PROGRESS IN BIOLOGICAL INQUIRIES, 1926 619 
survive to reach the dinner plate is what counts. It is here that we believe 
we have a very great advantage over the fish culturists, for we are able to keep 
the young animals, with comparatively little work and at small expense, until 
they have reached a length of 1% to 2 inches, when they have definitely 
passed through the most critical stage of life. At this size they have devel- 
oped a hard shell, are able to get about more rapidly, and they are no longer 
the utterly helpless creatures they were when first hatched. They no longer 
can be destroyed by mice, small birds, crabs, or small fish. We are able to 
bring the animals to this point within about six months, when winter fed, 
and within a year and six months if permitted to hibernate. The loss among 
these young animals seldom has exceeded 15 per cent, which is a lower mor- 
tality than commonly occurs among young chickens. 
Furthermore, we have some evidence that a fair percentage of the animals 
liberated live and grow in the wild state, for of the comparatively few (con- 
sisting of only several hundred) individuals liberated at Beaufort each year, 
from 1914 to 1928, several have been recovered; and the rate of growth in 
these animals compared very favorably with those of the same age kept in 
captivity. It is believed, therefore, that the diamond-back terrapin cultural 
work along the lines now pursued at Beaufort promises to bear fruit from 
fifty to seventy-five if not one hundred fold. 
When it was said that the work had passed the experimental stage it was 
not intended to leave the impression that experimentation had ceased. There 
is much to learn, and at least 10 definite sets of experiments, involving 21 lots 
of terrapins, are now under way. As time is less of an item in the life of a 
terrapin in North Carolina than to the proverbial hog in Louisiana, some of the 
experiments will have to run a long time before definite results may be ex- 
pected. For example, several years ago, as the result of a conference with a 
cseneticist of the Bureau of Animal Industry, a series of breeding experiments 
was planned, and the animals to be used were segregated in the spring of 19238. 
We have yet to wait another year before we can be sure that the offspring is 
from the particular males selected for the experiments. Then we will be 
obliged to wait at least six years longer for this offspring to mature and for the 
second generation. 
The slow growth and the long time between generations naturally brings the 
question to mind: How long does a terrapin live? Or, what is its normal span 
of life? This is a question that does not yet admit of an answer, and I am 
not sure that we will live long enough to learn definitely, unless a genius should 
appear who can find a more reliable way of reading the age than by the growth 
rings on the carapace. 
A lot of about 370 wild terrapins is on hand. The lot is composed of a few 
animals secured in 1902, others that were obtained in 1909, and the rest in 
1912. Only about half a dozen of these animals have died during the many 
years they have been in confinement, and they were all adult breeding terrapin 
when secured. The only certain indication of old age of some of these animals. 
is the smoothness of the shells, for the growth rings have disappeared, quite 
probably due to wear. For several years in succession egg production fel! off, 
and just as we were becoming convinced that ‘old age” had overtaken them, 
this lot of old breeders came back last season with about the largest number of 
eggs and young ever produced. Consequently, we will have to guess again. 
Other experiments consist of cross breeding two species of diamond-backs, 
comparison of rate of growth of hybrids with animals of pure blood, compari- 
son of growth of the offspring of wild terrapins, that have been confined, with 
that of animals grown in captivity. Other experiments have to do with space 
requirements of the animals, the proportion of males to females necessary to 
insure fertility of the eggs, and the natural sex ratio. Among all the groups 
of animals that have been grown in captivity the males are very greatly in the 
minority. These lots, however, all consist of selected animals. Two unselected 
lots, each consisting of 300 terrapins, have now been set aside and will be 
retained until the sexes become distinguishable. 
Winter feeding of young animals is being continued. One of the practical 
results derived from this work already has been referred to, for it was shown 
that a year’s time may be saved in bringing the animals to a size at which it 
is thought safe to liberate them. Similarly, a year’s time is saved in bringing the 
animals, when held in captivity, to sexual maturity and to marketable size. 
Our data indicate that a somewhat larger percentage of the animals survive 
when handled in this way, than if allowed to hibernate. 
