Chapter VII: Part II: I.--The Discovery of Natural Selection (1)

"There are not many joys in human life equal to the joy of the
sudden birth of a generalisation, illuminating the mind after a
long period of patient research. What has seemed for years so
chaotic, so contradictory, and so problematic takes at once its
proper position within an harmonious whole. Out of the wild
confusion of facts and from behind the fog of
guesses--contradicted almost as soon as they are born--a stately
picture makes its appearance, like an Alpine chain suddenly
emerging in all its grandeur from the mists which concealed it the
moment before, glittering under the rays of the sun in all its
simplicity and variety, in all its mightiness and beauty. And when
the generalisation is put to a test, by applying it to hundreds of
separate facts which seemed to be hopelessly contradictory the
moment before, each of them assumes its due position, increasing
the impressiveness of the picture, accentuating some
characteristic outline, or adding an unsuspected detail full of
meaning. The generalisation gains in strength and extent; its
foundations grow in width and solidity; while in the distance,
through the far-off mist on the horizon, the eye detects the
outlines of new and still wider generalisations. He who has once
in his life experienced this joy of scientific creation will never
forget it; he will be longing to renew it; and he cannot but feel
with pain that this sort of happiness is the lot of so few of us,
while so many could also live through it--on a small or on a grand
scale--if scientific methods and leisure were not limited to a
handful of men."--PRINCE KROPOTKIN, "Memoirs of a Revolutionist."

The social and scientific atmosphere in which Wallace found himself on his return from his eight years' exile in the Malay Archipelago was considerably more genial than that which he had enjoyed during his previous stay in London following his exploration of the Amazon. His position as one of the leading scientists of the day was already recognised, dating from the memorable 1st of July, 1858, when the two Papers, his own and Darwin's, on the theory of Natural Selection had been read before the Linnean Society.

During the four years which had elapsed since that date the storm of criticism had waxed and waned; subsiding for a time only to burst out afresh from some new quarter where the theory bade fair to jeopardise some ancient belief in which scientist or theologian had rested with comparative satisfaction until so rudely disturbed.

During this period Wallace had been quietly pursuing his researches in the Malay Archipelago, though not without a keen interest in all that was taking place at home in so far as this reached him by means of correspondence and newspaper reports--his only means of keeping in touch with the world beyond the boundaries of the semi-civilised countries in which he was then living.

In order to follow the story of how the conception of the theory of Natural Selection grew and eventually took definite form in Wallace's mind, independently of the same development in the mind of Darwin, we must go back to a much earlier period in his life, and as nearly as possible link up, the scattered remarks which here and there act as signposts pointing towards the supreme solution which has made his name famous for all time.

In Part I., Section I., many passages occur which clearly reveal his awakening to the study of nature. A chance remark overheard in conversation in the quiet street of Hertford touched the hidden spring of interest in a subject which was to become the one great purpose of his life. Then his enthusiastic yielding to the simple and natural attraction which flowers and trees have always exerted upon the sympathetic observer led step by step to the study of groups and families, until, on his second sojourn at Neath, and about a year before his journey to South America with H.W. Bates, we find him deliberately pondering over the problem which many years later he described by saying that he "had in fact been bitten by the passion for species and their description."

In a letter to Bates dated November 9th, 1847, he concludes by asking, "Have you read 'Vestiges of the Natural History of Creation,' or is it out of your line?" and in the next (dated December 28th), in reply to one from his friend, he continues, "I have a rather more favourable opinion of the 'Vestiges' than you appear to have, I do not consider it a hasty generalisation, but rather an ingenious hypothesis strongly supported by some striking facts and analogies, but which remains to be proved by more facts and the additional light which more research may throw upon the problem.... It furnishes a subject for every observer of nature to attend to; every fact," he observes, "will make either for or against it, and it thus serves both as an incitement to the collection of facts, and an object to which they can be applied when collected. Many eminent writers support the theory of the progressive development of animals and plants. There is a very philosophical work bearing directly on the question--Lawrence's 'Lectures on Man'.... The great object of these 'Lectures' is to illustrate the different races of mankind, and the manner in which they probably originated, and he arrives at the conclusion (as also does Prichard in his work on the 'Physical History of Man') that the varieties of the human race have not been produced by any external causes, but are due to the development of certain distinctive peculiarities in some individuals which have thereafter become propagated through an entire race. Now, I should say that a permanent peculiarity not produced by external causes is a characteristic of 'species' and not of mere 'variety,' and thus, if the theory of the 'Vestiges' is accepted, the Negro, the Red Indian, and the European are distinct species of the genus Homo.

"An animal which differs from another by some decided and permanent character, however slight, which difference is undiminished by propagation and unchanged by climate and external circumstances, is universally held to be a distinct _species_; while one which is not regularly transmitted so as to form a distinct race, but is occasionally reproduced from the parent stock (like albinoes), is generally, if the difference is not very considerable, classed as a _variety_. But I would class both these as distinct _species_, and I would only consider those to be _varieties_ whose differences are produced by external causes, and which, therefore, are not propagated as distinct races."

