now become rare and valuable, at the time excited so little interest as to be 'remaindered' within a very few years after publication.

In 1901 Hugo De Vries, Professor of Botany in the University of Amsterdam, published "Die Mutationstheorie," wherein he showed that mutations or discontinuous variations in various directions may appear simultaneously in many individuals, and in various directions. In the gardener's phrase, the species may take to sporting in various directions at the same time, and each sport may be represented by numerous specimens.

De Vries shows the probability that species go on for long periods showing only fluctuations, and then suddenly take to sporting in the way described, short periods of mutation alternating with long intervals of relative constancy. It is to mutations that De Vries and his school, as well as Luther Burbank, the great former of new fruit- and flower-plants, look for those variations which form the material of Natural Selection. In "God the Known and God the Unknown," which appeared in the Examiner (May, June, and July), 1879, but though then revised was only published posthumously in 1909, Butler anticipates this distinction:-

"Under these circumstances organism must act in one or other of these two ways: it must either change slowly and continuously with the surroundings, paying cash for everything, meeting the smallest change with a corresponding modification, so far as is found convenient, or it must put off change as long as possible, and then make larger and more sweeping changes.

"Both these courses are the same in principle, the difference being one of scale, and the one being a miniature of the other, as a ripple is an Atlantic wave in little; both have their advantages and disadvantages, so that most organisms will take the one course for one set of things and the other for another. They will deal promptly with things which they can get at easily, and which lie more upon the surface; THOSE, HOWEVER, WHICH ARE MORE TROUBLESOME TO REACH, AND LIE DEEPER, WILL BE HANDLED UPON MORE CATACLYSMIC PRINCIPLES, BEING ALLOWED LONGER PERIODS OF REPOSE FOLLOWED BY SHORT PERIODS OF GREATER ACTIVITY . . . it may be questioned whether what is called a sport is not the organic expression of discontent which has been long felt, but which has not been attended to, nor been met step by step by as much small remedial modification as was found practicable: so that when a change does come it comes by way of revolution. Or, again (only that it comes to much the same thing), it may be compared to one of those happy thoughts which sometimes come to us unbidden after we have been thinking for a long time what to do, or how to arrange our ideas, and have yet been unable to come to any conclusion" (pp. 14, 15). {0g}

We come to another order of mind in Hans Driesch. At the time he began his work biologists were largely busy in a region indicated by Darwin, and roughly mapped out by Haeckel--that of phylogeny. From the facts of development of the individual, from the comparison of fossils in successive strata, they set to work at the construction of pedigrees, and strove to bring into line the principles of classification with the more or less hypothetical "stemtrees." Driesch considered this futile, since we never could reconstruct from such evidence anything certain in the history of the past. He therefore asserted that a more complete knowledge of the physics and chemistry of the organic world might give a scientific explanation of the phenomena, and maintained that the proper work of the biologist was to deepen our knowledge in these respects. He embodied his views, seeking the explanation on this track, filling up gaps and tracing projected roads along lines of probable truth in his "Analytische Theorie der organische Entwicklung." But his own work convinced him of the hopelessness of the task he had undertaken, and he has become as strenuous a vitalist as Butler. The most complete statement of his present views is to be found in "The Philosophy of Life" (1908-9), being the Giffold Lectures for 1907-8. Herein he postulates a quality ("psychoid") in all living beings, directing energy and matter for the purpose of the organism, and to this he applies the Aristotelian designation "Entelechy." The question of the transmission of acquired characters is regarded as doubtful, and he does not emphasise--if he accepts--the doctrine of continuous personality. His early youthful impatience with descent theories and hypotheses has, however, disappeared.

In the next work the influence of Hering and Butler is definitely present and recognised. In 1906 Signor Eugenio Rignano, an engineer keenly interested in all branches of science, and a little later the founder of the international review, Rivista di Scienza (now simply called Scientia), published in French a volume entitled "Sur la transmissibilite des Caracteres acquis--Hypothese d'un Centro- epigenese." Into the details of the author's work we will not enter fully. Suffice it to know that he accepts the Hering-Butler theory, and makes a distinct advance on Hering's rather crude hypothesis of persistent vibrations by suggesting that the remembering centres store slightly different forms of energy, to give out energy of the same kind as they have received, like electrical accumulators. The last chapter, "Le Phenomene mnemonique et le Phenomene vital," is frankly based on Hering.

