For those not fluent in German, my translation follows. Highlights are my additions. [Square brackets contain my own comments.] They are not part of May's review:
Darwin and Patrick Matthew. By Prof. Dr. Walther May, Karlsruhe i. B. (With a Portrait.) [omitted]
"It probably belongs to the essence of each discovery," says Rádl in his history of biological theories, "that it struggles for recognition; it forces its wearer to inform you, to fight for them and not infrequently also to suffer. Thousands of ideas struggle for recognition; but most founder in the souls of the absent-minded listening world. The historian must not close his eyes to this fact; he must seek the truth not only to the throne of public recognition, but wherever people think. Through a game of coincidences, an idea is off and on promoted or suppressed; the historian should not be bribed by this, because his goal is to recognize ideas and not to describe the glory of the world. Even if a discovery sank without a trace in the hassles of opinions, it does not therefore cease to form the subject of historiography."
These words encourage me to renew the memory of a man, whose idea did not go down without a trace, but was disregarded for almost thirty years, before it was awakened by another, larger, to actual life.
On April 10, 1860 Darwin wrote to Lyell:
"In last Saturday Gardeners’ Chronicle, a Mr Patrick Matthews publishes long extract from his work on “Naval Timber & Arboriculture” published in 1831, in which he briefly but completely anticipates the theory of Nat. Selection.—12 I have ordered the Book, as some few passages are rather obscure but it, is certainly, I think, a complete but not developed anticipation! Erasmus always said that surely this would be shown to be the case someday. Anyhow one may be excused in not having discovered the fact in a work on “Naval Timber”."
And three days later he wrote to Hooker:
"Questions of priority so often lead to odious quarrels, that I shd. esteem it a great favour if you would read enclosed. If you think it proper that I shd. send it (& of this there can hardly be question) & if you think it full & ample enough, please alter date to day on which you post it & let that be soon.— The case in G. Chronicle seems a little stronger than in Mr. Matthews book, for the passages are therein scattered in 3 places. But it would be mere hair-splitting to notice that.— If you object to my letter please return it; but I do not expect that you will, but I thought that you would not object to run your eye over it."
On April 21, 1860 "Gardeners Chronicle" brought the following letter Darwin:
"I have been much interested by Mr. Patrick Matthew’s communication in the Number of your Paper, dated April 7th. I freely acknowledge that Mr. Matthew has anticipated by many years the explanation which I have offered of the origin of species, under the name of natural selection. I think that no one will feel surprised that neither I, nor apparently any other naturalist, had heard of Mr. Matthew’s views, considering how briefly they are given, and that they appeared in the appendix to a work on Naval Timber and Arboriculture. I can do no more than offer my apologies to Mr. Matthew for my entire ignorance of his publication. If another edition of my work is called for, I will insert a notice to the foregoing effect."
[Interestingly, May translated the word "naturalist" used by Darwin above as "Naturforscher" into German. Naturforscher, however, means natural scientist or researcher or explorer. Thus May explicated a connotation of the term naturalist in Darwin's use above, that is easily lost in English.]
According to Francis Darwin, Matthew was not satisfied by this explanation and complained in November 1860, that an article in the "Saturday Analyst and Leader" was hardly fair in calling Darwin the father of the theory of natural selection, because he himself had published all that Darwin tried to prove more than 29 years ago.
Darwin also recognized Matthew's claims unreservedly in a letter to Quatrefages of 25 April 1861. "I have," he writes there, "lately read M. Naudin’s paper; but it does not seem to me to anticipate me, as he does not shew how Selection could be applied under nature; but an obscure writer on Forest Trees, in 1830, in Scotland, most expressly & clearly anticipated my views—though he put the case so briefly, that no single person ever noticed the scattered passages in his book."
Later Darwin found that even Matthew had a predecessor still. "Talking about the Origin," he wrote to Hooker in October 1865, "a Yankee has called my attention to a paper attached to Dr Well’s famous Essay on Dew, which was read in 1813 to Royal Soc. but not printed, in which he applies most distinctly the principle of N. Selection to the races of man.—So poor old Patrick Matthew, is not the first, & he cannot or ought not any longer put on his Title pages “Discoverer of the principle of Natural Selection”!"
