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individuals take place through the action of the environment, he will not admit that these changes are inherited! Yet he believes in changes in breeds of domestic animals through "selection." How can selection act, if there is no inherent force to initiate the change? If individual peculiarities are inherited, then it is quite natural that a pointer puppy should point; but if they are not, why should he not accidentally vary in some other direction? There must be some internal force rendering variation possible, or the breeder might select for ever without producing any effect. Practically, in every-day life every one acts upon the assumption that individual peculiarities are transmitted, with or without selection. Defects of body and mind, and liability to succumb to certain diseases, are also only too well known to be transmissible from one generation to another. Deaf-mutes have children who are deafmutes, though atavism hinders all the children from inheriting this defect; and the same remark applies to persons with supernumerary toes and fingers. Where one parent has been the victim of phthisis or of insanity, the children are in danger of succumbing to the same disease; where both parents have fallen victims, the chances are increased to a frightful degree. It is almost impossible to imagine how the strongest prepossessions against heredity can hold out in the face, not only of countless arguments from science, but of the practical experience of mankind in all ages..

Mr. Wallace devotes one chapter only to the geological evidence of evolution; but even in the very brief sketch he gives, there appears such overwhelming evidence of the influence of heredity and its effects in perfecting or aborting every organ of animals, and the slight, fine modifications in certain directions by which the changes from fossil to existing species have been effected, that one thinks he cannot remain unconvinced, and that he must believe these modifications to be hereditary. We almost doubt the evidence of our eyes when we read this passage, "There is now much reason to believe that the supposed inheritance of acquired modificationsthat is of the effects of use and disuse, or of the direct action of the environment-is not a fact." That is, we are to believe that all the modifications leading steadily upwards or downwards, the limbs perfected for speed of the horse and deer, the utter absence of limbs in certain lizards, the specialisation of the dentition of animals varying cusp by cusp and tooth by tooth, the improvement in brain capacity from Eocene times to our own, the persistence of rudimentary organs not only useless but dangerous to their present possessors; we are gravely asked to believe that all these modifications are the result of a series of accidents occurring generation after generation with results more and more marked, yet all uninherited and accidental! Can any one who has been impressed with the grand simplicity and

uniformity of the great Laws of Nature, believe that evolution is due to an infinite number of happy accidents? We know of a law which answers all those requirements of simplicity and uniformity of a great Law of Nature, which is in harmony with all the apparently complicated phenomena of life, which solves problems otherwise insoluble, the Law of the Action of the Environment upon Irritable Protoplasm. And we are asked to set it aside as nonexistent, and believe in innumerable accidental variations, as an efficient substitute !

Mr. Wallace refers, with high approval, to Professor Weismann's now celebrated lectures. If the theory which Professor Weismann considers he has proved in his laboratory is contradicted by the evidence of zoologists and paleontologists, as well as by the universal practical experience of mankind, then it is clear that laboratory work will not explain everything, and that the methods employed have been erroneous. But what shall we say when we are asked to accept a theory of which there is not one iota of tangible proof, which is, if anything, entirely contradicted by facts, and to accept this hypothesis as the only side of the medal? Professor Weismann's theory in brief is that the "substance which forms. the foundation of all the phenomena of heredity, in my opinion, can only be the substance of the germ-cells, and this substance transfers its hereditary tendencies from generation to generation, and is always uninfluenced in any corresponding manner by that which happens in the lifetime of the individual. If these views be correct, all our ideas upon the transformation of species require thorough modification, for the whole principle of evolution by means of exercise (use and disuse) as proposed by Lamarck, and accepted in some eases by Darwin, entirely collapses."*

When we read that views held not only by Lamarck, but by a host of illustrious men of science who have evidence at their command, which Lamarck and Darwin would have given worlds to possess, are to collapse before a certain theory, we expect this theory to have been founded on something that has at least been seen and observed. But it turns out that everything has to be "assumed." The assumption is that only a part of the germ-cell is used in the formation of the future animal; the remainder of the cell as " germ-plasm" is reserved to be handed on to future generations. I have endeavoured to reproduce this idea by a rough diagram.

