I have called attention in footnotes to many points in which the _Origin_ agrees with the _Foundations_. One of the most interesting is the final sentence, practically the same in the Essays of 1842 and 1844, and almost identical with the concluding words of the _Origin_. I have elsewhere pointed out{35} that the ancestry of this eloquent pa.s.sage may be traced one stage further back,--to the Note Book of 1837. I have given this sentence as an appropriate motto for the _Foundations_ in its character of a study of general laws. It will be remembered that a corresponding motto from Whewell"s _Bridgewater Treatise_ is printed opposite the t.i.tle-page of the _Origin of Species_.
{35} _Life and Letters_, ii. p. 9.
Mr Huxley who, about the year 1887, read the Essay of 1844, remarked that "much more weight is attached to the influence of external conditions in producing variation and to the inheritance of acquired habits than in the _Origin_." In the _Foundations_ the effect of conditions is frequently mentioned, and Darwin seems to have had constantly in mind the need of referring each variation to a cause. But I gain the impression that the slighter prominence given to this view in the _Origin_ was not due to change of opinion, but rather because he had gradually come to take this view for granted; so that in the scheme of that book, it was overshadowed by considerations which then seemed to him more pressing. With regard to the inheritance of acquired characters I am not inclined to agree with Huxley. It is certain that the _Foundations_ contains strong recognition of the importance of germinal variation, that is of external conditions acting indirectly through the "reproductive functions." He evidently considered this as more important than the inheritance of habit or other acquired peculiarities.
Another point of interest is the weight he attached in 1842-4 to "sports" or what are now called "mutations." This is I think more prominent in the _Foundations_ than in the first edition of the _Origin_, and certainly than in the fifth and sixth editions.
Among other interesting points may be mentioned the "good effects of crossing" being "possibly a.n.a.logous to good effects of change in condition,"--a principle which he upheld on experimental grounds in his _Cross and Self-Fertilisation_ in 1876.
In conclusion, I desire to express my thanks to Mr Wallace for a footnote he was good enough to supply: and to Professor Bateson, Sir W.
Thiselton-Dyer, Dr Gadow, Professor Judd, Dr Marr, Col. Prain and Dr Stapf for information on various points. I am also indebted to Mr Rutherford, of the University Library, for his careful copy of the ma.n.u.script of 1842.
CAMBRIDGE,
_June 9, 1909._
PART I.
-- I. An individual organism placed under new conditions [often] sometimes varies in a small degree and in very trifling respects such as stature, fatness, sometimes colour, health, habits in animals and probably disposition. Also habits of life develope certain parts. Disuse atrophies. [Most of these slight variations tend to become hereditary.]
When the individual is multiplied for long periods by buds the variation is yet small, though greater and occasionally a single bud or individual departs widely from its type (example){36} and continues steadily to propagate, by buds, such new kind.
{36} Evidently a memorandum that an example should be given.
When the organism is bred for several generations under new or varying conditions, the variation is greater in amount and endless in kind [especially{37} holds good when individuals have long been exposed to new conditions]. The nature of the external conditions tends to effect some definite change in all or greater part of offspring,--little food, small size--certain foods harmless &c. &c. organs affected and diseases--extent unknown. A certain degree of variation (Muller"s twins){38} seems inevitable effect of process of reproduction. But more important is that simple generation, especially under new conditions [when no crossing] infinite variation and not direct effect of external conditions, but only in as much as it affects the reproductive functions{39}. There seems to be no part (_beau ideal_ of liver){40} of body, internal or external, or mind or habits, or instincts which does not vary in some small degree and [often] some to a great amount.{37} The importance of exposure to new conditions for several generations is insisted on in the _Origin_, Ed. i. p. 7, also p.
131. In the latter pa.s.sage the author guards himself against the a.s.sumption that variations are "due to chance," and speaks of "our ignorance of the cause of each particular variation." These statements are not always remembered by his critics.
{38} Cf. _Origin_, Ed. i. p. 10, vi. p. 9, "Young of the same litter, sometimes differ considerably from each other, though both the young and the parents, as Muller has remarked, have apparently been exposed to exactly the same conditions of life."
{39} This is paralleled by the conclusion in the _Origin_, Ed. i.
p. 8, that "the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception."
{40} The meaning seems to be that there must be some variability in the liver otherwise anatomists would not speak of the "beau ideal"
of that organ.
[All such] variations [being congenital] or those very slowly acquired of all kinds [decidedly evince a tendency to become hereditary], when not so become simple variety, when it does a race. Each{41} parent transmits its peculiarities, therefore if varieties allowed freely to cross, except by the _chance_ of two characterized by same peculiarity happening to marry, such varieties will be constantly demolished{42}.
