DIAMOND-BACK TERRAPIN CULTURE 
55 
pin culturist, for then they could be eliminated at an early age and before they had 
become much of a liability. It is not practicable to do this, however, for frequently 
the slow-growing animals suddenly begin to grow fast and in a comparatively brief 
time overtake those that grew fast earlier in life but discontinued their rapid growth. 
An excellent example of the changes in the rate of growth of terrapins is found in 
the brood of 1912 (Table 24). In this instance, from a total of about 800 yearling 
animals 100 of the largest were selected and placed in a separate pen; also 100 of the 
smallest and runtiest were selected and placed in an adjacent pen. Food and treat- 
ment and the general environment were made as nearly identical as possible. Meas- 
urements of the two lots at the time of selection (September 13, 1913) are not avail- 
able. The animals were measured in the following spring (April 29, 1914), however, 
m 1921 1922 1923 m 1925 7926 1927 
Figure 11. — Rate of growth of two selected lots of the 
brood of 1920. Line D represents offspring of domestic 
stock and line W that of wild stock 
1920 1921 1922 1929 I92f 1925 /92G 1927 
Figure 12. — Rate of growth of an unselected lot of hybrid 
terrapins (Carolina males and Texas females) of the brood 
of 1920 
and of course not much growth had taken place during the interval. The 100 
“selects” all survived until spring and had an average length of 65 millimeters. The 
100 “runts” had diminished to 89, and these animals had an average length of 32.3 
millimeters. On October 6, 1917, the selects, which then numbered 89, consisted of 
18 males and 72 females. The males had an average length of 88.7 millimeters and 
the average length of the females was 98 millimeters. On the same date the runts 
numbered 69 and were composed of 13 males and 56 females. The males averaged 
87.2 millimeters in length and the females 109.5. The combined average length of 
male and female “runts,” therefore, was greater than that of the “selects.” The 
lead then secured by the “runts” has been maintained to the present time (1928). 
It is not known that identical results would be obtained if a similar experiment 
were to be undertaken. The selection experiment with the brood of 1912, together 
