296 



AMERICAN TESTUDINATA. 



Part II. 



SECTION XV. 



THE PSYCHOLOGICAL DEVELOPMENT OF TURTLES COMPARED WITH THAT OF THE OTHER 



ORDERS OF REPTILES. 



It is a question of the greatest interest, and one which must arise in the mind 

 of every reader who has entered into the spirit of the First Part of this work, 

 whether the psychological development of animals rises in the same degree as the 

 development of the complication of their structure generally. If this be the case, 

 it follows directly that the rank of the orders expresses at the same time the 

 range of their psychological development. And we think that this is really the 

 case. Now since we have shown that, owing to the complication of their structure, 

 the Turtles are really the highest order among Eeptiles, we must exjDect to find 

 in them also the highest psychological development of the whole class, higher 

 indeed than that of Lizards and Snakes. 



But, to measure the psychological development of animals is one of the most 

 difficult tasks in natural science, since it can only be done by a comjiarison of 

 those functions through which the mental energies are manifested, and the grada- 

 tion and intensity of which are not so easily ascertained as those of other organs. 

 These functions are, the sensations and the motions. 



With reference to the sensations, it cannot be doubted that they stand in 



distinct in the young animal when hatching, more 

 so indeed tlian in Clir. picta, in which, as stated 

 above, I have sometimes seen such a mark when 

 young ; and while it now increases in Chr. Bellii, 

 it disappears entirely, in the two or three following 

 years, in Chr. picta. Then again, in relation to 

 the form, we find that the specific character of the 

 carapace, by which Chr. picta and Chr. Bellii are 

 so easily distinguished when adult, (the large diame- \ 

 ter of tlie hind part of the shield in comparison to 

 its front part, as we meet it in Chr. Bellii, while 

 in Chr. picta both these diameters are nearly 

 equal,) only appears about the seventh year. Thus, 

 we see that in this development there is not a 

 definite and regular series in the appearance of 

 specific, generic, family, and ordinal characters ; a ' 

 specific character may appear, while the family 



character is not yet marked. The young Chrysemys 

 Bellii, when hatching, has really in its forms, which 

 constitute family characters, not much more relation 

 to the family of Emydoida; than a Trionyx, when 

 hatching, while it already exhibits its specific coloring 

 in contradistinction to that nearly allied species, 

 Chr. picta. The idea that an animal, in its develop- 

 ment from the egg, exhibits first, class, then order, 

 then family, then generic, then specific characters, 

 may be true in some cases, but it is certain that in 

 most species this is not the case. On the contrary, 

 I do not hesitate to say that there are many ani- 

 mals which exhibit in their youth the characters 

 of a different family from that to which they really 

 belong when adult. It is evident that if this be 

 the case, the supposed law, above alluded to, is 

 positively denied in nature. 



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