In the historical sketch, that Darwin prefixed to the later editions of his "Origin of Species," he appreciates the Matthew's merits as follows:
"In 1831 Mr. Patrick Matthew published his work on 'Naval Timber and Arboriculture,' in which he gives precisely the same view on the origin of species as that (presently to be alluded to) propounded by Mr. Wallace and myself in the 'Linnean Journal,' and as that enlarged in the present volume. Unfortunately the view was given by Mr. Matthew very briefly in scattered passages in an appendix to a work on a different subject, so that it remained unnoticed until Mr. Matthew himself drew attention to it in the 'Gardener's Chronicle,' on April 7th, 1860. The differences of Mr. Matthew's view from mine are not much importance: he seems to consider that the world was nearly depopulated at successive periods, and then re-stocked; and he gives as an alternative, that new forms may be generated "without the presence of any mould or germ of former aggregates." I am not sure that I understand some passages; but it seems that he attributes much influence to the direct action of the conditions of life. He clearly saw, however, the full force of the principle of natural selection."
In the same historical sketch Darwin says about Owen's priority claims:
"As far as the mere enunciation of the principle of natural selection is concerned, it is quite immaterial whether or not professor Owen preceded me, for both of us, as shown in this historical sketch, were long ago preceded by Dr Wells and Mr. Matthews."
Besides these judgments by Darwin of Matthew, I only know of two further in the Darwinian literature. Regarding Darwin's remarks on Matthew in the historical sketch, Samuel Butler wrote, in his book "Evolution, Old & New," in 1879:
"Nothing could well be more misleading. If Mr. Matthew's view of the origin of species is "precisely the same as that" propounded by Mr. Darwin, it is hard to see how Mr. Darwin can call those of Lamarck and Dr. Erasmus Darwin "erroneous"; for Mr. Matthew's is nothing but an excellent and well-digested summary of the conclusions arrived at by these two writers and by Buffon. If, again, Mr. Darwin is correct in saying that Mr. Matthew "clearly saw the full force of the principle of natural selection," he condemns the view he has himself taken of it in his 'Origin of Species,' for Mr. Darwin has assigned a far more important and very different effect to the fact that the fittest commonly survive in the struggle for existence, than Mr. Matthew has done. Mr. Matthew sees a cause underlying all variations; he takes the most teleological or purposive view of organism that has been taken by any writer (not a theologian) except myself, while Mr. Darwin's view, if not the least teleological, is certainly nearly so, and his confession of inability to detect any general cause underlying variations, leaves, as will appear presently, less than common room for ambiguity."
Contrary to Butler and agreeing with Darwin, Grant Allen called Patrick Matthew the unconscious discoverer of the principle of natural selection in his Darwin Biography (1888), who applied the selection idea, in his book on naval timber, to the whole of nature, sometimes with the same words as Darwin."
I was led to concern myself with Matthew and his work through an external circumstance. Prof. Dr. P. Unna in Hamburg sent me, on the occasion of the Darwin anniversary in 1909, a letter of the Hamburg pastor, Dr. H. F. Beneke, whose uncle Alexander Matthew (died on 18 January 1911 at the age of 90) was the son of Patrick Matthews. This letter alluded to the priority of Matthew. I then asked the Pastor Beneke for the book and for some biographical notes about his great uncle and received both in amiable manner. Here are the biographical data:
"Patrick Matthew, born October 20, 1790, died June 8, 1874, married his cousin Christian Nicol (born December 21, 1791, died October 28, 1857). Both their mothers were sisters, born Duncan. From the Duncans he inherited the Gourdie Hill property, actually with the condition to take the name Duncan, what he did not. (The land is now no longer in the family). We also know the names of his parents John Matthew and Agnes Duncan and his grandparents Patrick Matthew in the Rome property on Tay and Helen Millar Broambrae from Fife, but do not have dates for them.
He must have married about 1819, as the eldest son Robert was born in 1820 and my uncle in 1821. He first managed both Rome and Gourdie Hill, later the latter alone. His picture, as an old man, shows beautiful, noble and pleasant features.
According to family tradition, the Matthews descended from a sister of Robert Bruce, and they are proud to have very square chins, as R. Bruce used to have; but that will of course be treated more jokingly."