"The germ cells † are not derived at all, so far as their essential substance is concerned, from the body of the individual, but they are derived directly from the parent germ-cell." The body (somatic) cells have, Prof. Weismann repeatedly declares, nothing whatever to do with the production of the germ-plasm.

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Yet he goes on to say that in all cases but that of the Diptera,* "generative cells arise from some of the later embryonic cells, and as these belong to a more advanced ontogenetic stage in the development of the idioplasm,† we can only conclude that continuity is maintained by assuming, as I do, that a small part of the germ-plasm remains unchanged during the division of the first segmentation nucleus, and remains mixed with the idioplasm of a certain series of cells, and that the formation of true germ-cells is brought · about at a certain point in the series by the appearance of cells in which the germ-plasm becomes predominant. But if we accept this hypothesis, it does not matter theoretically" [the italics are mine] "whether the germ-plasm becomes predominant in the third, tenth, hundredth or millionth generation of cells." In the same way, when we are dealing with imaginary fortunes, it does not matter whether we endow our hero with a thousand pounds a year or a million. We seem landed in the happy old days when one philosopher derived everything from fire, and another derived everything from water, and one hypothesis did just as well as another theoretically. The germ-plasm, which governs heredity, may exist or it may not; nobody has seen it, nor is likely to see it unless the laws of optics change. Something conveys hereditary tendencies in a mannor as extraordinary as it is mysterious. The hermaphrodite worm, which, if ontogeny does not deceive us, was the ancestor of the vertebrata, has impressed his nature upon all of us in the form of innumerable embryonic and rudimentary structures.‡

Prof. Weismann may be perfectly correct so far as he maintains that heredity is the work of his germplasm, and the manner in which he works out this part of his theory is delightful. It is when he claims that variability is also the characteristic of his imaginary substance, to the exclusion of any influence exerted by the somatic cells, that one refuses to accept theory in place of facts. He will look only at his own side of the medal, though he appears sincerely to wish to look at the other as well. Eyes do not atrophy through disuse; short sight is not inherited; a pointer doesn't point because his ancestors have been trained to point, but through a predisposition on the part of the germ.§ A predisposition to point on the part of a germ! He denies even the heredity of instinct, and says there is no transmission of acquired skill even in insects! Where facts are so overwhelmingly strong that it is impossible to meet them, he always says our knowledge on the subject is still very defective." Let us only know more, and the germ will be proved all-potent. In the meantime The complacently says: "The inheritance of acquired

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characters has never been proved either by means of direct observation or by experiment"! Such an assertion takes one's breath away, and makes one wonder how far a very eminent man can be blinded by a theory.

This fatal tendency to adapt all facts to a foregone conclusion or a pet theory, and to minimise or ignore those that militate against it, the inability or the unwillingness to look at both sides of the medal, is seen in every department of science. The greatest minds have been keenly alive to this danger, and nc more illustrious example can be found of devotion to truth at all costs than that of Newton.* His early theories on the law of gravitation were given up by him as untenable, because of difficulties in reconciling this law with the motions of the moon in her orbit. His study of the subject was only resumed after a lapse of eleven years. Yet Newton's original calculations and his theory were perfectly correct, only the original calculations were founded on an erroneous estimate of the length of a degree of latitude on the earth's surface, which had to be corrected before theory and facts could agree. Many of the theories. of this illustrious Englishman "were left in an imperfect state, for it is not in matters of science that it is given to the same individual to invent and to bring to perfection. Their complete development required that several subsidiary sciences should be farther advanced." Fortunately no zealous friend was found to treat the conclusions of Newton as final, and dub them Newtonism'! The words of Mr. Proctor, just quoted, may most fitly be employed in speaking of the theories of one not less illustrious than Newton; of one not less scrupulously anxious that his theories should be confirmed at all points by facts; yet of one who could not see his grand hypothesis of evolution attain to its full development, because this required that "several subsidiary sciences should be farther advanced." We do not hear of a School of Newton,' priding itself on firmly making a stand at the point to which the great philosopher, with the imperfect data at his command, had attained; why in the name of science, or rather of simple common sense, should we hear of anything so absurd as a "Darwinian school." How earnestly would the great master himself have deprecated such an absurdity. His own mind was constantly open to the reception of new ideas. What mattered it to him that some of these ideas threatened to conflict with the brilliant hypothesis, on which much of his fame rested, ie., the development of species through natural selection. All that he cared for-all that he had ever cared for in science, was to ascertain the truth; and again and again in his works he deplores the imperfect data he had to work from. Especially does he deplore the extreme imperfection of the geological record, and it is on