Again, writing about the same period, he adds: "I begin to feel rather dissatisfied with a mere local collection; little is to be learnt by it. I should like to take some one family to study thoroughly, principally with a view to the theory of the origin of species. By that means I am strongly of opinion that some definite results might be arrived at." And he further alludes to "my favourite subject--the variations, arrangements, distribution, etc., of species."[17]

It is evident that in Bates Wallace found his first real friend and companion in matters scientific; for in another letter he says: "I quite envy you, who have friends near you attracted to the same pursuits. I know not a single person in this little town who studies any one branch of natural history, so that I am quite alone in this respect." In fact, except for a little friendly help now and then, as in the case of Mr. Hayward lending him a copy of Loudon's Encyclopedia of Plants, he had always pondered over his nature studies without any assistance up to the time of his meeting Bates at Leicester.

From the date of the above letter (1847) on to the early part of 1855--nearly eight years later--no reference is found either in his Life or correspondence to the one absorbing idea towards which all his reflective powers were being directed. Then, during a quiet time at Sarawak, the accumulation of thought and observation found expression in an essay entitled "The Law which has regulated the Introduction of Species," which appeared in the _Annals and Magazine of Natural History_ in the following September (1855).

From November, 1854, the year of his arrival in the East, until January or February, 1856, Sarawak was the centre from which Wallace made his explorations inland, including some adventurous excursions on the Sadong River. During the wet season--or spring--of 1855, while living in a small house at the foot of the Santubong Mountains (with one Malay boy who acted as cook and general companion), he tells us how he occupied his time in looking over his books and pondering "over the problem which was rarely absent from [his] thoughts." In addition to the knowledge he had acquired from reading such books as those by Swainson and Humboldt, also Lucien Bonaparte's "Conspectus," and several catalogues of insects and reptiles in the British Museum "giving a mass of facts" as to the distribution of animals over the whole world, and having by his own efforts accumulated a vast store of information and facts direct from nature while in South America and since coming out East, he arrived at the conclusion that this "mass of facts" had never been properly utilised as an indication of the way in which species had come into existence. Having no fellow-traveller to whom he could confide these conclusions, he was almost driven to put his thoughts and ideas on paper--weighing each argument with studious care and open-eyed consideration as to its bearing on the whole theory. As the "result seemed to be of some importance," it was sent, as already mentioned, to the _Annals and Magazine of Natural History_ as one of the leading scientific journals in England.

In the light of future events it is not surprising that Huxley (many years later), in referring to this "powerful essay," adds: "On reading it afresh I have been astonished to recollect how small was the impression it made."

As this earliest contribution by Wallace to the doctrine of Evolution[18] is of peculiar historical value, and has not been so fully recognised as it undoubtedly deserves, and is now almost inaccessible, it will be useful to indicate in his own words the clear line of argument put forth by him two years before his second essay with which many readers are more familiar. He begins:

Every naturalist who has directed his attention to the subject of
the geographical distribution of animals and plants must have been
interested in the singular facts which it presents. Many of these
facts are quite different from what would have been anticipated,
and have hitherto been considered as highly curious but quite
inexplicable. None of the explanations attempted from the time of
Linnæus are now considered at all satisfactory; none of them have
given a cause sufficient to account for the facts known at the
time, or comprehensive enough to include all the new facts which
have since been and are daily being added. Of late years, however,
a great light has been thrown upon the subject by geological
investigations, which have shown that the present state of the
earth, and the organisms now inhabiting it, are but the last stage
of a long and uninterrupted series of changes which it has
undergone, and consequently, that to endeavour to explain and
account for its present condition without any reference to those
changes (as has frequently been done) must lead to very imperfect
and erroneous conclusions.... The following propositions in
Organic Geography and Geology give the main facts on which the
hypothesis [_see_ p. 96] is founded.

GEOGRAPHY

(1) Large groups, such as classes and orders, are generally spread
over the whole earth, while smaller ones, such as families and
genera, are frequently confined to one portion, often to a very
limited district.

(2) In widely distributed families the genera are often limited in
range; in widely distributed genera, well-marked groups of species
are peculiar to each geographical district.

(3) When a group is confined to one district and is rich in
species, it is almost invariably the case that the most closely
allied species are found in the same locality or in closely
adjoining localities, and that therefore the natural sequence of
the species by affinity is also geographical.

(4) In countries of a similar climate, but separated by a wide sea
or lofty mountains, the families, genera and species of the one
are often represented by closely allied families, genera and
species peculiar to the other.

GEOLOGY

(5) The distribution of the organic world in time is very similar
to its present distribution in space.

(6) Most of the larger and some of the smaller groups extend
through several geological periods.

(7) In each period, however, there are peculiar groups, found
nowhere else, and extending through one or several formations.

(8) Species of one genus, or genera of one family, occurring in
the same geological time are more closely allied than those
separated in time.

(9) As generally in geography no species or genus occurs in two
very distant localities without being also found in intermediate
places, so in geology the life of a species or genus has not been
interrupted. In other words, no group or species has come into
existence twice.

