THE DIAMOND-BACK TERRAPIN. 



107 



young a stage in the development of the terrapins to be of any advantage to the terrapin 

 eulturist. A comparison of this 19 12 study in the effect of selection with that of the 

 "selects" of the 1910 brood emphasizes this point. Selection for size occurred in the 

 1910 brood when the terrapins were 4 years old. The egg production from these 

 "selects" was especially large. In the 1912 lot the egg production is not above normal 

 for either group of terrapins fed one winter and remaining unselected. Selection as 

 early as the second year is premature,, since the terrapin at that age has not reached 

 one-half its adult size, and there may be many influences after the second year to retard 

 growth in what then appears as an exceptionally healthy and rapidly growing terrapin. 

 The Texas brood of 1912, numbering 24 in 1916, 1917, and 1918, and 14 from 

 1919 to 1921, has shown greater average growth and produced eggs in 1918, a year 

 earlier than the Carolina terrapins of the same age. The possible earlier arrival of 

 the offspring of Texas stock at sexual maturity may be hereditary in character. All 

 the antecedents of this Texas stock were from the marshes of Texas, where the longer 

 growing and laying season with the very limited hibernation period would normally 

 tend toward the occurrence of an earlier maturing animal than would be found in nature 

 in North Carolina. This early maturing characteristic may have become inherent in 

 the Texas stock. 



1913 BROOD. 



The 1913 brood was originally divided into two lots — one hibernated while the 

 other was fed. Of the fed lot the largest 100 terrapins were selected for further 



MM. 



150 



140 



130 



120 



110 



100 



90 



80 



70 



60 



50 



40 



30 



20 



10 



1913 1914 1915 1916 1917 1918 1919 1920 



Fig. ??. — Growth ol 1913 broods of original Carol ma and Texas brood stocks. 

 Keg production and hatch per female per year expressed, respectively, by 



figures oil the curve. — , Offspring of Carolina brood stock, selected 



for large size in the spring of 1914; .offspring of Texas brood stock, 



fed one winter; , offspring of Texas brood stock, hibernated 



study. These selected individuals at 6 years of age did not average 4K inches, 

 though, of course, there were some over 5 inches in length in the lot. Neither 

 had they laid any eggs. There was, however, in the seventh year a small produc- 

 tion of eggs and young in this stock. Their slowness of growth can not be well 



