In one point only I could not entirely endorse Kessler’s views.  Kessler alluded to “parental feeling” and care for progeny (see below, Chapter I) as to the source of mutual inclinations in animals.  However, to determine how far these two feelings have really been at work in the evolution of sociable instincts, and how far other instincts have been at work in the same direction, seems to me a quite distinct and a very wide question, which we hardly can discuss yet.  It will be only after we have well established the facts of mutual aid in different classes of animals, and their importance for evolution, that we shall be able to study what belongs in the evolution of sociable feelings, to parental feelings, and what to sociability proper—­the latter having evidently its origin at the earliest stages of the evolution of the animal world, perhaps even at the “colony-stages.”  I consequently directed my chief attention to establishing first of all, the importance of the Mutual Aid factor of evolution, leaving to ulterior research the task of discovering the origin of the Mutual Aid instinct in Nature.

The importance of the Mutual Aid factor—­“if its generality could only be demonstrated”—­did not escape the naturalist’s genius so manifest in Goethe.  When Eckermann told once to Goethe—­ it was in 1827—­that two little wren-fledglings, which had run away from him, were found by him next day in the nest of robin redbreasts (Rothkehlchen), which fed the little ones, together with their own youngsters, Goethe grew quite excited about this fact.  He saw in it a confirmation of his pantheistic views, and said:—­“If it be true that this feeding of a stranger goes through all Nature as something having the character of a general law—­then many an enigma would be solved.  “He returned to this matter on the next day, and most earnestly entreated Eckermann (who was, as is known, a zoologist) to make a special study of the subject, adding that he would surely come “to quite invaluable treasuries of results” (Gesprache, edition of 1848, vol. iii. pp. 219, 221).  Unfortunately, this study was never made, although it is very possible that Brehm, who has accumulated in his works such rich materials relative to mutual aid among animals, might have been inspired by Goethe’s remark.

Several works of importance were published in the years 1872-1886, dealing with the intelligence and the mental life of animals (they are mentioned in a footnote in Chapter I of this book), and three of them dealt more especially with the subject under consideration; namely, Les Societes animales, by Espinas (Paris, 1877); La Lutte pour l’existence et l’association pout la lutte, a lecture by J.L.  Lanessan (April 1881); and Louis Buchner’s book, Liebe und Liebes-Leben in der Thierwelt, of which the first edition appeared in 1882 or 1883, and a second, much enlarged, in 1885.  But excellent though each of these works is, they leave ample room for a work in which Mutual Aid would