On the contrary, a lecture "On the Law of Mutual Aid," which was delivered at a Russian Congress of Naturalists, in January 1880, by the well-known zoologist, Professor Kessler, the then Dean of the St. Petersburg University, struck me as throwing a new light on the whole subject. Kessler's idea was, that besides the law of Mutual Struggle there is in Nature the law of Mutual Aid, which, for the success of the struggle for life, and especially for the progressive evolution of the species, is far more important than the law of mutual contest. This suggestion--which was, in reality, nothing but a further development of the ideas expressed by Darwin himself in The Descent of Man--seemed to me so correct and of so great an importance, that since I became acquainted with it (in 1883) I began to collect materials for further developing the idea, which Kessler had only cursorily sketched in his lecture, but had not lived to develop. He died in 1881. 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.