In "The Lesson of Evolution" (1907, posthumous, and only published for private circulation) Frederick Wollaston Hutton, F.R.S., late Professor of Biology and Geology, first at Dunedin and after at Christchurch, New Zealand, puts forward a strongly vitalistic view, and adopts Hering's teaching. After stating this he adds, "The same idea of heredity being due to unconscious memory was advocated by Mr. Samuel Butler in his "Life and Habit."

Dr. James Mark Baldwin, Stuart Professor of Psychology in Princeton University, U.S.A., called attention early in the 90's to a reaction characteristic of all living beings, which he terms the "Circular Reaction." We take his most recent account of this from his "Development and Evolution" (1902):- {0h}

"The general fact is that the organism reacts by concentration upon the locality stimulated for the CONTINUANCE of the conditions, movements, stimulations, WHICH ARE VITALLY BENEFICIAL, and for the cessation of the conditions, movements, stimulations WHICH ARE VITALLY DEPRESSING."

This amounts to saying in the terminology of Jenning (see below) that the living organism alters its "physiological states" either for its direct benefit, or for its indirect benefit in the reduction of harmful conditions.

Again:-

"This form of concentration of energy on stimulated localities, with the resulting renewal through movement of conditions that are pleasure-giving and beneficial, and the consequent repetition of the movements is called 'circular reaction.'"

Of course, the inhibition of such movements as would be painful on repetition is merely the negative case of the circular reaction. We must not put too much of our own ideas into the author's mind; he nowhere says explicitly that the animal or plant shows its sense and does this because it likes the one thing and wants it repeated, or dislikes the other and stops its repetition, as Butler would have said. Baldwin is very strong in insisting that no full explanation can be given of living processes, any more than of history, on purely chemico-physical grounds.

The same view is put differently and independently by H. S. Jennings, {0i} who started his investigations of living Protista, the simplest of living beings, with the idea that only accurate and ample observation was needed to enable us to explain all their activities on a mechanical basis, and devised ingenious models of protoplastic movements. He was led, like Driesch, to renounce such efforts as illusory, and has come to the conviction that in the behaviour of these lowly beings there is a purposive and a tentative character--a method of "trial and error"--that can only be interpreted by the invocation of psychology. He points out that after stimulation the "state" of the organism may be altered, so that the response to the same stimulus on repetition is other. Or, as he puts it, the first stimulus has caused the organism to pass into a new "physiological state." As the change of state from what we may call the "primary indifferent state" is advantageous to the organism, we may regard this as equivalent to the doctrine of the "circular reaction," and also as containing the essence of Semon's doctrine of "engrams" or imprints which we are about to consider. We cite one passage which for audacity of thought (underlying, it is true, most guarded expression) may well compare with many of the boldest flights in "Life and Habit":-

"It may be noted that regulation in the manner we have set forth is what, in the behaviour of higher organisms, at least, is called intelligence [the examples have been taken from Protista, Corals, and the Lowest Worms]. If the same method of regulation is found in other fields, there is no reason for refusing to compare the action to intelligence. Comparison of the regulatory processes that are shown in internal physiological changes and in regeneration to intelligence seems to be looked upon sometimes as heretical and unscientific. Yet intelligence is a name applied to processes that actually exist in the regulation of movements, and there is, a priori, no reason why similar processes should not occur in regulation in other fields. When we analyse regulation objectively there seems indeed reason to think that the processes are of the same character in behaviour as elsewhere. If the term intelligence be reserved for the subjective accompaniments of such regulation, then of course we have no direct knowledge of its existence in any of the fields of regulation outside of the self, and in the self perhaps only in behaviour. But in a purely objective consideration there seems no reason to suppose that regulation in behaviour (intelligence) is of a fundamentally different character from regulation elsewhere." ("Method of Regulation," p. 492.)

Jennings makes no mention of questions of the theory of heredity. He has made some experiments on the transmission of an acquired character in Protozoa; but it was a mutilation-character, which is, as has been often shown, {0j} not to the point.

One of the most obvious criticisms of Hering's exposition is based upon the extended use he makes of the word "Memory": this he had foreseen and deprecated.

"We have a perfect right," he says, "to extend our conception of memory so as to make it embrace involuntary [and also unconscious] reproductions of sensations, ideas, perceptions, and efforts; but we find, on having done so, that we have so far enlarged her boundaries