All bis.e.xual animals must cross, hermaphrodite plants do cross, it seems very possible that hermaphrodite animals do cross,--conclusion strengthened: ill effects of breeding in and in, good effects of crossing possibly a.n.a.logous to good effects of change in condition {43}.
{41} The position of the following pa.s.sage is uncertain. "If individuals of two widely different varieties be allowed to cross, a third race will be formed--a most fertile source of the variation in domesticated animals. If freely allowed, the characters of pure parents will be lost, number of races thus but differences besides the . But if varieties differing in very slight respects be allowed to cross, such small variation will be destroyed, at least to our senses,--a variation [clearly]just to be distinguished by long legs will have offspring not to be so distinguished. Free crossing great agent in producing uniformity in any breed. Introduce tendency to revert to parent form."
{42} The swamping effect of intercrossing is referred to in the _Origin_, Ed. i. p. 103, vi. p. 126.
{43} A discussion on the intercrossing of hermaphrodites in relation to Knight"s views occurs in the _Origin_, Ed. i. p. 96, vi. p. 119. The parallelism between crossing and changed conditions is briefly given in the _Origin_, Ed. i. p. 267, vi. p. 391, and was finally investigated in _The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom_, 1876.
Therefore if in any country or district all animals of one species be allowed freely to cross, any small tendency in them to vary will be constantly counteracted. Secondly reversion to parent form--a.n.a.logue of _vis medicatrix_{44}. But if man selects, then new races rapidly formed,--of late years systematically followed,--in most ancient times often practically followed{45}. By such selection make race-horse, dray-horse--one cow good for tallow, another for eating &c.--one plant"s good lay in leaves another in fruit &c. &c.: the same plant to supply his wants at different times of year. By former means animals become adapted, as a direct effect to a cause, to external conditions, as size of body to amount of food. By this latter means they may also be so adapted, but further they may be adapted to ends and pursuits, which by no possibility can affect growth, as existence of tallow-chandler cannot tend to make fat. In such selected races, if not removed to new conditions, and preserved from all cross, after several generations become very true, like each other and not varying. But man{46} selects only what is useful and curious--has bad judgment, is capricious,--grudges to destroy those that do not come up to his pattern,--has no [knowledge] power of selecting according to internal variations,--can hardly keep his conditions uniform,--[cannot] does not select those best adapted to the conditions under which form lives, but those most useful to him. This might all be otherwise.{44} There is an article on the _vis medicatrix_ in Brougham"s _Dissertations_, 1839, a copy of which is in the author"s library.
{45} This is the cla.s.sification of selection into methodical and unconscious given in the _Origin_, Ed. i. p. 33, vi. p. 38.
{46} This pa.s.sage, and a similar discussion on the power of the Creator (p. 6), correspond to the comparison between the selective capacities of man and nature, in the _Origin_, Ed. i. p. 83, vi. p.
102.
-- II. Let us see how far above principles of variation apply to wild animals.
Wild animals vary exceedingly little--yet they are known as individuals{47}. British Plants, in many genera number quite uncertain of varieties and species: in sh.e.l.ls chiefly external conditions{48}.
Primrose and cowslip. Wild animals from different [countries can be recognized]. Specific character gives some organs as varying. Variations a.n.a.logous in kind, but less in degree with domesticated animals--chiefly external and less important parts.
{47} i.e. they are individually distinguishable.
{48} See _Origin_, Ed. i. p. 133, vi. p. 165.
Our experience would lead us to expect that any and every one of these organisms would vary if taken away and placed under new conditions. Geology proclaims a constant round of change, bringing into play, by every possible change of climate and the death of pre-existing inhabitants, endless variations of new conditions. These generally very slow, doubtful though how far the slowness would produce tendency to vary. But Geolog show change in configuration which, together with the accidents of air and water and the means of transportal which every being possesses, must occasionally bring, rather suddenly, organism to new conditions and expose it for several generations. Hence we should expect every now and then a wild form to vary{49}; possibly this may be cause of some species varying more than others.{49} When the author wrote this sketch he seems not to have been so fully convinced of the general occurrence of variation in nature as he afterwards became. The above pa.s.sage in the text possibly suggests that at this time he laid more stress on _sports_ or _mutations_ than was afterwards the case.
According to nature of new conditions, so we might expect all or majority of organisms born under them to vary in some definite way.
