The last of Butler's biological writings is the Essay, "THE DEADLOCK IN DARWINISM," containing much valuable criticism on Wallace and Weismann. It is in allusion to the misnomer of Wallace's book, "Darwinism," that he introduces the term "Wallaceism" {0d} for a theory of descent that excludes the transmission of acquired characters. This was, indeed, the chief factor that led Charles Darwin to invent his hypothesis of pangenesis, which, unacceptable as it has proved, had far more to recommend it as a formal hypothesis than the equally formal germ-plasm hypothesis of Weismann.

The chief difficulty in accepting the main theses of Butler and Hering is one familiar to every biologist, and not at all difficult to understand by the layman. Everyone knows that the complicated beings that we term "Animals" and "Plants," consist of a number of more or less individualised units, the cells, each analogous to a simpler being, a Protist--save in so far as the character of the cell unit of the Higher being is modified in accordance with the part it plays in that complex being as a whole. Most people, too, are familiar with the fact that the complex being starts as a single cell, separated from its parent; or, where bisexual reproduction occurs, from a cell due to the fusion of two cells, each detached from its parent. Such cells are called "Germ-cells." The germ-cell, whether of single or of dual origin, starts by dividing repeatedly, so as to form the PRIMARY EMBRYONIC CELLS, a complex mass of cells, at first essentially similar, which, however, as they go on multiplying, undergo differentiations and migrations, losing their simplicity as they do so. Those cells that are modified to take part in the proper work of the whole are called tissue-cells. In virtue of their activities, their growth and reproductive power are limited- -much more in Animals than in Plants, in Higher than in Lower beings. It is these tissues, or some of them, that receive the impressions from the outside which leave the imprint of memory. Other cells, which may be closely associated into a continuous organ, or more or less surrounded by tissue-cells, whose part it is to nourish them, are called "secondary embryonic cells," or "germ-cells." The germ- cells may be differentiated in the young organism at a very early stage, but in Plants they are separated at a much later date from the less isolated embryonic regions that provide for the Plant's branching; in all cases we find embryonic and germ-cells screened from the life processes of the complex organism, or taking no very obvious part in it, save to form new tissues or new organs, notably in Plants.

Again, in ourselves, and to a greater or less extent in all Animals, we find a system of special tissues set apart for the reception and storage of impressions from the outer world, and for guiding the other organs in their appropriate responses--the "Nervous System"; and when this system is ill-developed or out of gear the remaining organs work badly from lack of proper skilled guidance and co- ordination. How can we, then, speak of "memory" in a germ-cell which has been screened from the experiences of the organism, which is too simple in structure to realise them if it were exposed to them? My own answer is that we cannot form any theory on the subject, the only question is whether we have any right to INFER this "memory" from the BEHAVIOUR of living beings; and Butler, like Hering, Haeckel, and some more modern authors, has shown that the inference is a very strong presumption. Again, it is easy to over-value such complex instruments as we possess. The possessor of an up-to-date camera, well instructed in the function and manipulation of every part, but ignorant of all optics save a hand-to-mouth knowledge of the properties of his own lens, might say that a priori no picture could be taken with a cigar-box perforated by a pin-hole; and our ignorance of the mechanism of the Psychology of any organism is greater by many times than that of my supposed photographer. We know that Plants are able to do many things that can only be accounted for by ascribing to them a "psyche," and these co-ordinated enough to satisfy their needs; and yet they possess no central organ comparable to the brain, no highly specialised system for intercommunication like our nerve trunks and fibres. As Oscar Hertwig says, we are as ignorant of the mechanism of the development of the individual as we are of that of hereditary transmission of acquired characters, and the absence of such mechanism in either case is no reason for rejecting the proven fact.

However, the relations of germ and body just described led Jager, Nussbaum, Galton, Lankester, and, above all, Weismann, to the view that the germ-cells or "stirp" (Galton) were IN the body, but not OF it. Indeed, in the body and out of it, whether as reproductive cells set free, or in the developing embryo, they are regarded as forming one continuous homogeneity, in contrast to the differentiation of the body; and it is to these cells, regarded as a continuum, that the terms stirp, germ-plasm, are especially applied. Yet on this view, so eagerly advocated by its supporters, we have to substitute for the hypothesis of memory, which they declare to have no real meaning here, the far more fantastic hypotheses of Weismann: by these they explain the process of differentiation in the young embryo into new germ and body; and in the young body the differentiation of its cells, each in due time and place, into the varied tissue cells and organs. Such views might perhaps be acceptable if it could be shown that over each cell-division there presided a wise all-guiding genie of transcending intellect, to which Clerk-Maxwell's sorting demons were mere infants. Yet these views have so enchanted many distinguished biologists, that in dealing with the subject they have actually ignored the existence of equally able workers who hesitate to share the extremest of their views. The phenomenon is one well known in hypnotic practice. So long as the non-Weismannians deal with matters outside this discussion, their existence and their work is rated at its just value; but any work of theirs on this point so affects the orthodox Weismannite (whether he accept this label or reject it does not matter), that for the time being their existence and the good work they have done are alike non-existent. {0e}

Butler founded no school, and wished to found none. He desired that what was true in his work should prevail, and he looked forward calmly to the time when the recognition of that truth and of his share in advancing it should give him in the lives of others that immortality for which alone he craved.

Lamarckian views have never lacked defenders here and in America. Of the English, Herbert Spencer, who however, was averse to the vitalistic attitude, Vines and Henslow among botanists, Cunningham among zoologists, have always resisted Weismannism; but, I think, none of these was distinctly influenced by Hering and Butler. In America the majority of the great school of palaeontologists have been strong Lamarckians, notably Cope, who has pointed out, moreover, that the transformations of energy in living beings are peculiar to them.

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 Rontgen'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."

It will be seen that I express doubts as to the validity of Hering's invocation of molecular vibrations as the mechanism of memory, and suggest as an alternative rhythmic chemical changes. This view has recently been put forth in detail by J. J. Cunningham in his essay on the "Hormone {0f} Theory of Heredity," in the Archiv fur Entwicklungsmechanik (1909), but I have failed to note any direct effect of my essay on the trend of biological thought.

Among post-Darwinian controversies the one that has latterly assumed the greatest prominence is that of the relative importance of small variations in the way of more or less "fluctuations," and of "discontinuous variations," or "mutations," as De Vries has called them. Darwin, in the first four editions of the "Origin of Species," attached more importance to the latter than in subsequent editions; he was swayed in his attitude, as is well known, by an article of the physicist, Fleeming Jenkin, which appeared in the North British Review. The mathematics of this article were unimpeachable, but they were founded on the assumption that exceptional variations would only occur in single individuals, which is, indeed, often the case among those domesticated races on which Darwin especially studied the phenomena of variation. Darwin was no mathematician or physicist, and we are told in his biography that he regarded every tool-shop rule or optician's thermometer as an instrument of precision: so he appears to have regarded Fleeming Jenkin's demonstration as a mathematical deduction which he was bound to accept without criticism.

Mr. William Bateson, late Professor of Biology in the University of Cambridge, as early as 1894 laid great stress on the importance of discontinuous variations, collecting and collating the known facts in his "Materials for the Study of Variations"; but this important work,