"SPIN NES propaga es shit SPSS NERD AB CONT RENMEI UNIVERSITY LIBRARY 3 | ThA Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024753950 DARWINISM STATED BY DARWIN HIMSELF. - CHARACTERISTIC PASSAGES FROM THE WRITINGS OF CHARLES DARWIN. SELECTED AND ARRANGED BY NATHAN SHEPPARD, AUTHOR OF “SHUT UP IN PARIS,” EDITOR OF “TIE DICKENS READER,” “OHARACTER READINGS FROM GEORGE ELIOT,” AND “GEORGE ELIOT'S RSSAY¥s.” “ There is grandegr in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into onc ; and that, while this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been and are being evolved.”—The Origin of Species, page 429. NEW YORK: ; D. APPLETON AND COMPANY, 1,8, anp 5 BOND STREET. 1884, 365 a Cr far Riemer ae § ae WORE TY. 4&3 o> A 337 su Faria - Coprzicut, 1884, By D. APPLETON AND COMPANY. PREFACE. WHILE these selections can not but be useful to those who are perfectly familiar with the writings of Darwin, they are designed especially for those who know little, or nothing, about his line of research and argument, and yet would like to obtain a general idea of it in a form which shall be at once authentic, brief, and inex- pensive. This volume contains, of course, only an outline of the contents of the twelve volumes from which it is compiled, and for which it is by no means intended as a substitute. It will, on the contrary, we should hope, create an appetite which can be satisfied only by a care- ful reading of the works themselves. Darwin’s repetitions, necessitated by his method of investigation and publication, and his unexampled can- dor in controversy, haye been something of an embar- rassment in the classification of these passages; so that we have been obliged in some instances to sacrifice con- tinuity to perspicuity. But, as one object of this book is to correct misrepresentations by giving Darwin’s views iy PREFACE. in his own language, some of his own repetitions must be given also, in order to leave no doubt as to precisely what he said and did not say. It will probably be a long while before the dispute over the theory that he advocated will cease, but there is certainly no excuse for a difference of opinion with regard to the language that he used, and the meaning he attached to it. That language and that meaning will be found in these pages. Darwinism stated by its opponents is one thing, Darwinism stated by Darwin himself will be found to be quite another thing, for, to use his own exclamation, ‘‘oreat is the power of steady misrepresentation !” The order followed in the arrangement of these ex- tracts is not that of the books, but the one naturally suggested by our plan, which is designed to conduct the reader through the vegetable up to the animal kingdom, and up from the lowest to the highest animal, man, “‘the wonder and glory of the universe.” The references are to the American edition of Dar- win’s works published by D. Appleton & Co., New York. It is no part of our purpose to discuss the theory expounded here, but we can not refrain from joining in the general expression of admiration for its illustrious expounder. Lord Derby says, ‘‘He was one of half a dozen men of this century who will be remembered a century hence”; and yet his friends were ‘“‘more im- pressed with the dignified simplicity of his nature than by the great work he had done.” Professor Huxley PREFACE. v compares him to Socrates in wisdom and humility ; and there could be no better authority than Mr. A. R. Wal- lace for the statement that ‘‘ there are none to stand beside him as equals in the whole domain of science.” He has been extolled, since his death, by a host of re- ligious leaders in press and pulpit (some of whose utter- ances will be found on another page), and we concur with them in the opinion that science never had a champion whose temper and behavior were more nearly in accord with the practical injunctions of the Christian religion. Whatever we or any one may think of Dar- win’s scientific theories, no one can gainsay the value of his personal example, and few can be so prejudiced as to resist the fascination that will always be felt at the mention of his name. New Yors, February 1, 1884. INTRODUCTORY PASSAGES QUOTED BY DARWIN IN HIS “ORIGIN OF SPECIES.” “Bor with regard to the material world, we can at least go so far as this—we can perceive that events are brought about not by insulated interpositions of divine power, exerted in each par- ticular case, but by the establishment of general laws.”