We have already adverted to Haeckel’s acceptance and development of Hering’s ideas in his “Perigenese der Plastidule.” Oscar Hertwig has been a consistent Lamarckian, like Yves Delage of the Sorbonne, and these occupy pre-eminent positions not only as observers, but as discriminating theorists and historians of the recent progress of biology. We may also cite as a Lamarckian—of a sort—Felix Le Dantec, the leader of the chemico-physical school of the present day. But we must seek elsewhere for special attention to the points which Butler regarded as the essentials of “Life and Habit.” In 1893 Henry P. Orr, Professor of Biology in the University of Louisiana, published a little book entitled “A Theory of Heredity.” Herein he insists on the nervous control of the whole body, and on the transmission to the reproductive cells of such stimuli, received by the body, as will guide them on their path until they shall have acquired adequate experience of their own in the new body they have formed. I have found the name of neither Butler nor Hering, but the treatment is essentially on their lines, and is both clear and interesting. In 1896 I wrote an essay on “The Fundamental Principles of Heredity,” primarily directed to the man in the street. This, after being held over for more than a year by one leading review, was “declined with regret,” and again after some weeks met the same fate from another editor. It appeared in the pages of “Natural Science” for October, 1897, and in the “Biologisches Centralblatt” for the same year. I reproduce its closing paragraph:— “This theory [Hering-Butler’s] has, indeed, a tentative character, and lacks symmetrical completeness, but is the more welcome as not aiming at the impossible. A whole series of phenomena in organic beings are correlated under the term of _memory_, _conscious and unconscious_, _patent and latent_. . . . Of the order of unconscious memory, latent till the arrival of the appropriate stimulus, is all the co-operative growth and work of the organism, including its development from the reproductive cells. Concerning the _modus operandi_ we know nothing: the phenomena may be due, as Hering suggests, to molecular vibrations, which must be at least as distinct from ordinary physical disturbances as Röntgen’s rays are from ordinary light; or it may be correlated, as we ourselves are inclined to think, with complex chemical changes in an intricate but orderly succession. For the present, at least, the problem of heredity can only be elucidated by the light of mental, and not material processes.”