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friend Mr. Marshall has asked me to make any alterations or corrections in his paper. I find, however, that I so entirely agree with the whole of the argument that I have merely added a few confirmatory notes to certain passages in the paper, which are in each case marked by a number.

1 H.W. Bates, in his classical paper, also used the term mimicry in the wider sense employed by W.L. Distant. The majority of naturalists have since followed A.R. Wallace in keeping Protective and Aggressive Resemblance distinct from Mimicry—a course which appears to be convenient, inasmuch as the distinction in terms corresponds to a real distinction in the modes of defence. In the former, an animal resembles an object which is of no interest to its enemy, and in so doing becomes concealed; in the latter, an animal resembles an object which its enemy knows well and fears or dislikes, and in so doing becomes conspicuous. Other superficial resemblances—such as those produced by protective resemblances in common, warning colours in common (Müllerian mimicry), and functions in common (analogical or adaptive resemblances of Darwin)—are excluded from mimicry as here defined.

2 See the discussion on "Organic Selection," reported in 'Science,' N.S. vol. vi. No. 146, Oct. 15, 1897, where this view was sustained.

3 Probably most evolutionists would hesitate before committing themselves to such a conclusion. Highly intelligent animals, such as birds, crouch and hide when very young at every unusual sound. This action is performed instinctively and unintelligently, and is apparently an automatic response to stimulus. When the stimulus has been repeated, and no danger is apparent, the young birds cease to crouch. We are not justified in considering that their intelligence has done more than enable them to inhibit an unnecessary response. There is no reason to think that they have any understanding of the meaning of the response itself. See Lloyd Morgan's 'Habit and Instinct' (London, 1896).

4 It should be remembered that the structure and colouring are themselves made up of many complex factors, all of which must co-operate if the mimetic or protective resemblance is to be effective. See Linnean Soc. Journ., Zool., vol. xxvi. pp. 576–578.