would tend to fall in with the ways which had become traditional in the species. Professor Wesley Mills tells us that a mongrel pup, whose psychical development he carefully watched, showed “extraordinarily rapid” progress when he was introduced to the society of other dogs, and was thus subjected to the influence of canine tradition. How far this influence extends in animal communities--how far it is either a necessary or even an important contributory factor in the development of certain modes of behaviour--is at present in large degree a matter of speculation. And the only justification for speculation in science is that it may open our eyes to modes of influence the range and limits of whose effects may be submitted to the touchstone of careful observation, and, if possible, experiment. In this instance it is rather the indefiniteness of the evidence before us than its absence that stands in the way of any profitable discussion of the problem from the evidential point of view. And this indefiniteness is partly due to the fact that the need of observation is not realized, because this factor in animal behaviour has not been distinguished with sufficient clearness. It is worth while, therefore, to devote a short space to a consideration of the relation of this tradition to instinct and intelligence with a view to the focussing of observation on the facts by which it may be further elucidated. In the first place, it is probable that, as in other modes of animal behaviour, traditional procedure is founded on an instinctive basis. This must be an imitative tendency of the broad follow-my-leader type indicated in the first section of this chapter. And this would afford wide instinctive foundations, which would owe their hereditary character to the fact that, under natural selection, those individuals in the community would survive which fell into line with the adaptive behaviour of their companions, while those which failed in this respect would be eliminated as more or less isolated outsiders, standing apart from the social life. In illustration we may take a hypothetical case, founded, however, upon observation. The Rev. S. J. Whitmee, a missionary in Samoa, believes that the tooth-billed pigeon of these islands (_Didunculus strigirostris_) “has probably been frightened when roosting, or during incubation, by attacks of cats, and has sought safety in the trees. Learning, from frequent repetition of the fright, that the ground is a dangerous place, it has acquired the habit of building, roosting, and feeding on the high trees; and this habit is now operating for the preservation of this interesting bird, which a few years ago was almost extinct.”[104] Now, in this case, the young birds which followed the lead of those who, under experience, had acquired the habit, would stand a better chance of survival than those who, failing to do so, were caught napping on the ground. In further