490 EMBRYOLOGY OF THE TURTLE. Part III. 
of different sizes, each set being equal in number to the average number of eggs 
It thus 
require more than one year for their full development. 
laid by the species under observation. became evident that the eggs 
Once upon this track, it 
appeared practicable to determine how long a period this growth embraces; for, 
as soon as it could be ascertained how many eggs different species of Turtles 
lay, there was a standard of comparison obtained for the investigation of the ova- 
ries; and, as I early learned that the species most common about Cambridge 
exhibit marked differences in that respect, I selected these species for my first 
I have 
studies. Chrysemys picta lays always between five and seven egys. 
never observed as few as four, and only occasionally eight. Nanemys guttata 
lays generally two or three; I have only once or twice found four eggs in its 
nest, and three times in its ovary. There was therefore no chance of making 
any mistake, when comparing the number of their ovarian eggs with that of 
the eges they lay, after I had ascertained that a few weeks before the breed- 
ing season there are the same numbers of mature eggs to be found im the ovary 
as these species usually lay in the spring. I felt still greater confidence in the 
possibility of coming to precise results, after I had found again and again the 
very same number of eggs in the oviduct,’ and noticed that at that time another 
set of eggs could be readily distinguished, of the same number as the larger eggs 
left in the ovary. Indeed, the difference between this largest set of ovarian eggs 
and the smaller ones is so great, even at the time when the eggs about to be 
laid are still in the oviduct, that they are distinguished at the first glance; for, 
though they have unquestionably to remain another year in the ovary, they are 
already nearly as large in diameter as those which have just left it. 
With a knowledge of these facts, it was easy to arrive at a full understand- 
ing of the normal periodicity in the growth of the ovarian eggs. It soon became 
plain, that shortly before the period of laying there were not only two, but as 
many as four, distinct sets of eggs in every ovary; and that, after the largest 
set had been laid, a new small set 
smallest eggs of variable size. It now 
to be answered. What is the age at 
time such differences between its eggs? 
Chrysemys picta® it was ascertained, that, 
tains only eggs of very small size, not 
1 Tt has already been stated above that the eggs 
of one ovary are not necessarily received into the ovi- 
duct of the same side of the animal, but may be taken 
up by the fallopian tube of the opposite side. See 
Part II., Ch. 1, Sect. 13, p. 288. 
Was 
the innumerable 
seemed that a single question remained 
the Turtle for the first 
Upon opening large numbers of young 
started from among 
which discloses 
up to their seventh year, the ovary con- 
distinguishable into sets; but that with 
2 Comp. Part II., Ch. 1, Sect. 14, p. 292, where 
the most prominent characters of this species and the 
differences in its size, in successive years, are given 
approximately, for the first twenty-five years of its 
existence. 
