132 MAINE AGRICULTURAL EXPERIMENT STATION. I 914 . 
be started off by some adequate stimulus (probably in the case 
of the yolkless eggs by the presence of a yolk in the oviduct 
which is later expelled into the body cavity) and may then 
continue to completion without the presence of the yolk. These 
results with artificial yolks indicate that the stimulus may be 
mechanical but the experiments of Tarchanoff § and unpub- 
lished work done in this laboratory also show that an egg is not 
always formed around an artificial yolk introduced into an 
oviduct which is in functional condition. Until the other con- 
ditions necessary for the formation of eggs with artificial yolks 
are determined it cannot be certainly said that the only stimu- 
lus necessary is mechanical. 
That the amount of albumen secretion of the oviduct is re- 
lated to the degree of the stimulation by the yolk is shown by 
the significant correlation between the weight of the yolk and 
the weight of the albumen. Since the secretion of the duct 
does not begin until the yolk has completed its growth and 
severed its connection with its follicle this seems to be the 
only possible explanation of the correlation. To this evidence 
that the degree of stimulation influences the amount of secre- 
tion may be added that from abnormal eggs which contain 
unusual large or small quantities of yolk. On the one hand are 
the double and triple yolked eggs and on the other the “cock- 
eggs” or “witch-eggs” which contain little or no yolk. Pearl* 
(To) showed that “the relation of the observed size of the 
entire egg (measured here by the weight) to the number of 
yolks is very accurately described by a parabola.” He pointed 
out that this indicated that the amount of albumen secreted was 
related to the amount of the immediate mechanical stimulation 
due to the quantity of yolk present in the oviduct. 
The formation of the egg membrane is a discrete process. 
As an egg passes from the albumen portion into the isthmus 
as much of it as is within the isthmus is covered with mem- 
§ Tarchanoff, J. R. hoc. cit. 
* Pearl, R. A Triple Yolked Egg. Zoologischer Anzeiger, Bd. 
XXXV, pp. 418-423, 1910. 
t Coste, M. Histoire du development des corps organises. Paris, 
1874. 
