POLYEMBRYONIC DEVELOPMENT IN TATUSIA 567 
which the egg came; the fifth, the age of the mother; the sixth, 
the number of the figure, in case the specimen is illustrated in 
the paper; the seventh, remarks. Unless otherwise stated, under 
remarks, the vesicle was taken from the right to left horizontal 
groove of the uterine cavity. In most instances differences in 
size indicate differences in the degree of differentiation among the 
several blastocysts, although there is some variation in vesicles 
showing corresponding differentiations. 
The table brings out several interesting points, and to those that 
will not be specifically treated in subsequent sections we must 
direct a few remarks. 
_ In twenty-nine of the thirty-two cases listed the ovary from 
which the egg came was determined; and the record shows that 
fourteen were derived from the right ovary and fifteen from the 
left, thus indicating that there is no tendency for one ovary to 
function more frequently than the other. In two of the remaining 
cases I failed to make a record on this point, but in the third (No. 
297) both ovaries were enlarged. This would indicate that occa- 
sionally the two ovaries function simultaneously, although in this 
particular case I was not able to find a second egg. There is of 
course the possibility that the one ovary gave off an egg which 
failed to become implanted, and that a second ovulation, involving 
the other ovary, followed immediately. 
It was stated above that the ‘old’ females, that is females which 
have previously borne young, breed first, and that the second year 
virgin females come on later. The table brings these facts out 
clearly. Thus, of the eighteen cases with complete records, which 
were taken in October, fourteen (Nos. 230, 287, 288, 291, 292, 295, 
297, 300, 304, 305, 309, 320, 325, 326) were from old females, while 
only three were from virgin females, that is females that had never 
before borne young. Of the eleven cases involving second year 
females, eight vesicles (Nos. 243, 244, 245, 251, 258, 259, 261, 335) 
were taken between November first and eighth; while two of the 
remaining three were secured late in the month of October, both 
on the 26th (Nos. 311, 315). Finally, of the three vesicles 
obtained from the first year females, that is females that had 
been born during the previous winter or spring, two were taken 
