Page:Mind (Old Series) Volume 9.djvu/306

 294 G. J. EOMANES'S MENTAL EVOLUTION IN ANIMALS. ' Neurility '. ' Neurility ' is formed by the confluence of ' Discri- mination ' and ' Conductility,' which have their root in ' Excita- bility'. On the side of Intellect, from a branch representing ' Sensation ' (which springs from the stem) a branch representing 'Perception' is given off; from 'Perception,' 'Imagination' is represented as originating; from 'Imagination,' 'Abstraction'. On the side of Emotion, a branch representing ' Preservation of Self ' and ' of Species ' springs from the stem and gives off a branch the lower part of which represents the beginning of 'Social Emotion'. The names of groups of animals are placed in a column that stands for 'the Psychological Scale'. Opposite these names in two other columns we find the ' Pro- ducts of Intellectual Development ' and ' Products of Emotional Development ' characteristic of each group of animals. The levels drawn across the diagram at equal intervals are intended to represent degrees of elaboration of faculty. The author points out the sufficiently obvious defects of such a diagram that it does not adequately express the transitions that there are in nature from one stage of intelligence to another, and that the division of mind into "faculties" is essentially artificial. But there is another defect which he has not pointed out. The development of mind is represented as proceeding only in a single line. For the branching structure can only represent the division of a single mind at each of its stages into faculties, not the divergence of different types of mind. Nothing is said as to the possibility that at the same level of general intelligence there may be essentially different mental types, dependent, for ex- ample, on different degrees of acuteness of the senses, and dif- ferent ratios of their degrees of acuteness to one another. For anything the diagram tells us and the same thing may be said of the whole book there might be no differences between minds except differences of position in serial order. But if minds have been evolved, we should expect them to fall into groups having the peculiarities pointed out by Darwin as characteristic of all groups that have originated by evolution. And the evolution of existing types of animal intelligence, as well as of existing types of animal organisation, ought to be shown by a genealogical tree, not by a structure that cannot represent the growth of more than one type, either of mind or of organisation. If the con- struction of such a genealogical tree is at present impossible, it might at least have been pointed to as the ideal of a science of comparative psychology. The definitions of the "faculties " are not quite so clear as is to be desired. This is perhaps comparatively unimportant ; for it might be maintained that the distinctions expressed by the terms Sensa- tion, Perception, Imagination, Abstraction, &c., have to such an extent become part of common thought that they may be applied with at least approximate accuracy by a good observer without the aid of strict definitions. But the more special terms that are