"Encyclopædia Britannica," articles 'Newton,' p. 441, and 'Astronomy,' p. 756.

this very point that the most gigantic strides have been made in our knowledge of late years.

I will quote a few passages showing the feelings of Darwin on this subject, and how far he was from making a fixed creed of his own conclusions.

"In many cases it is most difficult even to conjecture by what transitions organs have arrived at their present state."*

"In searching for the gradations through which an organ in any species has been perfected, we ought to look exclusively to its lineal progenitors; but this is scarcely ever possible." †

It is hardly necessary to say what brilliant work has elucidated these difficulties of late years. Embryologists have traced the stages through which every part of the future animal passes on its way to its own form of differentiation; as for instance the modifications of the bones in the leg and wing of the chick, in which, at an early period the indications of a former five-toed condition can be seen; the germs of teeth destined never to cut the gum, and the consolidation of the bones in ruminants and equidæ ; and the three sets of kidneys in vertebrates.

Paleontologists have had successes as brilliant; they can show the phylogeny of an immense number of our present mammals, whilst the embryologists have demonstrated their ontogeny: the " "lineal pro. genitors" have been found. Darwin says, "Two forms can seldom be connected by intermediate varieties, and thus proved to be the same species, until many specimens are collected from many places ; and with fossil species this can rarely be done. We shall perhaps best perceive the improbability of our being able to connect species by numerous fine intermediate fossil links, by asking ourselves whether, for instance, geologists at some future period will be able to prove that our different breeds of cattle, sheep, horses, and dogs are descended from a single stock or from several aboriginal stocks. . . . This could be effected only by his discovering in a fossil state numerous intermediate gradations; and such success is improbable in the highest degree." This success, which the great master thought "improbable in the highest degree" has been attained; and the "numerous, fine, intermediate gradations in the fossil state," have been traced.

Again, in arguing with writers who assert the immutability of species by asserting that geology yields no linking forms, he says,§ "If we take a genus having a score of species, recent and extinct, and destroy four-fifths of them, no one doubts that the remainder will stand much more distinct from each other.... What geological research has not revealed is the former existence of infinitely numerous gradations, as fine as existing varieties, connecting together nearly all existing and extinct species. But this ought not to be expected." So far is the great

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master from hoping, that before one generation had grown up since his death, these "infinitely numerous variations, as fine as existing varieties," "connecting existing with extinct species"; "these numerous, fine, intermediate fossil links" would be found in countless numbers, and that the ancestral forms not

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Fig. 7.-a, reproductive cell; b, nucleus, which after extrusion of the polar globules will form the future animal or plant; germ-plasm" left over to carry on the qualities of ancestors, and transferred from generation to generation. Whatever changes occur in an animal are due entirely to modifications of the "germ-plasm."

only of our "different breeds of cattle, sheep, horses and dogs," but those of the bear, the cat, the weasel, the rhinoceros, the camel and of countless other animals would be accurately known.*