(10) The following law may be deduced from these facts: _Every
species has come into existence coincident both in time and space
with a pre-existing closely allied species_.

This law agrees with, explains and illustrates all the facts
connected with the following branches of the subject: 1st, the
system of natural affinities; 2nd, the distribution of animals and
plants in space; 3rd, the same in time, including all the
phenomena of representative groups, and those which Prof. Forbes
supposed to manifest polarity; 4th, the phenomena of rudimentary
organs. We will briefly endeavour to show its bearing upon each of
these.

If [this] law be true, it follows that the natural series of
affinities will also represent the order in which the several
species came into existence, each one having had for its immediate
antetype a clearly allied species existing at the time of its
origin.... If two or more species have been independently formed
on the plan of a common antetype, then the series of affinities
will be compound, and can only be represented by a forked or
many-branched line.... Sometimes the series of affinities can be
well represented for a space by a direct progression from species
to species or from group to group, but it is generally found
impossible so to continue. There constantly occur two or more
modifications of an organ or modifications of two distinct organs,
leading us on to two distinct series of species, which at length
differ so much from each other as to form distinct genera or
families. These are the parallel series or representative groups
of naturalists, and they often occur in different countries, or
are found fossil in different formations.... We thus see how
difficult it is to determine in every case whether a given
relation is an analogy or an affinity, for it is evident that as
we go back along the parallel or divergent series, towards the
common antetype, the analogy which existed between the two groups
becomes an affinity.... Again, if we consider that we have only
the fragments of this vast system, the stems and main branches
being represented by extinct species of which we have no
knowledge, while a vast mass of limbs and boughs and minute twigs
and scattered leaves is what we have to place in order, and
determine the true position each originally occupied with regard
to the others, the whole difficulty of the true Natural System of
classification becomes apparent to us.

We shall thus find ourselves obliged to reject all those systems
of classification which arrange species or groups in circles, as
well as those which fix a definite number for the division of each
group.... We have ... never been able to find a case in which the
circle has been closed by a direct affinity. In most cases a
palpable analogy has been substituted, in others the affinity is
very obscure or altogether doubtful....

If we now consider the geographical distribution of animals and
plants upon the earth, we shall find all the facts beautifully in
accordance with, and readily explained by, the present hypothesis.
A country having species, genera, and whole families peculiar to
it will be the necessary result of its having been isolated for a
long period, sufficient for many series of species to have been
created on the type of pre-existing ones, which, as well as many
of the earlier-formed species, have become extinct, and made the
groups appear isolated....

Such phenomena as are exhibited by the Galapagos Islands, which
contain little groups of plants and animals peculiar to
themselves, but most nearly allied to those of South America, have
not hitherto received any, even a conjectural explanation. The
Galapagos are a volcanic group of high antiquity and have probably
never been more closely connected with the continent than they are
at present.

He then proceeds at some length to explain how the Galapagos must have been at first "peopled ... by the action of winds and currents," and that the modified prototypes remaining are the "new species" which have been "created in each on the plan of the pre-existing ones." This is followed by a graphic sketch of the general effect of volcanic and other action as affecting the distribution of species, and the exact form in which they are found, even fishes giving "evidence of a similar kind: each great river [having] its peculiar genera, and in more extensive genera its groups of closely allied species."

After stating a number of practical examples he continues:

The question forces itself upon every thinking mind--Why are these
things so? They could not be as they are, had no law regulated
their creation and dispersion. The law here enunciated not merely
explains, but necessitates the facts we see to exist, while the
vast and long-continued geological changes of the earth readily
account for the exceptions and apparent discrepancies that here
and there occur. The writer's object in putting forward his views
in the present imperfect manner is to submit them to the tests of
other minds, and to be made aware of all the facts supposed to be
inconsistent with them. As his hypothesis is one which claims
acceptance solely as explaining and connecting facts which exist
in nature, he expects facts alone to be brought forward to
disprove it, not _a priori_ arguments against its probability.

He then refers to some of the geological "principles" expounded by Sir Charles Lyell on the "extinction of species," and follows this up by saying:

To discover how the extinct species have from time to time been
replaced by new ones down to the very latest geological period, is
the most difficult, and at the same time the most interesting,
problem in the natural history of the earth. The present inquiry,
which seeks to eliminate from known facts a law which has
determined, to a certain degree, what species could and did appear
at a given epoch, may, it is hoped, be considered as one step in
the right direction towards a complete solution of it.... Admitted
facts seem to show ... a general, but not a detailed
progression.... It is, however, by no means difficult to show
that a real progression in the scale of organisation is perfectly
consistent with all the appearances, and even with apparent
retrogression should such occur.

Using once more the analogy of a branching tree to illustrate the natural arrangement of species and their successive creation, he clearly shows how "apparent retrogression may be in reality a progress, though an interrupted one"; as "when some monarch of the forest loses a limb, it may be replaced by a feeble and sickly substitute." As an instance he mentions the Mollusca, which at an early period had reached a high state of development of forms and species, while in each succeeding age modified species and genera replaced the former ones which had become extinct, and "as we approach the present era but few and small representatives of the group remain, while the Gasteropods and Bivalves have acquired an immense preponderance." In the long series of changes the earth had undergone, the process of peopling it with organic beings had been continually going on, and whenever any of the higher groups had become nearly or quite extinct, the lower forms which better resisted the modified physical conditions served as the antetype on which to found new races. In this manner alone, it was believed, could the representative groups of successive periods, and the risings and fallings in the scale of organisations, be in every case explained.

