Chap. I. 



GROWTH OF TURTLES. 



203 



ages, and the simplicity of their fonns. As a roundisli form is an attribute 

 of the young, which we may trace throughout the animal kingdom, so also 

 has simplicity of ornamentation, particularly of color, been considered as charac- 

 teristic of the younger age. Most Birds furnish examples of this law, in their 

 monotonous gray plumage at the time of hatching, when contrasted with the 

 beauty, gayety, and variety of colors in the adult. But in Eeptiles this law is not 

 so obvious, and there are even very striking exceptions, if the opposite is not 

 actually to be considered as the rule. A Boa constrictor, a striped Snake, a 

 Rattlesnake, when hatching, show the same purity of colors as the adult, or even 

 a greater brilliancy. The same seems to be the case with Turtles, if we compare, 

 for instance, the beautiful network of yellow lines in Graptemys Lesueurii and 

 geographica, when hatching, with the pale colors of the adult. Still, the law 

 mentioned above is maintained, at least thus far, that few young Turtles have 

 really purer colors than the adults. Yet there are some, which in middle life 

 are more brilliant than either in their earlier years or in old age. This is, for 

 instance, the case with Ptychem^'s concinna, (E. floridana,) and rugosa, (E. rubri- 

 ventris,) and with Emys Meleagris, (Cistudo Blandingii.) From all those instances 

 which I have investigated more thoroughly, it may be inferred that the fading 

 of the colors iu adult specimens is either owing to the thickness of the grayish 

 epidermis, which thus obscures the Malpighian layer, in which the color resides, 

 or to external mechanical influences which injure the smoothness of the epidermis. 

 In order to illustrate this subject more fully, I add in a note moi'e minute 

 details relating to the development of Chrj'semys picta, not only as far as its 

 form is concerned, but also respecting its colors. A large series of specimens of 

 all ages, from the youngest, just hatched, to the adult, including very old ones, 

 collected in the same season of the 3^ear and at the same time, enables me to 

 present this sketch.' I have selected this species to illustrate the changes which 



' When comparing young specimens of our most 

 common Turtles with adult ones, our Emys picta for 

 instance, when just hatched, there are three points 

 ■ivhirh strike us at first sight. A large, full head, 

 a circular, flat carapace, and a long tail, vertically 

 compressed. The head, at first almost a regular ball 

 with three prominences, the two large eyes and the 

 nose, becomes in more advanced age more and more 

 pyramidal : it lias in the adult four distinct sides, a 

 very flat upjicr surface, two lateral surfaces, which 

 are slightly bent, and a flat under surface. T?ut it 

 is remarkable, that in Emys concentrica, and also, 

 though in a less degree, in the type of Kniys floridana. 



that youthful form of the head continues throughout 

 life. This is more remarkable still, if we remember 

 that just these species are the most aquatic among 

 Emydoida^, and further that our young Emys picta 

 is itself much more aquatic in its habits, during the 

 first years of its life, than it is in later life. In 

 relation to the changes of the forms of the carapace, 

 I have presented these in the shape of a table, in 

 which the dift'erences arising during the growth, in 

 the relative proportions of the ditlerent diameters 

 of the body, may be seen at a glance. See p. 292. 

 Thus we may say that this Emj-s, for the first 

 four or six years of its life, has the shape of the 



