DIAMOND-BACK TERRAPIN CULTURE 
33 
Tables 8 to 15 show in detail the approximate number of eggs produced each 
year, the number of young hatched, and the percentage of fertility. It is difficult 
to account for the wide yearly fluctuations in the fertility of the eggs that have 
occurred in nearly all lots on hand. In general, the highest percentage of fertile 
eggs has been produced by those lots having the largest proportionate number of 
males. Examples of a high degree of fertility, as already shown, occurred in the 
wild brood stock (Table 8), in which the ratio of males to females has usually been 
about 1 to 2. A very high percentage of fertile eggs was laid from 1918 to 1925 by 
a small brood hatched in 1909, in which there also was one male to two females. 
During the first three years in which eggs were laid by this brood the percentage of 
fertile ones ran very low, and then, as shown by the table, fertility suddenly increased 
and thereafter remained fair to very high. 
The lowest percentage of fertility among the older broods, for which considerable 
data are at hand, occurred in a lot belonging to the brood of 1911 (Table 11), which 
was allowed to hibernate each winter. This lot now (1928) consists of 3 males and 
35 females. Egg laying began in 1918. Since no males were penned with the females 
until the fall of 1919, the eggs for the first two summers were not fertile and have not 
been considered in these data. Fertility has varied from 23.6 to 89.7 per cent dur- 
ing the period 1920 to 1926, inclusive, with an average fertility for the whole period 
of 64.8 per cent. Another lot of the same brood (1911), consisting of 38 females 
(originally penned with the lot just discussed) and 3 old males taken from the original 
brood stock, has produced consistently a higher percentage of fertile eggs over the 
same period of years. Fertility in this lot was the lowest in 1921, when only 71.4 
per cent of the eggs hatched, and it was highest in 1925, when 93.4 per cent of the 
eggs were fertile, the average fertility for the entire period being 81.5 per cent. It 
seems probable, although by no means certain, that the higher fertility in the last- 
mentioned lot may have been due to the old and fully matured males that were 
introduced, whereas it is not known that the young males of the other lot were all 
mature when eggs first were produced. 
It is a well-known fact that all females of one age do not become mature at the 
same time. Some females, in fact, require several years longer to reach sexual 
maturity than others. The same very probably is true of the males. This subject 
is discussed more fully in another section of this paper (see p. 56). The fact that 
the percentage of fertility in the lot penned with young males increased each year 
(Table 11) until 1925 lends support to the belief that the number of mature males 
present may have been insufficient. It will be seen, also, from Table 11 that the 
lot penned with young males each year produced a larger number of eggs than the 
other one, notwithstanding that there were three more females in the pen with the 
old males. This suggests earlier maturity for a larger proportion of the females 
penned with young males than for those penned with old males, and this, too, may 
have had a bearing upon fertility in relation to the number of males present. 
Owing to such great fluctuations in egg production, it can not be stated definitely 
that one of the two lots of the brood of 1911, compared in the preceding paragraphs, 
produced a greater number of eggs than the other because it contained a larger num- 
ber of mature females, for the difference in egg production, as just shown, may have 