The work on which Patrick Matthew based his priority claims against Darwin, bears the title: "On naval timber and arboriculture:; with critical notes on authors who have recently treated the subject of planting.' It is published by Adam Black, Edinburg; Longman, Rees, Orme, Brown and Green, London, and published in 1831. The content includes XVI and 391 big octavo pages and is organized as follows:
[list of contents omitted]
Matthews book is imbued with the patriotic spirit of the Englishman, who desires world domination of his nation. The means to this is for him the seafaring. In the introduction, he noted that the seafaring was of the greatest importance for the improvement of the species, naval superiority almost synonymous with universal dominion, the mainland only the footstool of the mistress of the seas. The periodic recurrence of war seems to him indispensable for the heroic, chivalrous character and the love of freedom. Conflict and fighting should rub the rust from the customs and institutions of his people, the ennobling appeal of danger should arouse the noble passions and the youth be led to emulate the Romans in patriotic thirst for fame, the Spartans in devotion, their own ancestor in bold bravery. Without seeking war, but in preparation to face an enemy, in perhaps not so distant a time, England should maintain its military virtues without malignant sentimentality, especially that which must make up the field of his fame, his navy and their building materials, naval timber.
Here, it is already indicated that the struggle among nations serves their refinement, but without pronouncing the principle of selection.
[May skipped the second part, probably because it is about ship-building and contains no passage relevant to natural selection.]
In the third part of the book artificial selection is an issue and natural selection is also hinted at. Since the luxuriance and size of timber is highly dependent on the peculiar variety of species, on the treatment of the seed prior to sowing, and on the treatment of the young plant, and since this fundamental issue is neither much appreciated nor widely understood, Matthew wants to discuss it from scratch. He speaks of the consequences of our lamentable ignorance of the most undeniable facts of natural history: that both the plants and the animals are subjected to an almost unlimited variability in general, due to the climate, the soil, the food and new blending of already formed varieties. In such species, with which man is very familiar, he had become acquainted with these facts, that is, in man himself, the dog, horse, cattle, sheep, poultry, apple, pear, plum, gooseberry, potato and pea, that feature endless varieties, by differing considerably in size, color, taste, firmness of texture, growing season and any recognizable property. In all these species, man seeks to avoid deterioration by careful selection of the biggest and most valuable for further growth, but with timber trees, the inverse procedure was followed. The tall-growing varieties were often cut off prematurely, because of their late seed production, small-growing and weak varieties, in which seed production takes place early and abundantly, on the other hand, had constantly been selected to reproduce because of the ease and convenience with which seeds can be obtained. "May we, then, wonder," asks Matthew, "that our plantations are occupied by a sickly short-lived puny race, incapable of supporting existence in situations where t heir own kind had formerly flourished—particularly evinced in the genus Pinus, more particularly in the species Scots fir; so much inferior to those of Nature's own rearing, where only the stronger, more hardy, soil-suited varieties can struggle forward to maturity and reproduction?"
This last sentence clearly stated that a selection takes place in nature, leading to the perfection of the race, but the emergence of new species by natural selection is not alleged here.
Matthew demands that the farmer gives as much attention to the breeding of his forest trees as to that of his horses, cows and sheep, that he only sows seeds collected from the largest, healthiest and most lavishly growing trees and desists from sowing seeds of precocious or even of the very old and overripe trees, because, by analogy with animals, a weak and early decaying progeny is to be expected from them.
In the fourth part of his book Matthew says that the benefit of endless seed varieties in the families of plants, even those under nature, probably lies in the fact that one individual (the strongest and best circumstances suited) gains the superiority over others, surpassing and suppressing them, creating space for its full extension and thus at the same time accomplishing a consistent selection of the strongest, best adapted to reproduce. The intervention of man has increased the diversity of varieties, regardless of the new conditions to which he introduced them, by preventing the natural process of selection among the plants, particularly in the more domesticated species, and even in man himself the greater equality and larger strength of the wild tribes can be ascribed to a similar law of selection, in which the weaker individual perishes under the poor treatment on the part of the stronger or from general depression.
Again, natural selection is considered only as a means of racial improvement and not as a cause of the emergence of new species.
Matthew clearly expressed the principle of natural selection as an adapting and perfecting principle in Note B of the Appendix ,"There is," he says here, "a law universal in nature, tending to render every reproductive being the best possibly suited to its condition that its kind, or that organized matter, is susceptible of, which appears intended to model the the physical and mental or instinctive powers, to their highest perfection, and to continue them so. This law sustains the lion in his strength, the hare in his swiftness, and the fox in his wiles. As Nature, in all her modifications of life, has a power of increase far beyond what is needed to supply the place of what falls by Time's decay, those individuals who possess not the requisite strength, swiftness, hardihood, or cunning, fall prematurely without reproducing—either a prey to their natural devourers, or sinking under disease, generally induced by want of nourishment, their place being occupied by the more perfect of their own kind, who are pressing on the means of subsistence."