—Wuxz- wELL: Bridgewater Treatise. “The only distinct meaning of the word ‘natural’ is stated, Jixed, or settled ; since what is natural as much requires and pre- supposes an intelligent agent to render it so, i. e., to effect it con- tinually or at stated times, as what is supernatural or miraculous does to effect it for once.’—Butizr: Analogy of Revealed Re- ligion. “To conclude, therefore, let no man out of a weak conceit of sobriety, or an ill-applied moderation, think or maintain, that a man can search too far or be too well studied in the book of God’s word, or in the book of God’s works; divinity or philosophy ; but rather let men endeavor an endless progress or proficience in both."—Bacon: Advancement of Learning. DARWIN AND HIS THEORIES FROM A RELIGIOUS POINT OF VIEW. “Surely in such a man lived that true charity which is the very essence of the true spirit of Christ.”—Canon ProTurro, “The moral lesson of his life is perhaps even more valuable than is the grand discovery which he has stamped on the world’s history.”'— The Observer (London). “ Darwin’s writings may be searched in vain for an irreverent or unbelieving word.”— The Church Review. “The doctrine of evolution with which Darwin’s name would always be associated lent itself at least as readily to the old promise of God as to more modern but less complete explanations of the universe.”—Canon Barry. . “The fundamental doctrine of the theist is left precisely as it- was. The belief in the great Creator and Ruler of the Universe is, as we have seen, confessed by the author of these doctrines. The grounds remain untouched of faith in the personal Deity who is in intimate relation with individual souls, who is their guide and helper in life, and who can be trusted in regard to the great hereafter.".— The Church Quarterly Review. “Tt appears impossible to overrate the gain we have won in the stupendous majesty of this (Darwin’s) idea of the Creator and creation.” —Sunday-School Chronicle. “Tt is certain that Mr. Darwin’s books contain a marvelous store of patiently accumulated and most interesting facts. Those facts seem to point in the direction of the belief that the Great Spirit of the Universe has wrought slowly and with infinite pa- tience, through innumerable ages, rather than by,abrupt interven- viii DARWIN FROM A RELIGIOUS POINT OF VIEW. tion and by means of great catastrophes, in the production. of the results, in the animate and inanimate world, which now offer to the student of nature boundless scope for observation and inquiry.” —The Christian World. “Let us see, in the funeral honors paid within these holy pre- cincts to our greatest naturalist, a happy trophy of the reconcilia- tion between faith and science."—The Guardian. “That there is some truth in the theory of evolution, however, most scientists, including those of Christian faith, believe, and Mr. Darwin certainly has done much to make the facts plain; but no scientific principle established by him ever has undermined any truth of the Gospel.”"— The Congregationalist. ‘‘ Christian believers are found among the ranks of evolution- ists without apparent prejudice to their faith. Professor Mivart, the zodlogist; Professor Asa Gray, the botanist; Professor Le Conte and Professor Winchell, the geologists, may be named as among these.— The Presbyterian. “In all his simple and noble life Mr. Darwin was influenced by the profoundly religious conviction that nothing was beneath the earnest study of man which had been worthy of the mighty hand of God.”