And, with regard to his own special hypothesis of evolution through natural selection, he speaks again and again of our ignorance of the causes which have given rise to those variations upon which natural selection has to work. The battle which Darwin had to fight was to prove the evolution and consequent changeability of species, in opposition to opponents who believed in the special creation and unchangeability of species. Having had that great battle won for them, scientific men have had leisure to turn their attention to the cause of the variations controlling evolution. Later in his life, after having borne the burden and heat of the day, Darwin had more leisure to turn his own attention to this most important question. The following extracts will exemplify the earlier and later phases of his opinions on this subject:-" Variations appear to arise from the same unknown causes acting on the cerebral organization, which induce slight variations or individual differences in other parts of the body; and these variations, owing to our ignorance, are often said to arise spontaneously."† (The italics are mine.) After speaking of the number of facts collected with respect to the transmission of the most trifling, as well as of the most important characters in man, and also in domestic animals, he says: "With regard to the causes of variability, we are in all cases very ignorant." And again, he speaks of the "complex and little-known laws governing the production of varieties," being "the same, so far as we can judge, as the laws which have governed the production of distinct species." +

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appears that I formerly underrated the frequency and value of these later forms of variation" (viz. adaptive structures which have arisen by the direct action of external conditions). "But as my conclusions have lately been much misrepresented, and it has been stated that I attribute the modification of species exclusively to natural selection, I may be permitted to remark that. . . . I placed in a most conspicuous position the following words: 'I am convinced that natural selection has been the main, but not the exclusive means of modification.' This has been of no avail. Great is the power of steady misrepresentation, but the history of science shows that fortunately this power does not long endure." But his views were gradually changing as to the importance of the action of the environment in evolution; and in one of his later letters he says: "In my opinion the greatest error which I have committed has been not allowing sufficient weight to the direct action of the environment, independently of natural selection.” *

We have an equally fine instance of the willingness to accept new ideas, however much they might apparently be in opposition to his own views, in the attitude of Mr. Herbert Spencer towards this very theory of natural selection. As early as 1864, in his "Principles of Biology,"† with that prophetic instinct which characterises genius, he had laid down those principles of evolution now often spoken of as Neo-Lamarckian. For Lamarck, animated by the same prophetic genius, had foreseen the prepotent power of the action of environment, though his data were so imperfect, so apparently empirical, that his theory was laughed to scorn. Mr. Herbert Spencer had pointed out the influence of the environment on the very simplest unicellular organisms, had traced it up to more and more complex organisms, had shown its influence upon every part of the body and its struggle with atavism, or the principle of heredity so strongly possessed by all animal and vegetable cells. Of the many hundreds of brilliant discoveries in chemistry, pathology, biology, and palæontology, which from every side now confirm his theories, he could not then avail himself; yet his conclusions are confirmed in almost every instance by what these sciences have revealed to us. Yet in his "Factors of Organic Evolution," published twenty-two years later, he is ready to resign his victor's wreath to Darwin, he acknowledges him as a teacher, and bears witness to the priceless services rendered to the cause of the evolutionary theory by the publication of the "Origin of Species." He sees both sides of the medal, but he does not at that date appear to have grasped the fact that each side belongs to the same medal, and that natural selection is only one manifestation of that great Law of the Action of the Environment on all organic beings, of which he was

* "Life and Letters of Charles Darwin," vol. ii., p. 338. +"Principles of Biology," pp. 7, 12, 72, 74, 75, 80, 83, 226, 235, 294, 296, 311, 322, &c.

the brillant exponent. In its simplest manifestation it influences the protoplasm of unicellular organisms; in its more complicated manifestations it decrees the extermination of the South Sea Islanders, by the alien civilisation, the diseases, and the rum of the white man. It dwarfs the pines on the tundras of Siberia till they finally dwindle into trailing weeds four to five inches high; it increases the size, or the speed, or the marketable value, whatever it may be, of our domestic animals; it has changed the fierce wolf and the cowardly jackal into the only animal which has won, by its high mental and moral qualities, the title of the friend of man. * It has been proved that the action of the environment, and no mysterious "vital force" preserves the liquid condition of the blood in living veins, or causes its coagulation. No function is too high or too low for its all-pervading influence; just as the law of gravitation acts upon the minutest speck of matter, as inflexibly as it acts upon the solar system.