Again, attending to a recent article by Prof. Forbes, he points out certain inaccuracies and how they may be proved to be so; and continues:

We have no reason for believing that the number of species on the
earth at any former period was much less than at present; at all
events the aquatic portion, with which the geologists have most
acquaintance, was probably often as great or greater. Now we know
that there have been many complete changes of species, new sets of
organisms have many times been introduced in place of old ones
which have become extinct, so that the total amount which have
existed on the earth from the earliest geological period must have
borne about the same proportion to those now living as the whole
human race who have lived and died upon the earth to the
population at the present time.... Records of vast geological
periods are entirely buried beneath the ocean ... beyond our
reach. Most of the gaps in the geological series may thus be
filled up, and vast numbers of unknown and unimaginable animals
which might help to elucidate the affinities of the numerous
isolated groups which are a perpetual puzzle to the zoologist may
be buried there, till future revolutions may raise them in turn
above the water, to afford materials for the study of whatever
race of intelligent beings may then have succeeded us. These
considerations must lead us to the conclusion that our knowledge
of the whole series of the former inhabitants of the earth is
necessarily most imperfect and fragmentary--as much as our
knowledge of the present organic world would be, were we forced to
make our collections and observations only in spots equally
limited in area and in number with those actually laid open for
the collection of fossils.... The hypothesis of Prof. Forbes is
essentially one that assumes to a great extent the _completeness_
of our knowledge of the _whole series_ of organic beings which
have existed on earth.... The hypothesis put forward in this paper
depends in no degree upon the completeness of our knowledge of the
former condition of the organic world, but takes what facts we
have as fragments of a vast whole, and deduces from them something
of the nature and proportion of that whole which we can never know
in detail....

Another important series of facts, quite in accordance with, and
even necessary deductions from, the law now developed, are those
of _rudimentary organs_. That these really do exist, and in most
cases have no special function in the animal economy, is admitted
by the first authorities in comparative anatomy. The minute limbs
hidden beneath the skin in many of the snake-like lizards, the
anal hooks of the boa constrictor, the complete series of jointed
finger-bones in the paddle of the manatee and the whale, are a few
of the most familiar instances. In botany a similar class of facts
has been long recognised. Abortive stamens, rudimentary floral
envelope and undeveloped carpels are of the most frequent
occurrence. To every thoughtful naturalist the question must
arise, What are these for? What have they to do with the great
laws of creation? Do they not teach us something of the system of
nature? If each species has been created independently, and
without any necessary relation with pre-existing species, what do
these rudiments, these apparent imperfections, mean? There must be
a cause for them; they must be the necessary result of some great
natural law. Now, if ... the great law which has regulated the
peopling of the earth with animal and vegetable life is, that
every change shall be gradual; that no new creature shall be
formed widely different from anything before existing; that in
this, as in everything else in nature, there shall be gradation
and harmony--then these rudimentary organs are necessary and are
an essential part of the system of nature. Ere the higher
vertebrates were formed, for instance, many steps were required,
and many organs had to undergo modifications from the rudimental
condition in which only they had as yet existed.... Many more of
these modifications should we behold, and more complete series of
them, had we a view of all the forms which have ceased to live.
The great gaps that exist ... would be softened down by
intermediate groups, and the whole organic world would be seen to
be an unbroken and harmonious system.

The article, in which we can see a great generalisation struggling to be born, ends thus:

It has now been shown, though most briefly and imperfectly, how
the law that "every species has come into existence coincident
both in time and space with a pre-existing closely allied
species," connects together and renders intelligible a vast number
of independent and hitherto unexplained facts. The natural system
of arrangement of organic beings, their geographical distribution,
their geological sequence, the phenomena of representative and
substituted groups in all their modifications, and the most
singular peculiarities of anatomical structure, are all explained
and illustrated by it, in perfect accordance with the vast mass of
facts which the researches of modern naturalists have brought
together, and, it is believed, not materially opposed to any of
them. It also claims a superiority over previous hypotheses, on
the ground that it not merely explains but necessitates what
exists. Granted the law, and many of the most important facts in
nature could not have been otherwise, but are almost as necessary
deductions from it as are the elliptic orbits of the planets from
the law of gravitation.

Some time after the appearance of this article, Wallace was informed by his friend and agent, Mr. Stevens, that several naturalists had expressed regret that he was "theorising," when what "was wanted was to collect more facts." Apart from this the only recognition which reached him in his remote solitude was a remark in an approving letter from Darwin (_see_ p. 129).

As Wallace wrote nothing further of importance until the second essay which more fully disclosed his view of the origin of species, we will now briefly trace the growth of the theory of Natural Selection up to 1858, as it came to Darwin.