—Canon Farrar. ; “He has not one word to say against religion; ... by-and-by it may be seen that he has done much to put religions faith as well as scientific knowledge on a higher plane.” —Jndependent. “A celebrated author and divine has written to me that ‘he has gradually learned to see that it is just as noble a conception of the Deity to believe that he created a few original forms capable of self-development into other and needful forms, as to believe that he required a fresh act of creation to supply the voids caused by the action of his laws.’”"— Origin of Species, page 422. “Tam at the head of a college where to declare against it [evolution] would perplex my best students, They would ask me which to give up, science or the Bible. . . . It is but the evolu- tion of Genesis when each ‘brings forth after its kind.’ Science tells the same story. But what is the limit of the fixedness of the law? I believe that the evolution of new species is a question in science, and not of religion. It should be left to scientific men.” —President McCosa. CONTENTS. L Tar Movements anp Hastts or Priants. The Movement of Plants in Relation to their Wants. The Power of Movement in Animal and Plant compared. ° Advantages of Cross-Fertilization . - : 5 . Potency of the Sexual Elements in Plants - ‘ ‘ Experiments in Crossing f . ' The Struggle for Existence among Seeds ‘ 6 “Practical Application of these Views . : ‘ Marriages of First Cousins ‘ : Development of the Two Sexes in Plants - ‘ Why the Sexes have been reseparated . 4 . Comparative Fertility of Male and Female Plants Effect of Climate on Reproduction Causes of Sterility among Plants An “Ideal Type” or Inevitable Modification Special Adaptations to a Changing Purpose . An Illustration As interesting on the Theory of Hevelvorne as on dint of Direct TInterposition The Sleep of the Plants Self-Protection during Sleep . Influence of Light upon Plants : Influence of Gravitation upon Plants. : , Ps The Power of Digestion in Plants Diverse Means by which Plants gain their Subsistence How a Plant preys upon Animals PAGE x CONTENTS. Tl. PAGE Tus Part rLayep By Worms IN THE History oF THIS PLANET. They preserve Valuable Ruins : , , . 42 They prepare the Ground for Seed ; : * 43 Intelligence of Worms ‘ , ‘ , - 465 WI. Tur Laws OF VARIABILITY WITH RESPECT TO ANIMALS AND PLANTS. Inherited Effect of Changed Habits : é F : 48 Effects of the Use and Disuse of Parts 2 3 . 50 Vague Origin of our Domestic Animals . ‘ & ‘ 52 Descent of the Domestic Pigeon . : : ‘ . 58 Origin of the Dog. . : . . é ‘ 55 Origin of the Horse . . : : . 57 Causes of Modifications in the Hon, ‘ 5 4 : 58 “ Making the Works of God a mere Mockery ” . . 59 Variability of Cultivated Plants . Z z a . 61 Savage Wisdom in the Cultivation of Plants . < ‘ . 62 Unknown Laws of Inheritance . . : . 64 Laws of Inheritance that are fairly well extablshed : : - 66 Inherited Peculiarities in Man. : i ‘ : 67 Inherited Diseases. 7 : ‘ ‘ : - 68 Causes of Non-Inheritance ‘ : 3 69 Steps by which Domestic Races have — sitdiieadl z e . 71 Unconscious Selection . 5 ‘ i‘ é 13 Adaptation of Animals to the Fancics of Man F P - 4 Doubtful Species . : 3 é 3 ‘ “ 15 Species an Arbitrary Term. a a . 77 The True Plan of Creation : . 49 , IV. THE STRUGGLE For EXISTENCE. Death inevitable in the Fight for Life . . 82 “Inexplicable on the Theory of Creation” s . ® 84 Obscure Checks to Increase . : é : F - 85 Climate as a Check to Increase . a 7 ’ 86 Influence of Insects in the Struggle for Hvistanice, : 2 . 88 No such Thing as Chane i in the Result of the Struggle . F 90 LL Yones CONTENTS. x1 Vv. PAGE Natura SELECTION; oR, THE SURVIVAL OF THE Firvest. An Invented Hypothesis é . 93 How far the Theory may be eatendled - . F . 94 Is there any Limit to what Selection can effect? . ‘ - 96 Has Organization advanced ? . - 2 : j 97 A Higher Workmanship than Man’s . - 99 Why Habits and Structure are not in Agreement 102 No Modification in one Species designed for the Good of denotes » 103 Illustrations of the Action of Natural Selection . - : 106 Divergence of Character - . ; : . - 108 Evolution of the Human Eye 3 3 fj ‘ p 110 VI. GrocrarHicaL Distrisution or Orcanic Brines, Isolated Continents never were united . 115 Means of Dispersal 3 116 These Means of Transport not aoetdentat . 118 Dispersal during the Glacial Period . F : 119 The Theory of Creation inadequate . F . 