Further we might expect that the mould in which they are cast would likewise vary in some small degree. But is there any means of selecting those offspring which vary in the same manner, crossing them and keeping their offspring separate and thus producing selected races: otherwise as the wild animals freely cross, so must such small heterogeneous varieties be constantly counter-balanced and lost, and a uniformity of character [kept up] preserved. The former variation as the direct and necessary effects of causes, which we can see can act on them, as size of body from amount of food, effect of certain kinds of food on certain parts of bodies &c. &c.; such new varieties may then become adapted to those external [natural] agencies which act on them. But can varieties be produced adapted to end, which cannot possibly influence their structure and which it is absurd to look up trees, miseltoe, . But if every part of a plant or animal was to vary , and if a being infinitely more sagacious than man (not an omniscient creator) during thousands and thousands of years were to select all the variations which tended towards certain ends ([or were to produce causes which tended to the same end]), for instance, if he foresaw a canine animal would be better off, owing to the country producing more hares, if he were longer legged and keener sight,--greyhound produced{51}. If he saw that aquatic like most plants is occasionally visited by bees &c.: if that plant"s seed were occasionally eaten by birds and were then carried on to rotten trees, he might select trees with fruit more agreeable to such birds as perched, to ensure their being carried to trees; if he perceived those birds more often dropped the seeds, he might well have selected a bird who would rotten trees or [gradually select plants which had proved to live on less and less rotten trees]. Who, seeing how plants vary in garden, what blind foolish man has done{52} in a few years, will deny an all-seeing being in thousands of years could effect (if the Creator chose to do so), either by his own direct foresight or by intermediate means,--which will represent the creator of this universe. Seems usual means. Be it remembered I have nothing to say about life and mind and _all_ forms descending from one common type{53}. I speak of the variation of the existing great divisions of the organised kingdom, how far I would go, hereafter to be seen.{50} The author may possibly have taken the case of the woodp.e.c.k.e.r from Buffon, _Histoire Nat. des Oiseaux_, T. vii. p. 3, 1780, where however it is treated from a different point of view. He uses it more than once, see for instance _Origin_, Ed. i. pp. 3, 60, 184, vi. pp. 3, 76, 220. The pa.s.sage in the text corresponds with a discussion on the woodp.e.c.k.e.r and the mistletoe in _Origin_, Ed. i.
p. 3, vi. p. 3.
{51} This ill.u.s.tration occurs in the _Origin_, Ed. i. pp. 90, 91, vi. pp. 110, 111.
{52} See _Origin_, Ed. i. p. 83, vi. p. 102, where the word _Creator_ is replaced by _Nature_.
{53} Note in the original. "Good place to introduce, saying reasons hereafter to be given, how far I extend theory, say to all mammalia--reasons growing weaker and weaker."
Before considering whether be any natural means of selection, and secondly (which forms the 2nd Part of this sketch) the far more important point whether the characters and relations of animated are such as favour the idea of wild species being races descended from a common stock, as the varieties of potato or dahlia or cattle having so descended, let us consider probable character of [selected races] wild varieties._Natural Selection._ De Candolle"s war of nature,--seeing contented face of nature,--may be well at first doubted; we see it on borders of perpetual cold{54}. But considering the enormous geometrical power of increase in every organism and as every country, in ordinary cases must be stocked to full extent, reflection will show that this is the case. Malthus on man,--in animals no moral [check] restraint --they breed in time of year when provision most abundant, or season most favourable, every country has its seasons,--calculate robins,--oscillating from years of destruction{55}. If proof were wanted let any singular change of climate here , how astoundingly some tribes increase, also introduced animals{56}, the pressure is always ready,--capacity of alpine plants to endure other climates,--think of endless seeds scattered abroad,--forests regaining their percentage{57},--a thousand wedges{58} are being forced into the oeconomy of nature. This requires much reflection; study Malthus and calculate rates of increase and remember the resistance,--only periodical.{54} See _Origin_, Ed. i. pp. 62, 63, vi. p. 77, where similar reference is made to De Candolle; for Malthus see _Origin_, p. 5.
{55} This may possibly refer to the amount of destruction going on.
See _Origin_, Ed. i. p. 68, vi. p. 84, where there is an estimate of a later date as to death-rate of birds in winter. "Calculate robins" probably refers to a calculation of the rate of increase of birds under favourable conditions.
{56} In the _Origin_, Ed. i. pp. 64, 65, vi. p. 80, he instances cattle and horses and certain plants in S. America and American species of plants in India, and further on, as unexpected effects of changed conditions, the enclosure of a heath, and the relation between the fertilisation of clover and the presence of cats (_Origin_, Ed. i. p. 74, vi. p. 91).