It is well known that during Darwin's voyage in the _Beagle_ he was deeply impressed by discovering extinct armadillo-like fossil forms in South America, the home of armadilloes, and by observing the relationship of the plants and animals of each island in the Galapagos group to those of the other islands and of South America, the nearest continent. These facts suggested evolution, and without evolution appeared to be meaningless.

Evolution and its motive cause were the problems which "haunted" him for the next twenty years. The first step towards a possible solution was the "opening of a notebook for facts in relation to the origin of species" in 1837, two years before the publication of his Journal. From the very commencement of his literary and scientific work, a rule rigidly adhered to was that of interspersing his main line of thought and research by reading books touching on widely diverging subjects; and it was thus, no doubt, that during October, 1838, he read "for amusement" Malthus's "Essay on Population"; not, as he himself affirms, with any definite idea as to its intimate bearing on the subject so near his heart. But the immediate result was that the idea of Natural Selection at once arose in his mind, and, in his own words, he "had a theory by which to work."

In May and June, 1842, during a visit to Maer and Shrewsbury, he wrote his first "pencil sketch of Species theory," but not until two years later (1844) did he venture to enlarge this to one of 230 folio pages, "a wonderfully complete presentation of the arguments familiar to us in the 'Origin.'"[19]

Already, in addition to the mass of facts collected, Darwin was busy with some of the experiments which he described in a letter to Sir Joseph Hooker (in 1855) as affording the latter a "good right to sneer, for they are so _absurd_, even in _my_ opinion, that I dare not tell you." While a sentence in another letter (dated 1849) throws a sidelight on all this preparatory work: "In your letter you wonder what 'ornamental poultry' has to do with barnacles; but do not flatter yourself that I shall not yet live to finish the barnacles, and then make a fool of myself on the subject of species, under which head ornamental poultry are very interesting."

Somewhere about this time (1842-44), Darwin, referring to the idea of Natural Selection which arose in his mind after reading Malthus on "Population" four years earlier, continues: "But at that time I overlooked one problem of great importance ... the tendency in organic beings descended from the same stock to diverge in character as they become modified ... and I can remember the very spot in the road, whilst in my carriage, when to my joy the solution occurred to me.... The solution, as I believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature."[20]

So convinced was he of the truth of his ideas as expressed in the 1844 MS., that immediately after its completion he wrote the memorable letter to Mrs. Darwin telling her what he would wish done regarding its publication in the event of his death.

It was probably about two years later (1846) that he first confided his completed work--up to that date--to Sir Joseph Hooker, and later to Sir Charles Lyell; refraining, however, except in general conversation with other scientists, from informing anyone of the progress he was making towards a positive solution of the problem. His attitude of mind and manner at this period is happily illustrated by Huxley, who, speaking of his early acquaintance with Darwin, says: "I remember in the course of my first interview with Darwin expressing my belief in the sharpness of the line of demarcation between natural groups and in the absence of transitional forms, with all the confidence of youth and imperfect knowledge. I was not aware, at that time, that he had then been many years brooding over the Species question; and the humorous smile which accompanied his gentle answer, that such was not altogether his view, long haunted and puzzled me."

Little did Charles Darwin dream that, only three years after this first MS. was written (in 1844), a youthful naturalist--known only as a surveyor at Neath--was deliberately pondering over the same issue, and writing to his only scientific friend on the subject. As, however, the different methods of thought by which they arrived at the same conclusion is so aptly related by Wallace himself, we will leave it for him to tell the story in its appointed place.[21]

In 1856, the year following the appearance of Wallace's essay in the _Annals and Magazine of Natural History_, both Hooker and Lyell urged Darwin to publish the result of his long and patient research. But he was still reluctant to do so, not having as yet satisfied himself with regard to certain conclusions which, he felt, must be stoutly maintained in face of the enormous amount of criticism which would arise immediately his theory was launched on the scientific world. And thus the event was postponed until the memorable year 1858.

Up to the year 1856 no correspondence had passed between Wallace and Darwin, so far, at least, as the former could remember, for he says, in a letter dated Frith Hill, Godalming, December 3, 1887 (written to Mr. A. Newton): "I had hardly heard of Darwin before going to the East, except as connected with the voyage of the _Beagle_.... I saw him _once_ for a few minutes in the British Museum before I sailed. Through Stevens, my agent, I heard that he wanted curious _varieties_ which he was studying. I _think_ I wrote about some varieties of ducks I had sent, and he must have written once to me.... But at that time I had not the remotest notion that he had already arrived at a definite theory--still less that it was the same as occurred to me, suddenly, in Ternate in 1858." It is clear, therefore, that the essay written at Sarawak formed the first real link with Darwin, although not fully recognised at the time. In May, 1857, Darwin wrote to Wallace: "I am much obliged for your letter ... and even still more by your paper in the _Annals_, a year or more ago. I can plainly see that we have thought much alike and to a certain extent have come to similar conclusions.... I agree to almost every word of your paper; and I dare say that you will agree with me that it is very rare to find oneself agreeing pretty closely with any theoretical paper." He concludes: "You have my very sincere and cordial good wishes for success of all kinds, and may all your theories succeed, except that on Oceanic Islands, on which subject I will do battle to the death."

