which all young mammals instinctively indulge are obviously adapted to this end, as well as to enable them to acquire fit corporal traits, as is beautifully illustrated by the differences in the sports of kittens and puppies.
We constantly meet passages in the writings of various authors, wherein they attribute this or that mental change in lower animals or men to "centuries of domestication," or "centuries of civilization," or "to centuries" of this or that change in the environment, the implication being that acquired mental traits are transmitted and accumulated, for otherwise the word "century" would not be applied to creatures whose lives are much shorter. The evidence, however, is overwhelmingly against such a supposition. Our various breeds of house dogs, for example, have all lived and evolved under much the same conditions, and therefore if acquired mental traits are transmissible, should exhibit similar qualities. The difference between the dispositions of bulldogs and lapdogs, for instance, <3an only have arisen (1) through artificial selection, or (2) through differences in individually acquired (and not transmissible) traits; the latter being secondary to physical conformation, which in the bulldog must tend, through success in conflict, to produce a bold, resolute, and confident spirit, and in the lapdog a spirit much the reverse. And here I may remark, that in all animals capable of acquiring mental traits, the character of these traits must in every case be profoundly influenced by the physical conformation. À priori, very many of the traits exhibited by domesticated animals must be acquired, not inborn, since they are mentally so malleable as to be capable of domestication, of adapting themselves to an " abnormal " environment; à posteriori, these traits are proved to be acquired and non-inheritable, since every one of our domesticated animals,—dogs, cats, horses, sheep, goats, pigs, poultry, &c.,—when relieved of