Matthew continues this discourse with an argument against hereditary nobility and the law of entail, which appears to him as a mockery of the law of selection, that nature will not let unavenged. He referred to the role of hereditary nobility played in France, the Iberian and Italian peninsula and the Italian islands, and calls on the apologists of the hereditary nobility, primogeniture and the law of entail to say what these countries could have been without the corrupting influence of these unnatural morals. He sees intermittent mixing of the nobility with the people as the only way to protect those against degeneration. In some countries, this mixing would not be necessary as often as as in others, and Britain could be considered as the ground on which the nobility can remain unspoiled the longest. Approaching the equator, however, the renewal would often be necessary, except in high altitudes, in many places every third generation. The repeal of the law of inheritance and primogeniture would increase not only the happiness of the owner in the present state of civilization, increase mortality and give the social order greater strength, but also give the hard work and progress a general incentive whereby the living conditions of the working class would be improved.
Even Darwin has called primogeniture a means that was contrary to the action of natural selection. "Our aristocracy," he once wrote to Wallace, "is handsomer (more hideous according to a Chinese or Negro) than middle classes from pick of women; but oh what a scheme is primogeniture for destroying N. Selection." And in the fifth chapter of the "Descent of Man" he discussed the deleterious effects of this system in greater detail, but without neglecting the balancing factors."
In note C of the Appendix, Matthew examines the causes which have brought about the superiority of a part of the Caucasian race. He finds them mainly in repeated change of place under favorable circumstances. "There are few countries," he says, "where the old breed has not again and again sunk before the vigour of new immigration; we even see the worn out breed, chased from their homes to new location, return, after a time, superior to their former vanquishers, or gradually work their way back in peace, by superior subsisting power: this is visible in France, where the aboriginal sallow Kelt, distinguished by high satyr-like feature, deep-placed sparkling brown or grey eye, narrowed lower part of the face, short erect vertebral column, great mental acuteness, and restless vivacity, has emerged from the holes of the earth, the recesses of the forests and wastes, into which it had been swept before the more powerful blue-eyed Caucasian; and being a smaller, more easily subsisting animal, has, by starving and eating out, been gradually undermining the breed of its former conquerors."
But even more than the change of location the related circumstances have their share in the perfection of the species. In the unrest that accompanied the emigration, the varieties strongest in mind and body take over the leader role, impressing their character onto the people at large and constituting the reproductive part, while the weaker varieties generally perish at the occasional hardships. When a cohort emigrates from a community, it will generally consist of the bolder and brisked spirits, who will use the right of the conquerors to connect with the best of the natives that they overwhelm; their choice among these will be determined by personal characteristics and not by the accidental circumstances of wealth or high birth—a consideration which leads to the degradation of the race and one of the reasons, why the nobility of Europe is so inferior in comparison with the Asian.
Again, selection is only recognized as a means of racial improvement.
In note D Matthew repeats the thought, already indicated in the introduction, that national power and size is impossible without the operation of the egotistical drives. Our milder manners, our benevolence our tranquility, kindness and sense of refinement our sweet dreams of peace and joy, he calls a negative weight in the scales of national strength. The stronger excitation of hatred, ambition, pride, patriotism and more selfish passions, he deems necessary for the full and strong development of national energy. That Britain had impressed its ability and morality to a considerable extent onto the world, is due to the fact that it first ravaged these countries with fire and sword.
These words remind us of the consequences that have drawn some modern racial theorists and many anti-darwinian ethicists from Darwinism.
[May skipped the end-notes E and F of the appendix. Note E was on the improper calculation of register tonnage of trading vessels leading to ill constructions of the vessels, in order to safe charges for lights, harbours and other dues. Note F was on the geological history of the North Sea, which Matthew called the German Ocean. Next May refers to a "long epilogue." This is actually a colophon following after the end of Note F and a horizontal line indicating this. Whereas footnotes in the main text refer to the end-notes A-F of the appendix, the main text contains no reference to this colophon suggesting that it was an afterthought.]