I trust that in this necessarily imperfect sketch I have at least shown how unjustifiable is the attempt to associate the great name of Darwin with the unprogressive school which arrogates to itself the right of claiming to be his special disciples. To demonstrate fully how baseless in ascertained fact is Professor Weismann's theory of "germ-plasm " would require a special article; but I have endeavoured to indicate a few of its weak points, and to show its constant need of assumptions as bases of reasoning.

NOTES ON NEW BOOKS.

RESEA

ESEARCHES ON MICRO-ORGANISMS, by Dr. A. B. Griffiths (London: Baillière, Tindal, & Cox). Dr. Griffiths is well known as one of the most painstaking and industrious of our younger school of scientists, and he has here produced a very useful manual of reference, which includes an account of all the recent experiments on the destruction of Microbes in various infectious diseases, and is illustrated by fifty-two woodcuts, Just at present Bacteriology is dominant, ten years ago hardly a few scores of people knew what the term meant. A general knowledge of the subject is now incumbent on all medical men, apothecaries, and journalists. Dr. Griffiths, however, does not claim his book to be a manual of Bacteriology, after the manner of Dr. Crookshank. It is rather an exposé of the researches which throw light on the pathology and therapeutics of certain infectious diseases. Nevertheless, it throws a very large cast-net over the whole field of the subject, including an outline of the natural history of Microbes in general; their microscopical examination, classification, cultivation, distribution in earth, air, and water; the various

For the ancestry of the dog, see "The Mammalia," by Oscar Schmidt. International Scientific Series.

methods of micro-biological research, the nature of various ferments; production of Ptomaines; special ferments; the various substances secreted by Microbes; the action of heat on microbes and their spores; an account of the researches of Koch, Klein,. Pasteur, Bert, Parsons, Duclaux, Forster, and others, to which we are pleased to see the author has added his own, which are not the least interesting. There are also lengthy and varied chapters on Germicides and antiparasitic therapeutics; the General Biology of the Microbes of Rabies, Yellow Fever, Pleuropneumonia, Foot-and-mouth Disease, Cattle Plague, Pyæmia, Septicœmia, Puerperal Fever, Syphilistuberculosis, Anthrax, Swine Fever, &c. The last chapter is an excellent summary of the recent experiments on the destruction of microbes in infectious diseases, in which, of course, those of Professor Koch occupy a prominent position. Dr. Griffiths has produced a useful as well as a thoroughly good book.

Astronomical Lessons, by J. E. Gore (London: Sutton, Drowley, & Co.). We cordially recommend this well got up little book, the work of a wellknown astronomer and astronomical writer, as one of the best introductions to the study of the "noble science" we have yet come across. It contains twenty-two short chapters dealing with a large and general range of astronomical knowledge, all of course brought up to the most recent date. The book is well illustrated.

Applied Geography, by J. Scott Keltie (London: George Philip & Son). This is altogether a novel and acceptable departure from the too traditional method of teaching geography. Much of its contents have appeared as articles in leading magazines, lectures given before the Society of Arts, the College of Preceptors, the Bankers' Institute, etc., and the book is illustrated by excellent illustrative maps.. It contains five chapters headed as follows:"Preliminary Considerations," 'Geography applied to Commerce," "The Geography of Africa in its Bearings on the Development of the Continent,” (two chapters on this all-important subject), "The British Empire," and "Some Common Commodities."

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London of the Past, by J. Ashton Ainscough. (London: Elliot Stock). This is a small, delightfully written and accurate history of the most wonderful' and interesting city in the world. It is a straightforward narrative, neither encumbered with comment nor laden with petty details.

Elementary Treatise on Hydrodynamics and Sound, by A. B. Bassett, F.R.S. (Cambridge: Deighton,. Bell & Co.). The author's fame as a mathematician is well known, and his previous works on these special subjects have deservedly acquired for him the rank of an authority. It is a most useful work on mathematical physics, and includes much which will prove valuable to mathematical electricians par

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