The three years from 1855 to 1858 were for Wallace crowded with hard work, and perilous voyages by sea and hardships by land. January, 1858, found him at Amboyna, where, in all probability, he found a pile of long-delayed correspondence awaiting him, and among this a letter from Bates referring to the article which had appeared in print September, 1855. In reply he says: "To persons who have not thought much on the subject I fear my paper on the 'Succession of Species' will not appear so clear as it does to you. That paper is, of course, merely the announcement of the theory, not its development. I have prepared the plan and written portions of a work embracing the whole subject, and have endeavoured to prove in detail what I have as yet only indicated.... I have been much gratified by a letter from Darwin, in which he says that he agrees with 'almost every word' of my paper. He is now preparing his great work on 'Species and Varieties,' for which he has been preparing materials for twenty years. He may save me the trouble of writing more on my hypothesis, by proving that there is no difference in nature between the origin of species and of varieties; or he may give me trouble by arriving at another conclusion; but, at all events, his facts will be given for me to work upon. Your collections and my own will furnish most valuable material to illustrate and prove the universal application of the hypothesis. The connection between the succession of affinities and the geographical distribution of a group, worked out species by species, has never yet been shown as we shall be able to show it."

"This letter proves," writes Wallace,[22] "that at this time I had not the least idea of the nature of Darwin's proposed work nor of the definite conclusions he had arrived at, nor had I myself any expectations of a complete solution of the great problem to which my paper was merely the prelude. Yet less than two months later that solution flashed upon me, and to a large extent marked out a different line of work from that which I had up to this time anticipated.... In other parts of this letter I refer to the work I hoped to do myself in describing, cataloguing, and working out the distribution of my insects. I had in fact been bitten by the passion for species and their description, and if neither Darwin nor myself had hit upon 'Natural Selection,' I might have spent the best years of my life in this comparatively profitless work. But the new ideas swept all this away."

This letter was finished after his arrival at Ternate, and a few weeks later he was prostrated by a sharp attack of intermittent fever which obliged him to take a prolonged rest each day, owing to the exhausting hot and cold fits which rapidly succeeded one another.

The little bungalow at Ternate had now come to be regarded as "home" for it was here that he stored all his treasured collections, besides making it the goal of all his wanderings in the Archipelago. One can understand, therefore, that, in spite of the fever, there was a sense of satisfaction in the feeling that he was surrounded with the trophies of his arduous labours as a naturalist, and this passion for species and their descriptions being an ever-present speculation in his mind, his very surroundings would unconsciously conduce towards the line of thought which brought to memory the argument of "positive checks" set forth by Malthus in his "Principles of Population" (read twelve years earlier) as applied to savage and civilised races. "It then," he says, "occurred to me that these causes or their equivalents are continually acting in the case of animals also; and as animals usually breed much more rapidly than does mankind, the destruction every year from these causes must be enormous in order to keep down the numbers of each species, since they evidently do not increase regularly from year to year, as otherwise the world would have been densely crowded with those that breed most quickly.... Then it suddenly flashed upon me that this self-acting process would necessarily _improve the race_, because in every generation the inferior would inevitably be killed off and the superior would remain--that is, the _fittest would survive_. Then at once I seemed to see the whole effect of this, that when changes of land and sea, or of climate, or of food-supply, or of enemies occurred--and we know that such changes have always been taking place--and considering the amount of individual variation that my experience as a collector had shown me to exist, then it followed that all the changes necessary for the adaptation of the species to the changing conditions would be brought about; and as great changes in the environment are always slow, there would be ample time for the change to be effected by the survival of the best fitted in every generation. In this way every part of an animal's organism could be modified as required, and in the very process of this modification the unmodified would die out, and thus the _definite_ characters and the clear _isolation_ of each new species would be explained. The more I thought over it the more I became convinced that I had at length found the long-sought-for law of nature that solved the problem of the origin of species. For the next hour I thought over the deficiencies in the theories of Lamarck and of the author of the 'Vestiges,' and I saw that my new theory supplemented these views and obviated every important difficulty. I waited anxiously for the termination of my fit (of fever) so that I might at once make notes for a paper on the subject. The same evening I did this pretty fully, and on the two succeeding evenings wrote it out carefully in order to send it to Darwin by the next post, which would leave in a day or two."[23]

The story of the arrival of this letter at Down, and of the swift passage of events between the date on which Darwin received it and the reading of the "joint communications" before the Linnean Society, has been often told. But few, perhaps, have enjoyed the privilege of reading the account of this memorable proceeding as related by Sir Joseph Hooker at the celebration of the event held by the Linnean Society in 1908.

As, therefore, the correspondence (pp. 127-320) between Wallace and Darwin during a long series of years conveys many expressions of their mutual appreciation of each other's work in connection with the origin of species, it will avoid a possible repetition of these if we take a long leap forward and give the notable speeches made by Wallace, Sir Joseph Hooker, Sir E. Ray Lankester, and others at this historical ceremony, which have not been published except in the _Proceedings_ of the Society, now out of print.