122 Causes of a Glacial Climate " 123 Difficulties not yet removed . 124 Identity of the Species of Islands witli ffi of the Mainland ex- plained only by this Theory . - 7 . . 125 VII. Evipence or tae Descent or Man From some Lower Forat. Points of Correspondence between Man and the other Animals . 129 The facts of Embryology and the Theory of Development 6-181 Two Principles that explain the Facts 3 7 ° . 184 Embryology against Abrupt Changes 185 Rudimentary Organs only to be explained on the Theory of De. velopment 4 . : - 3 . 187 “No other Explanation has ever been given” . : . 139 Unity of Type explained by Relationship . 140 Inexplicable on the Ordinary View of Creation 3 ‘3 142 Descent with Modification the only Explanation . P . 148 xii CONTENTS. PAGE The History of Life on the Theory of Descent with Modification . 144 Letters retained in the Spelling but Useless in Pronunciation . 146 Man’s Deficiency in Tail . F : ; 147 Points of Resemblance between Man auth Monkey . . . 149 Variability of Man . os Z . a 152 Causes of Variability in Hatislieated Man - és . 158 Action of Changed Conditions . 155 The Inherited Effects of the Increased aud Diminished Use of Parts 156 Reversion as a Factor in the Development of Man é - 158 Reversion in the Human Family . * P - 160 Prepotence in the Transmission of Character . . 162 ~ Natural Selection in the Development of Man 5 5 - 163 How Man became upright : - ‘ F 165 The Brain enlarges as the Mental Faculties ddexelop . i . 167 Nakedness of the Skin. - a 6 169 Is Man the most helpless of the Animals? ‘ : a . 171 Vill. MentaL Powers or Man anp THE LOWER ANIMALS COMPARBD. Fundamental Intuitions the same in Man and the other Animals. 175 Man and the Lower Animals excited by the same Emotions . ~ 1i7 All Animals possess some Power of Reasoning . : 2 79 The Power of Association in Dog and Savage ; , . 181 The Lower Animals progress in Intelligence - 7 ‘ 182 The Power of Abstraction . : c : . . 183 The Evolution of Language : . : 185 Development of Languages and Species enmupaied : . - 188 The Sense of Beauty F ‘ ‘ é . 191 Development of the Ear for Music . . ‘ 5 . 192 IX. DEVELOPMENT OF THE Monat SENSE. From the Social Instincts to the Moral Sense. : ‘i 195 Human Sympathy among Animals. . é : . 197 The Love of Approbation . 2 F c : 5 199 Fellow-Feeling for our Fellow-Animals 2 ‘ ; . 200 Development of the Golden Rule . ‘ ‘ ‘io . a 201 CONTENTS. xiii PAGE Regret peculiar to Man, and why .. ‘ ‘ “ . 202 Remorse explained ‘ : : : < 204 Development of Self-Control . : F A - » 205 Variability of Conscience . . ; ‘ $ 207 Progress not an Invariable Rule é : . 209 All Civilized Nations are the Descendants of oe : 210 “The Ennobling Belief in God” i H 7 . 213 x. Tue GENEALOGY oF Man. Man a Sub-Order . : 7 a : ‘ 218 The Birthplace of Man : F fs é ‘i . 221 Origin of the Vertebrata . ‘i : ‘ 5 224 From no Bone to Backbone . ‘i : F - 226 Does Mankind consist of Several Species ? ? : . : 228 The Races graduate into each other . . - ‘ . 229 Was the First Man a Speaking Animal? . ‘ i. . 231 The Theory of a Single Pair . é s ; , . 281 Civilized out of Existence . E < é 5 . 233 XI. Sexuat SELECTION aS aN AGENCY TO ACCOUNT FoR THE DIFFERENCES BETWEEN THE Races or Man. Struggle of the Males for the Possession of the Females. ., 236 Courtship among the Lower Animals i @ ‘“ 237 Why the Male plays the more Active Part in Courétas . « 239 Transmission of Sexual Characteristics . F ‘ 5 240 An Objection answered c tg ‘ . 242 Difference between the Sexes created by caer Selection ‘ 243 Tow Woman could be made to reach the Standard of Man « 246 “Characteristic Selfishness of Man” é i : 247 No Universal Standard of Beauty among Maukind ‘ ‘ . 248 Development of the Beard : é 3 249 Development of the Marriage-Tic . : ‘i . . 250 Unnatural Selection in Marriage . , a . ‘ 262 Modifying Influences in Both Sexes . : . ‘ ~ 254 “Grounds that will never be shaken” . Fy F ‘ 256 xiv CONTENTS. XII. PAGE Tur Expression or tHE Emorions IN Man AND OTHER ANIMALS. The Principle of Associated Habit . : 5 . . 258 The Principle of Antithesis ‘ F ‘i ‘ : 261 Origin of the Principle of Antithesis . . 