Lamarck's hypothesis is no doubt a great help and a great step toward Professor Hering's; it makes a known cause underlie variations, and thus is free from those fatal objections which Professor Mivart and others have brought against the theory of Messrs. Darwin and Wallace; but how does the theory that use develops an organism explain why offspring repeat the organism at all? How does the Lamarckian hypothesis explain the sterility of hybrids, for example? The sterility of hybrids has been always considered one of the great _cruces_ in connection with any theory of Evolution. How again does it explain reversion to long-lost characters and the resumption of feral characteristics? the phenomena of old age? the principle that underlies longevity? the reason why the reproductive system is generally the last to arrive at maturity, and why few further developments take place in any organism after this has been fully developed? the sterility of many animals under captivity? the development in both males and females, under certain circumstances, of the characteristics of the opposite sex? the latency of memory? the unconsciousness with which we develop, and with which instinctive actions are performed? How does any theory advanced either by Lamarck, Mr. Herbert Spencer, or Mr. Darwin explain, or indeed throw light upon these facts until supplemented with the explanation given of them in Life and Habit--for which I must refer the reader to that work itself? People may say what they like about "the experience of the race," {254a} "the registration of experiences continued for numberless generations," {254b} "infinity of experiences," {254c} "lapsed intelligence," &c., but until they make Memory, in the most uncompromising sense of the word, the key to all the phenomena of Heredity, they will get little help to the better understanding of the difficulties above adverted to. Add this to the theory of Buffon, Erasmus Darwin, and Lamarck, and the points which I have above alluded to receive a good deal of "lucidity." But to return to Mr. Romanes: however much he and Mr. Allen may differ about the merits of Mr. Darwin, they were at any rate not long since cordially agreed in vilipending my unhappy self, and are now saying very much what I have been saying for some years past. I do not deny that they are capable witnesses. They will generally see a thing when a certain number of other people have come to do so. I submit that, no matter how grudgingly they give their evidence, the tendency of that evidence is sufficiently clear to show that the opinions put forward in Life and Habit, Evolution, Old and New, and Unconscious Memory, deserve the attention of the reader.