BRITISH WARBLERS
The sexual and parental instinct and the instinct of pugnacity all have their corresponding emotion, which is supposed to have a definite part to play in furthering the life of the individual. I do not for a moment deny that such a supposition may be correct, but there are many facts which are at variance first with this and then with that interpretation, if we are to regard the correlation of this instinctive performance with that emotional expression as definitely fixed and exclusive of cross-correlation, and very much that we do not in the least understand. For instance, there is the interpretation placed upon the emotion which accompanies the parental instinct. Many species, when their nest or young are interfered with, perform in a manner which, without an undue stretching of the imagination, might be regarded as a simulation of helplessness, and their behaviour thus appears to be purposive. Instances are given in the life of the Lesser Whitethroat and some remarks added which, though they do not carry us much further towards a solution, serve to show the difficulties in the path of interpretation. One might go on discussing this particular aspect of behaviour interminably. Here I will only draw attention to one feature of all emotional manifestation, namely, the similarity in the type and intensity of the response at different emotional periods. I am fully aware that in using the term "similarity" I lay myself open to criticism, on the ground that our perceptual powers are too feeble to differentiate between such subtle manifestations. But while I am quite prepared to admit the dulness of our perceptual powers when compared with those of the lower animals, I nevertheless hesitate to attribute the observed similarity wholly to this fact; in other words, I believe that it is really there and has to be reckoned with. Professor Lloyd Morgan holds that the differentiation of emotion from a common base is a more fruitful conception than the mode of synthesis proposed by Dr. McDougall. Similarity, on his view, becomes more explicable; for if it can be shown that there is a strong probability of some specific type of behaviour serving a double or a treble purpose, so much
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