Matthew concludes his work with a long epilogue, in which he set out his understanding of the evolution of organic life on Earth. Only here, he regarded natural selection not only as a means of racial improvement and adaptation, but also as a cause of the origin of new species and the organic development at all. He speaks, first, of a power of change under a change of circumstances, which belongs to the living substance, or rather the hodgepodge of low life, which seems to form the higher, and that one must admit, if one does not want to accept a repeated wonderful creation. The changes that have happened as a result of human intervention with the domestic animals and crops before him, and the likelihood that the living conditions were very different in the various geological periods, but consistent within each, seem to prove to him the accuracy of the assumption that, at the beginning of each new age [meaning geological eras between catastrophes], no creation took place, but some organisms surviving from the former age have, again, adapted their existence over time to the change of circumstances and to every possible kind of living conditions. "Is the inference, then, unphilosophic," he asks, in consideration of the large chemical changes of the water and the atmosphere, "that living things, which are proved to have a circumstance-suiting power—a very slight change of circumstances by inducing a corresponding change of character—may have gradually accommodated themselves to the variations of the elements containing them, and, without new creation, have presented the diverging changeable phenomena of past and present organized existence."
Matthew evidently connects in his somewhat vague hypothesis the doctrine of catastrophism with the theory of evolution. He believes that the destructive liquid streams, which separated the ages and destroyed almost all living things, reducing being so much, that an unoccupied field got available for new diverging branches of life adapting itself to the new conditions and then, after completion of this adjustment, remained constant for the duration of their existence, except for the few residues that reached alive into the next following period.
Besides this theory of evolution and the doctrine of creation there is, according to Matthew, only one alternative explanation of organic changes, namely the assumption of an "indestructible or molecular life, gradually uniting and developing itself into new circumstance-suited living aggregates, without the presence of any mould or germ of former aggregates," which probably means the re-emergence of life by spontaneous generation, which Matthew distinguishes from new creation only by the fact that it "forms a portion of a continued scheme or system."
Thus, Matthew has taken his position concerning the three possible hypotheses of biogenesis, on creation, on spontaneous generation and on evolution, and he opted for the theory of evolution; but it can hardly be called an advance over the earlier development theorists such as Buffon, Erasmus Darwin and Lamarck, when he connects it to the doctrine of catastrophism.
Far more important than the views of Matthews on organic change in general are his ideas about the causes of these changes. Here he raises the following question: "Do they arise from admixture of species nearly allied producing intermediate species? Are they the diverging ramifications of the living principle under modification of circumstance? Or have they resulted from the combined agency of both? Is there only one living principle? Does organized existence, and perhaps all material existence, consist of one Proteus principle of life capable of gradual circumstance-suited modifications and aggregations?"
Matthew cannot accept that much of the changes in the organisms is owed to the mixing of closely related species, since all change is very limited by this, and limited in the circle of what is called species. He sees the main cause of change in the self-regulating adaptability of organisms, which he ascribes, at least partially, to the immense fertility of nature.
"Nature, who, as before stated, has, in all the varieties of her offspring," he says, "a prolific power much beyond (in many cases a thousandfold) what is necessary to fill up the vacancies caused by senile decay. As the field of existence is limited and pre-occupied, it is only the hardier, more robust, better suited to circumstance individuals, who are able to struggle forward to maturity, these inhabiting only the situations to which they have superior adaptation and greater power of occupancy than any other kind; the weaker, less circumstance-suited, being prematurely destroyed. This principle is in constant action, it regulates the colour, the figure, the capacities, and instincts; those individuals of each species, whose colour and covering are best suited to concealment or protection
from enemies, or defence from vicissitude and inclemencies of climate, whose figure is best accommodated to health, strength, defence, and support; whose capacities and instincts can best regulate the physical energies to self-advantage according to circumstances—in such immense waste of primary and youthful life, those only come forward to maturity from the strict ordeal by which
Nature tests their adaptation to her standard of perfection and fitness to continue their kind by reproduction.
From the unremitting operation of this law acting in concert with the tendency which the progeny have to take the more particular qualities of the parents, together with the connected sexual system in vegetables, and instinctive limitation to its own kind in animals, a considerable uniformity of figure, colour, and character, is induced, constituting species; the breed gradually acquiring the very best possible adaptation of these to its condition which it is susceptible of, and when alteration of circumstance occurs, thus changing in character to suit these as far as its nature is susceptible of change."
