no. 2382. SEXUAL DIFFERENCES IN COLORATION— BLAKE. 467 



differences in two or three species mentioned in the first part of this 

 paper, no difference in coloration between the sexes seems to have 

 been recorded in any member of the Chclonia. This is undoubtedly 

 due to the fact that practically all collections of turtles consist chiefly 

 of alcoholic material. The examination of series of such specimens is 

 much less convenient than that of skins; the specimens are often 

 badly distorted or have the members drawn under the shell; and the 

 colors are poorly preserved, although the distribution of the mark- 

 ings can usually be made out satisfactorily. It is somewhat remark- 

 able that Agassiz, who had "thousands" 6 of living specimens of 

 turtles of different species under observation in his yard, apparently 

 failed to distinguish these differences, although he noted 7 sexual 

 differences in the form of the shield, the length of the tail, and the 

 scalation of the legs in the Kinosternidae. 



In 1905, in a report of a meeting of the American Society of Zoolo- 

 gists, R. M. Yerkes 8 published the preliminary results of his study of 

 the spotted turtle, in the following words: 



1. The young of this species of tortoise usually have a single yellow spot on each 

 plate of the carapace except the marginals. With age the number of spots increases; 

 they appear on the marginal plates also, and their arrangement becomes irregular. 



2. The epidermal layer is transparent immediately over the mass of yellow pigment 

 n the outer bony layer, hence, window-like regions in the outer portion of the shell. 



3. Although the females are slightly smaller than the males they usually have 

 about 15 per cent more spots on the carapace. The average number for the males is 

 60, for the females 69. This would seem to indicate that the brightly colored spots 

 serve as both sex and species marks. Probably they serve to render the females 

 conspicuous. 



4. Statistics indicate a greater number of spots on the left side of the carapace than 

 on the right in both males and females. It is possible that this is to be correlated 

 with right-handedness and right-eyedness. 



Professor Yerkes informs me that these conclusions were based on 

 the examination of several hundred specimens, and that several years 

 ago all his data were turned over to Dr. C. B. Davenport for elabora- 

 tion, but that nothing further has been published. (Doctor Daven- 

 port writes me that Professor Yerkes' manuscript has been mislaid.) 

 In the absence of this detailed information it is impossible to assign 

 much weight to the possible correlations suggested in his third and 

 fourth paragraphs. His suggestion that the slightly greater average 

 number of spots found on the females in his series serves as a sex- 

 distinguishing character in nature is rendered very improbable when 

 the great variability of the spotting in both sexes is considered. 



Agassiz's description * of the newly hatched young of this species 

 agrees with that of Yerkes: " When hatched, there is but a single dot 



« Contr. Nat. Hist. U. S., vol. 1, p. 252, footnote, 1857. 



' Idem, p. 419. 



8 Science, new ser., vol. 21, p. 386, 1905. 



» Contr. Nat. Hist. U. S., vol. 1, p. 443,51857. 



