414 THE AMERICAN NATURALIST. 
clear. of all obstructions, whether they be abortive eggs, blood 
clots, feathers which rarely grow from its walls, or parasites 
which find their way into it. These bodies are taken up by 
the egg, and become imbedded in it. In one of the cases 
recorded in this paper the obstruction or small “egg” (Fig. 2) 
has been pressed through the albumen, through the vitelline 
membrane, and thus into the yolk itself. It is evident that 
inclusions of the first type are not true eggs in any strict sense, 
since, so far as known, they contain no protoplasm. 
The theory of yolk-hernia will not explain the second class 
of abnormalities, such as double or triple yolk eggs. We have 
here a case of fusion of the albumen in two or more ova, which 
are treated in the uterus as one egg and surrounded by a single 
shell. This process is sometimes complicated by the inclusion 
of a third egg of normal size and already covered by a hard 
shell. These conditions may be brought about by irregularities 
in the mechanism of the oviduct, as when any given egg does 
not receive its shell and is not laid before it encounters others 
coming down the oviduct at the same time. 
According to Duval, an egg usually spends thirty hours in 
the oviduct, twenty-four of which are passed in the uterus, and 
if the fowl lays once in forty-four hours a single egg will be 
found in the oviduct at any given time. When the intervals of 
laying become shorter, however, an egg may be found at either 
end of the tube. In some of the cases described three ova must 
have been in the tube and collided there, owing to disturbances 
in the normal rhythms. 
