172 THE RATE OF GROWTH [ch. 



We may want now and then to make use of scanty data, and find 

 a rougli estimate better than none. The giant tortoises of the 

 Galapagos and the Seychelles grow to a great age, and some have 

 weighed 5001b. and more; but the scanty records of captive 

 tortoises shew much variation, depending on food and climate as 

 well as age, Ninety young tortoises brought from the Galapagos 

 in 1928 to the southern United States weighed on the average 

 18J lb., and grew to 44-3 lb. in two years. Six taken to Honolulu 

 weighed 26 J lb. each in 1929, and 63 lb. each the following year. 

 Another, kept in CaHfornia, weighed 29 lb. and 360 lb. seven years 

 later, but only gained 65 lb. more in the next seven years. Growth, 



1899 1906 1913 



Fjg. 41. Approximate growth in weight of Galapagos tortoise. 



as usual, is quick to begin with, slower lat^r on, and in the old giants 

 must be slow indeed. If we plot (Fig. 41 ) the three successive weights 

 of the CaHfornian specimen, at first they help us little; but we can 

 fit an S-shaped curve to the three points as a first approximation, 

 and it suggests, with some plausibility, that, at 29 lb. weight the 

 tortoise was from two to three years old. A loggerhead turtle, 

 which reaches a great size, was found to grow from a few grammes 

 to 42 lb. in three years, and to double that weight in another year 

 and a half; these scanty data are in fair accord, ^o far as they go, 

 with those for the giant tortoises*. 



* For these and other data, see C. H. Townsend, Growth and age in the giant 

 tortoises of the Galapagos, Zoologica, ix, pp. 459-466, 1931; G. H. Parker, Growth 

 of the loggerhead turtle, Amer. Naturalist, lxvii, pp. 367-373, 1929; Stanley F. 

 Flower, Duration of Life in Animals, in, Reptiles, P.Z.S. (A), 1937, pp. 1-39. 



