white band appears around the
lesser circumference a short time after being laid. This chalky band,
which is shown at about its maximum development in Fig. 1_a_, is
found, on removal of the shell, to be caused, not by a change in the
shell, but by the appearance of an area of chalky substance in the
shell membranes. Clarke thinks this change in the membrane is to aid
in the passage of gases to and from the developing embryo. Generally
this chalky area forms a distinct band entirely around the shorter
circumference of the egg, but sometimes extends only partly around it.
It varies in width from about 15 mm. to 35 mm., being narrowest at its
first appearance. Sometimes its borders are quite sharp and even (Fig.
1_a_); in other cases they are very irregular. If the embryo dies the
chalky band is likely to become spotted with dark areas.
The shell and shell membrane of the egg of the Madagascar crocodile are
essentially the same as those just described, except that the shell is
sometimes pierced by small pores that pass entirely through it. The
same chalky band surrounds the median zone of the egg (78).
The white of the egg is chiefly remarkable for its unusual density,
being so stiff that the entire egg may be emptied from the shell into
the hand and passed from one hand to the other without danger of
rupturing either the mass of albumen or the enclosed yolk. The albumen,
especially in the immediate neighborhood of the yolk, seems to consist
of a number of very thin concentric layers. It varies in color, in
different eggs, from a pale yellowish white, its usual color, to a very
decided green.
As might be expected, no chalazæ are present.
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