263 The Principle of the Action of the Excited Nervous ftom on the Body . . . - ¥ 7 5 F 265 XIII. Means oF THE ExrrEssIoN oF THE EMorIons. Vocal Organs . 7 : é ‘ s ‘ . 268 Erection of the Hair ‘ ‘ . ‘ : 269 Erection of the Ears . 2 : : . . 240 A Startled Horse . é . p : e ‘ 271 Monkey-Shines ‘ - . ‘ ‘ ! . 271 Weeping of Man and Brute < A ‘ e : 272 The Grief-Muscles . 7 c 3 : . 275 Voluntary Power over the Grief- Muscles . < 3 . 276 “Down in the Mouth ” : 3 ‘ 3 : . 278 Laughter . . - ; c 5 279 Expression of the Devout Ruoitons : ; , . . 282 Frowning . . = . . : ‘ : 284 Pouting ‘ _ : é . : . 285 Decision at the Mouth : 3 . ‘i : 5 287 Anger. 7 ‘ 3 : F ‘ é - 287 Sneering . é ‘ . 5 2 é é 288 Disgust : . : 2 ‘ a . 289 Shrugging the Siedliece , . F . . . 290 Blushing . : : . 291 Blushing not aaeiaeacily an iii of Guilt . ‘ si 293 Blushing accounted for ‘ : . - 294 A New Argument for a Single Pivent: Siok P . y 296 XIV. Tue Provisions, Hyporuesis oF PANGENEsIs. Functional Independence of the Units of the Body . ‘ . 299 Necessary Assumptions . : 7 < 7 . 802 “1 CONTENTS, Two Objections answered < : a Effect of Morbid Action . F ‘ i : Transmission limited . XV. ObsEcTIONS TO THE THEORY or DEsceNnT wiTtH MODIFICATION CONSIDERED. Misrepresentations corrected Lapse of Time and Extent of Area Why the Higher Forms have not supplanted his Lower . The Amount of Life must have a Limit The Broken Branches of the Tree of Life Why we do not find Transitional Forms How could the Transitional Form have subsisted ? Why Nature takes no Sudden Leaps . Imperfect Contrivances of Nature accounted for . Instincts as a Difficulty Some Instincts acquired and some joat Tnnumerable Links necessarily lost . Plenty of Time for the Necessary Gradations Wide Intervals of Time between the Geological Voiditioas; Sudden Appearance of Groups of Allicd Species . 3 How little we know of Former Inhabitants of the World The Extinction of Species involved in Mystery Dead Links between Living Species . Living Descendants of Fossil Species Unnecessary to explain the Cause of each individual Ditecence * Face to Face with an Insoluble Difficulty ” Why distasteful? . : “ Accords better with what we sinew of the Creator’s Bawa a The Grandeur of this View of Life Not incompatible with the Belief in Immortality . 310 . dll 313 . 316 817 . 319 322 . 828 324 . 825 327 . 829 331 . 334 336 . 8387 338 . 840 342 . 848 844 . 846 347 - 848 349 DARWINISM STATED BY DARWIN HIMSELF. I. THE MOVEMENTS AND HABITS OF PLANTS. The Power THE most widely_prevalent movement is a ional essentially of the same nature as that of the page 1. stem of a climbing plant, which bends suc- cessively to all points of the compass, so that the tip revolves. This movement has been called by Sachs ‘‘re- volving nutation”; but we have found it much more convenient to use the terms circumnutation and cir- cumnutate. As we shall have to say much about this movement, it will be useful here briefly to describe its nature. If we observe a circumnutating stem, which happens at the time to be bent, we will say toward. the north, it will be found gradually to bend more and more easterly, until it faces the east; and so onward to the south, then to the west, and back again to the north. If the movement had been quite regular, the apex would have described a circle, or rather, as the stem is always growing upward, a circular spiral. But it generally de- scribes irregular elliptical or oval figures; for the apex, after pointing in any one direction, commonly moves back to the opposite side, not, however, returning along 2 DARWINISM STATED BY DARWIN HIMSELF. the same line. Afterward other irregular ellipses or ovals are successively described, with their longer axes directed to different points of the compass. While describing such figures, the apex often travels in a zigzag line, or _makes small subordinate loops or triangles. In the case of leaves the ellipses are generally narrow. Even the stems of seedlings before they have broken through the ground, as well as their buried radicles, cireumnutate, as far as the pressure of the surrounding earth permits. In this universally present movement we have the basis or groundwork for the acquirement, according to the requirements of the plant, of the most diversified movements. Page 3. THE MOVEMENT OF PLANTS IN RELATION TO THEIR WANTS. The Move- . . BS erty Bud The most interesting point in the natural Habits of history of climbing plants is the various kinds pearing of movement which they display in manifest page 202. relation to their wants. The most different organs—stems, branches, flower-peduncles, petioles, mid- ribs of the leaf and leaflets, and apparently aérial roots— all possess this power. 