The gathering was held on July 1, 1908, at the Institute of Civil Engineers, Great George Street, to celebrate the fiftieth anniversary of the joint communication made by Charles Darwin and Alfred Russel Wallace to the Linnean Society, "On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection." The large gathering included the President, Dr. Dukinfield H. Scott, distinguished representatives of many scientific Societies and Universities, the Danish and Swedish Ministers, and a representative from the German Embassy. Most of the members of Dr. Wallace's and Mr. Darwin's family were also present.[24] The President opened with some explanatory observations, and then invited Wallace to come forward in order to receive the first Darwin-Wallace Medal. In presenting it he said:

Dr. Alfred Russel Wallace,--We rejoice that we are so happy as to
have with us to-day the survivor of the two great naturalists
whose crowning work we are here to commemorate.

Your brilliant work in natural history and geography, and as one
of the founders of the theory of Evolution by Natural Selection,
is universally honoured and has often received public recognition,
as in the awards of the Darwin and Royal Medals of the Royal
Society, and of our Medal in 1892.

To-day, in asking you to accept the first Darwin-Wallace Medal, we
are offering you of your own, for it is you, equally with your
great colleague, who created the occasion we celebrate.

There is nothing in the history of science more delightful or more
noble than the story of the relations between yourself and Mr.
Darwin, as told in the correspondence now so fully published--the
story of a generous rivalry in which each discoverer strives to
exalt the claims of the other. We know that Mr. Darwin wrote
(April 6th, 1859): "You cannot tell how much I admire your spirit
in the manner in which you have taken all that was done about
publishing our papers. I had actually written a letter to you
stating that I would not publish anything before you had
published." Then came the letters of Hooker and Lyell, leading to
the publication of the joint papers which they communicated.

You, on your side, always gave the credit to him, and
underestimated your own position as the co-discoverer. I need only
refer to your calling your great exposition of the joint theory
"Darwinism," as the typical example of your generous emphasising
of the claims of your illustrious fellow-worker.

It was a remarkable and momentous coincidence that both you and he
should have independently arrived at the idea of Natural Selection
after reading Malthus's book, and a most happy inspiration that
you should have selected Mr. Darwin as the naturalist to whom to
communicate your discovery. That theory, in spite of changes in
the scientific fashion of the moment, you have always
unflinchingly maintained, and still uphold as unshaken by all
attacks.

Like Mr. Darwin, you, if I may say so, are above all a naturalist,
a student and lover of living animals and plants, as shown in
later years by your enthusiasm and success in gardening. It is to
such men, those who have learnt the ways of Nature, as Nature
really is in the open, to whom your doctrine of Natural Selection
specially appeals, and therein lies its great and lasting
strength.

Finally, you must allow me to allude to the generous interest you
have always shown, and continue to show, in the careers of
younger men who are endeavouring to follow in your steps.

I ask you, Dr. Wallace, to accept this Medal, struck in your
honour and in that of the great work inaugurated fifty years ago
by Mr. Darwin and yourself.

Wallace began his reply by thanking the Council of the Society for the Honour they had done him, and then proceeded:

Since the death of Darwin, in 1882, I have found myself in the
somewhat unusual position of receiving credit and praise from
popular writers under a complete misapprehension of what my share
in Darwin's work really amounted to. It has been stated (not
unfrequently) in the daily and weekly press, that Darwin and
myself discovered "Natural Selection" simultaneously, while a more
daring few have declared that I was _the first_ to discover it,
and I gave way to Darwin!

In order to avoid further errors of this kind (which this
Celebration may possibly encourage), I think it will be well to
give the actual facts as simply and clearly as possible.

The _one fact_ that connects me with Darwin, and which, I am happy
to say, has never been doubted, is that the idea of what is now
termed "natural selection" or "survival of the fittest," together
with its far-reaching consequences, occurred to us
_independently_, and was first jointly announced before this
Society fifty years ago.

But, what is often forgotten by the Press and the public is, that
the idea occurred to Darwin in 1838, nearly twenty years earlier
than to myself (in February, 1858); and that during the whole of
that twenty years he had been laboriously collecting evidence from
the vast mass of literature of biology, of horticulture, and of
agriculture; as well as himself carrying out ingenious experiments
and original observations, the extent of which is indicated by the
range of subjects discussed in his "Origin of Species," and
especially in that wonderful storehouse of knowledge, his "Animals
and Plants under Domestication," almost the whole materials for
which work had been collected, and to a large extent systematised,
during that twenty years.

So far back as 1844, at a time when I had hardly thought of any
serious study of nature, Darwin had written an outline of his
views, which he communicated to his friends Sir Charles Lyell and
Dr. (now Sir Joseph) Hooker. The former strongly urged him to
publish an abstract of his theory as soon as possible, lest some
other person might precede him; but he always refused till he had
got together the whole of the materials for his intended great
work. Then, at last, Lyell's prediction was fulfilled, and,
without any apparent warning, my letter, with the enclosed essay,
came upon him, like a thunderbolt from a cloudless sky! This
forced him to what he considered a premature publicity, and his
two friends undertook to have our two papers read before this
Society.

