This involves the older "Darwinism" and the theory of Lamarck, according to which the modification of living forms has been effected mainly through the needs of the living forms themselves, which vary with varying conditions--the survival of the fittest (which, as I see Mr. H. B. Baildon has just said, "sometimes comes to mean merely the survival of the survivors" {181c}) being taken as a matter of course. According to this view of evolution, there is a remarkable analogy between the development of living organs, or tools, and that of those organs or tools external to the body which has been so rapid during the last few thousand years. Animals and plants, according to Professor Hering, are guided throughout their development, and preserve the due order in each step they take, through memory of the course they took on past occasions when in the persons of their ancestors. I am afraid I have already too often said that if this memory remains for long periods together latent and without effect, it is because the vibrations of the molecular substance of the body which are its supposed explanation are during these periods too feeble to generate action, until they are augmented in force through an accession of similar vibrations issuing from exterior objects; or, in other words, until recollection is stimulated by a return of the associated ideas. On this the internal agitation becomes so much enhanced, that equilibrium is visibly disturbed, and the action ensues which is proper to the vibrations of the particular substance under the particular conditions. This, at least, is what I suppose Professor Hering to intend. Leaving the explanation of memory on one side, and confining ourselves to the fact of memory only, a caterpillar on being just hatched is supposed, according to this theory, to lose its memory of the time it was in the egg, and to be stimulated by an intense but unconscious recollection of the action taken by its ancestors when they were first hatched. It is guided in the course it takes by the experience it can thus command. Each step it takes recalls a new recollection, and thus it goes through a development as a performer performs a piece of music, each bar leading his recollection to the bar that should next follow. In Life and Habit will be found examples of the manner in which this view solves a number of difficulties for the explanation of which the leading men of science express themselves at a loss. The following from Professor Huxley's recent work upon the crayfish may serve for an example. Professor Huxley writes:--