If another objector maintains that the vibrations within the germ as above supposed must be continually crossing and interfering with one another in such a manner as to destroy the continuity of any one series, it may be replied that the vibrations of the light proceeding from the objects that surround us traverse one another by the millions of millions every second yet in no way interfere with one another. Nevertheless, it must be admitted that the difficulties of the theory towards which I suppose Professor Hering to incline are like those of all other theories on the same subject—almost inconceivably great. In “Life and Habit” I did not touch upon these vibrations, knowing nothing about them. Here, then, is one important point of difference, not between the conclusions arrived at, but between the aim and scope of the work that Professor Hering and I severally attempted. Another difference consists in the points at which we have left off. Professor Hering, having established his main thesis, is content. I, on the other hand, went on to maintain that if vigour was due to memory, want of vigour was due to want of memory. Thus I was led to connect memory with the phenomena of hybridism and of old age; to show that the sterility of certain animals under domestication is only a phase of, and of a piece with, the very common sterility of hybrids—phenomena which at first sight have no connection either with each other or with memory, but the connection between which will never be lost sight of by those who have once laid hold of it. I also pointed out how exactly the phenomena of development agreed with those of the abeyance and recurrence of memory, and the rationale of the fact that puberty in so many animals and plants comes about the end of development. The principle underlying longevity follows as a matter of course. I have no idea how far Professor Hering would agree with me in the position I have taken in respect of these phenomena, but there is nothing in the above at variance with his lecture. Another matter on which Professor Hering has not touched is the bearing of his theory on that view of evolution which is now commonly accepted. It is plain he accepts evolution, but it does not appear that he sees how fatal his theory is to any view of evolution except a teleological one—the purpose residing within the animal and not without it. There is, however, nothing in his lecture to indicate that he does not see this.