In these sentences, the principle of natural selection is expressed with full clarity and widely applied, and Darwin is certainly right when he says of Matthew "He clearly saw the full implications of the principle of natural selection." It is impossible to see how Butler can discard this interpretation of Matthew's train of thought, and claim that the Scottish writer has only represented the doctrines of Buffon and Erasmus Darwin. The principle of natural selection is there, although Matthew also added that this adaptive law does not exclude the influence of the will or feeling on the design of the body. Matthew just recognizes other factors of species transformation in addition to natural selection, exactly like Darwin did, on whose scope further research had to decide. "to investigate," he says, "how much variation is modified by the mind or nervous sensation of the parents, or of the living thing itself during its progress to maturity; how far it depends upon external circumstance, and how far on the will, irritability and muscular exertion, is open to examination and experiment. In the first place, we ought to investigate its dependency upon the preceding links of the particular chain of life, variety being often merely types or approximations of former parentage; thence the variation of the family, as well as of the individual, must be embraced by our experiments."
That is, Matthew already advocated the most modern direction of the development theory, the experimental.
In the further course of his argument, he stressed that the continuation of the family type is both physical and mental, and is evidenced by many of the dispositions or instincts of the different human races. He regarded these native or inherited ideas or habits, that prevail especially in insects, as an "abiding memory" and believed to solve a lot of the mystery of instinct and the foreknowledge that these animals have of what is necessary, in order to complete their round of life, by reducing the instincts to knowledge, or impressions, and habits, acquired by a long experience. So he explains, here, the instincts according to Lamarck's principle; that he also subjects them to natural selection, however, is clear from his earlier statements.
In discussing the instincts of insects, Matthew also touches on the problem of individuality. He finds it difficult to determine the specific points, in some insects, when each individuality begins with the different stages of egg, larva, pupa, or whether much consciousness of individuality exists.
The epilogue concludes with a reflection on the imbalance of nature introduced by humans. They have in the present age attained a mastery of the material world and a successful power of multiplication, which makes it likely that the whole surface of the earth will soon be overrun by this engrossing anomaly, to the annihilation of every wonderful and beautiful variety of animated existence, that does not administer the human needs.
It is admirable how many problems are touched in Matthew's book. However, only the attempt of a comprehensive application of the principle of selection on the whole organic nature is fundamentally new. All the other ideas of Matthew had already been expressed by earlier thinkers. Even the principle of natural selection as such had already been pronounced by Wells and Prichard, but they applied it to the races of man only. In comparison with this very limited application, Matthew's hypothesis seems to be a new thought. We can therefore call the Scottish landowner the first, who recognized natural selection as a general principle of nature, without scruple. But he does not seem to have considered this principle to be as important for biological science, as Darwin later adjudged it, otherwise he would not have published his ideas in the appendix to a work on naval timber. But even if he had published this idea, in the existing form, in a separate document, it would have had as little influence on the science, as had the short treatises that Wallace and Darwin published in 1858 on the theory of natural selection in the Journal of the Linnaean Society. Because, as Butler rightly remarks, the same reproach must be made against Matthew's abstract of the theory of evolution as to Erasmus Darwin's view of this theory, that it was in fact too short. "It may be true," says Butler, "that brevity is the the soul of the wit, but the leaders of science will generally succeed in burking new-born wit, unless the brevity of its soul is found compatible with a body of some bulk."
Darwin first gave the body to the soul of the theory of natural selection. The ingenious way in which he related the facts of almost all biological disciplines in terms of the selection idea into an organic whole, is his very own merit, that defies all other priority claims.
Allen, Qraot, Charles Darwin. London, Longmans, Green, and Co. 1888.
Butter, Samuel, Evolution, old and new. London, Hardwicke and Bogue, 1879.
Darwin, Charles, Die Entstehung der Arten. Deutsch von Victor Carus. 8. Auflage. Stuttgart, E. Schweizerbart, 1899.
Darwin, Francis, Leben und Briefe von Charles Darwin. Deutsch von Victor Carus. 2. Auflage. Stuttgart, E. Schweizerbart, 1899.
Darwin, Francis and A. C. Seward, More letters of Charles Darwin. London, John Murray, 1903.
Matthew, Patrick, On naval timber and arboriculture; with critical notes on authors who have recently treated the subject of planting. Edinburgh, Adam Black; London, Longman, Rees, Orme, Brown and Green, 1831.
Rádl, Em., Geschichte der biologischen Theorien. II. Teil. Leipzig, Wilhelm Engelmann, 1909.