1. The first action of a tendril is to place itself in a proper position. For instance, the tendril of Cobq@a first rises vertically up, with its branches divergent and with the terminal hooks turned outward ; the young shoot at the extremity of the stem is at the same time bent to one side, so as to be out of the way. The young leaves of clematis, on the other hand, prepare for action by tem- porarily curving themselves downward, so as to serve as grapnels. 2. If a twining plant or a tendril gets by any accident into an inclined position, it soon bends upward, though THE MOVEMENTS AND HABITS OF PLANTS. . 3 secluded from the light. The guiding stimulus no doubt is the attraction of gravity, as Andrew Knight’ showed to be the case with germinating plants. Ifa shoot of any ordinary plant be placed in an inclined position in a glass of water in the dark, the extremity will, in a few hours, bend upward ; and, if the position of the shoot be then reversed, the downward-bent shoot reverses its curvature ; but if the stolon of a strawberry, which has no tendency to grow upward, be thus treated, it will curve downward in the direction of, instead of in opposition to, the force of gravity. As with the strawberry, so it is generally with the twining shoots of the Hibbertia dentata, which climbs laterally from bush to bush ; for these shoots, if placed in a position inclined downward, show little and some- times no tendency to curve upward. 3. Climbing plants, like other plants, bend toward the light by a movement closely analogous to the incurv- ation which causes them to revolve, so that their revoly- ing movement is often accelerated or retarded in travel- ing to or from the light. On the other hand, in a few instances tendrils bend toward the dark. 4. We have the spontaneous revolving movement which is independent of any outward stimulus, but is contingent on the youth of the part, and on vigorous health ; and this again, of course, depends on a proper temperature and other favorable conditions of life. 5. Tendrils, whatever their homological nature may be, and the petioles or tips of the leaves of leaf-climbers, and apparently certain roots, all have the power of move- ment when touched, and bend quickly toward the touched side. Extremely slight pressure often suffices. If the pressure be not permanent, the part in question straight- ens itself and is again ready to bend on being touched. 6. Tendrils, soon after clasping a support, but not 4 DARWINISM STATED BY DARWIN HIMSELF. after a mere temporary curvature, contract spirally. If they have not come into contact with any object, they ultimately contract spirally, after ceasing to revolve ; but in this case the movement is useless, and occurs only after a, considerable lapse of time. With respect to the means by which these various movements are effected, there can be little doubt, from the researches of Sachs and H. de Vries, that they are due to unequal growth ; but, from the reasons already assigned, I can not believe that this explanation applies to the rapid movements from a delicate touch. Finally, climbing plants are sufficiently numerous to form a conspicuous feature in the vegetable kingdom, more especially in tropical forests. America, which so abounds with arboreal animals, as Mr. Bates remarks, likewise abounds, according to Mohl and Palm, with climbing plants ; and, of the tendril-bearing plants exam- ined by me, the highest developed kinds are natives of this grand continent, namely, the several species of Big- nonia, Eccremocarpus, Cobea, and