How different from this long study and preparation--this
philosophical caution--this determination not to make known his
fruitful conception till he could back it up by overwhelming
proofs--was my own conduct.

The idea came to me as it had come to Darwin, in a sudden flash of
insight; it was thought out in a few hours--was written down with
such a sketch of its various applications and developments as
occurred to me at the moment--then copied on thin letter paper and
sent off to Darwin--all within one week. _I_ was then (as often
since) the "young man in a hurry": _he_, the painstaking and
patient student seeking ever the full demonstration of the truth
that he had discovered, rather than to achieve immediate personal
fame.

Such being the actual facts of the case, I should have had no
cause for complaint if the respective shares of Darwin and myself
in regard to the elucidation of Nature's method of organic
development had been henceforth estimated as being, roughly,
proportional to the time we had each bestowed upon it when it was
thus first given to the world--that is to say, as twenty years is
to one week. For, he had already made it his own. If the
persuasion of his friends had prevailed with him, and he had
published his theory after ten years'--fifteen years'--or even
eighteen years' elaboration of it--_I_ should have had no part in
it whatever, and _he_ would have been at once recognised as the
sole and undisputed discoverer and patient investigator of this
great law of "Natural Selection" in all its far-reaching
consequences.

It was really a singular piece of good luck that gave to me any
share whatever in the discovery. During the first half of the
nineteenth century (and even earlier) many great biological
thinkers and workers had been pondering over the problem and had
even suggested ingenious but inadequate solutions. Some of these
men were among the greatest intellects of our time, yet, till
Darwin, all had failed; and it was only Darwin's extreme desire to
perfect his work that allowed me to come in, as a very bad second,
in the truly Olympian race in which all philosophical biologists,
from Buffon and Erasmus Darwin to Richard Owen and Robert
Chambers, were more or less actively engaged.

And this brings me to the very interesting question: Why did so
many of the greatest intellects fail, while Darwin and myself hit
upon the solution of this problem--a solution which this
Celebration proves to have been (and still to be) a satisfying one
to a large number of those best able to form a judgment on its
merits? As I have found what seems to me a good and precise answer
to this question, and one which is of some psychological interest,
I will, with your permission, briefly state what it is.

On a careful consideration, we find a curious series of
correspondences, both in mind and in environment, which led Darwin
and myself, alone among our contemporaries, to reach identically
the same theory.

First (and most important, as I believe), in early life both
Darwin and myself became ardent beetle-hunters. Now there is
certainly no group of organisms that so impresses the collector by
the almost infinite number of its specific forms, the endless
modifications of structure, shape, colour, and surface-markings
that distinguish them from each other, and their innumerable
adaptations to diverse environments. These interesting features
are exhibited almost as strikingly in temperate as in tropical
regions, our own comparatively limited island-fauna possessing
more than 3,000 species of this one order of insects.

Again, both Darwin and myself had what he terms "the mere passion
for collecting," not that of studying the minutiæ of structure,
either internal or external. I should describe it rather as an
intense interest in the variety of living things--the variety that
catches the eye of the observer even among those which are very
much alike, but which are soon found to differ in several distinct
characters.

Now it is this superficial and almost child-like interest in the
outward forms of living things which, though often despised as
unscientific, happened to be _the only one_ which would lead us
towards a solution of the problem of species. For Nature herself
distinguishes her species by just such characters--often
exclusively so, always in some degree--very small changes in
outline, or in the proportions of appendages--as give a quite
distinct and recognisable facies to each, often aided by slight
peculiarities in motion or habit; while in a larger number of
cases differences of surface-texture, of colour, or in the details
of the same general scheme of colour-pattern or of shading, give
an unmistakable individuality to closely allied species.

It is the constant search for and detection of these often
unexpected differences between very similar creatures that gives
such an intellectual charm and fascination to the mere collection
of these insects; and when, as in the case of Darwin and myself,
the collectors were of a speculative turn of mind, they were
constantly led to think upon the "why" and the "how" of all this
wonderful variety in nature--this overwhelming and, at first
sight, purposeless wealth of specific forms among the very
humblest forms of life.

Then, a little later (and with both of us almost accidentally) we
became travellers, collectors, and observers, in some of the
richest and most interesting portions of the earth; and we thus
had forced upon our attention all the strange phenomena of local
and geographical distribution, with the numerous problems to
which they give rise. Thenceforward our interest in the great
mystery of _how_ species came into existence was intensified,
and--again to use Darwin's expression--"haunted" us.

Finally, both Darwin and myself, at the critical period when our
minds were freshly stored with a considerable body of personal
observation and reflection bearing upon the problem to be solved,
had our attention directed to the system of _positive checks_ as
expounded by Malthus in his "Principles of Population." The effect
of that was analogous to that of friction upon the specially
prepared match, producing that flash of insight which led us
immediately to the simple but universal law of the "survival of
the fittest," as the long-sought _effective_ cause of the
continuous modification and adaptations of living things.