CHIFF-CHAFF
Although a critical investigation of the complex and divergent activities of the lower animals lends so little support to this theory, it reveals abundant evidence of a law of uniformity extending to all the varied incidents of the lives of the different individuals of the same species, the magnitude and importance of which, so I am inclined to believe, has been obscured by an incessant quest for variation. It is only when we carefully consider the conditions of existence of most species, and understand how favourable those conditions are to any innate modifiability, that we can appreciate the full significance of this law. So favourable, indeed, are they that it has often seemed to me a remarkable fact, and one very difficult of explanation, that individuality is not of frequent and persistent occurrence. Let us take the case of the Chiff-chaff. After reading of the way in which it examines and joins in the various disturbances around, the manner in which the breeding area is fixed and adhered to, the choice of a certain tree as headquarters, and the systematic working towards the boundaries, culminating in a combat or game with its neighbours, no one, I imagine, will deny the variety of its activities nor the complicated movements involved in such activities; but, in addition, this bird possesses vigour in excess of its immediate needs in a greater degree than many other species, resulting in a pronounced restless energy and ceaseless activity. In such an existence as this we must believe that opportunities for modification will constantly arise, yet apparently no individual attempt is made to depart from the rules of the species, for we find that, in so far as the systematic study of different members of the same species enables us to judge, all these activities, both simple and complex, are similarly performed under the same appropriate circumstances by all the individuals of the same species.
And pursuing the subject somewhat further, if we not only accept variation as an established fact, but look upon intelligence as the principal factor, as it is so regarded by
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