[9] This term is borrowed from the well-known works of Galton on composite photographs, which are scarcely more than twenty years old. Huxley in his book on Hume (Chapter IV.) appears to be the first who introduced it into psychology, as shown by the following passage: “This mental operation may be rendered comprehensible by considering what takes place in the formation of compound photographs—when the images of the faces of six sitters, for example, are each received on the same photographic plate, for a sixth of the time requisite to take one portrait. The final result is that all those points in which the six faces agree are brought out strongly, while all those in which they differ are left vague; and thus what may be termed a generic portrait of the six is produced. Thus our ideas of single complex impressions are incomplete in one way, and those of numerous, more or less similar, complex impressions are incomplete in another way; that is to say, they are generic.... And hence it follows that our ideas of the impressions in question are not, in the strict sense of the word, copies of those impressions; while at the same time they may exist in the mind independently of language.” Romanes employs the word “recept” for “generic images,” as marking their intermediate place between the “percept” which is below, and the “concept” which is above them.
[10] For details see Romanes, Animal Intelligence, Chapters III. and V. As to the probability of their possessing means of communication for assistance in their co-operative labors see below, [Chapter II].
[11] Romanes. Animal Intelligence, Chapter III.
[12] C. Lloyd Morgan. Animal Life and Intelligence, Chapter IX., p. 364.
[13] Houzeau, Etudes sur les facultés mentales des animaux, Vol. II., p. 264 et seq. The same author gives an example of generalisation in bees.
[14] Darwin, The Descent of Man, Vol. I., Chapter III.
[15] Romanes, loc. cit., Chapter XVII.
[16] At the end of the passage in question there is an extraordinary account of the arithmetical powers of a dog which Lubbock explains by “thought reading.” I omit this instance, since we are deliberately rejecting all rare or doubtful cases.
[17] Mental Evolution in Man, Chapter III., p. 58.
[18] J. Sully, The Human Mind, I., 460. The author gives excellent diagrams to represent the difference in the two cases. For reasoning from particular to particular, cf. also J. S. Mill, Logic, II., Chapter III., p. 3; Bradley, Logic, II., Chapter II., p. 2.