Ampelopsis. But even in the thickets of our temperate regions the number of climbing species and individuals is considerable, as will be found by counting them. THE POWER OF MOVEMENT IN ANIMAL AND PLANT COMPARED. It has often been vaguely asserted that plants are distinguished from animals by not having the power of movement. It should rather be said that plants acquire and display this power only when it is of some advantage to them ; this being of comparatively rare occurrence, as they are affixed to the ground, and food is brought to them by the air and rain. We see how high in the scale of organization a plant may rise, Page 206. THE MOVEMENTS AND HABITS OF PLANTS. 5 when we look at one of the more perfect tendril-bearers. It first places its tendrils ready for action, as a polypus places its tentacula. If the tendril be displaced, it is acted on by the force of gravity and rights itself. It is acted on by the light, and bends toward or from it, or disregards it, whichever may be most advantageous. Dur- ing several days the tendrils or internodes, or both, spon- taneously revolve with a steady motion. The tendril strikes some object, and quickly curls round and firmly grasps it. In the course of some hours it contracts into a spire, dragging up the stem, and forming an excellent spring. AJl movements now cease. By growth the tis- sues soon become wonderfully strong and durable. The tendril has done its work, and has done it in an admirable manner. The Power It is impossible not to be struck with the = Pits ent resemblance between the foregoing movements page 571. of plants and many of the actions performed unconsciously by the lower animals. With plants an as- tonishingly small stimulus suffices ; and even with allied plants one may be highly sensitive to the slightest con- tinued pressure, and another highly sensitive to a slight momentary touch. The habit of moving at certain pe- riods is inherited both by plants and animals; and several other points of similitude have been specified. But the most striking resemblance is the localization of their sensitiveness, and the transmission of an influence from the excited part to another which consequently moves. Yet plants do not, of course, possess nerves or a central nervous system; and we may infer that with animals such structures serve only for the more perfect transmis- sion of impressions, and for the more complete intercom- munication of the several parts. 6 DARWINISM STATED BY DARWIN HIMSELF. ADVANTAGES OF CROSS-FERTILIZATION. The Effects There are two important conclusions which of ores and may be deduced from my observations: 1. zation inthe That the advantages of cross-fertilization do Lk ely not follow from some mysterious virtue in the page 443. mere union of two distinct individuals, but from such individuals having been subjected during pre- vious generations to different conditions, or to their having varied in a manner commonly called spontaneous, so that in either case their sexual elements have been in some de- gree differentiated ; and, 2. That the injury from self- fertilization follows from the want of such differentiation in the sexual elements. These two propositions are fully established by my experiments. Thus, when plants of the Zpomea and of the Mimulus, which had been self- fertilized for the seven previous generations, and had been kept all the time under the same conditions, were inter- crossed one with another, the offspring did not profit in the least by the cross. The curious cases of plants which can fer- tilize and be fertilized by any other individual of the same species, but are altogether sterile with their own pollen, become intelligible, if the view here pro- pounded is correct, namely, that the individuals of the same species growing in a state of nature near together have not really been subjected during several previous generations to quite the same conditions. Page 451. POTENCY OF THE SEXUAL ELEMENTS IN PLANTS. It is obvious that the exposure of two sets of plants during several generations to differ- ent conditions can lead to no beneficial results, as far as Page 446. THE MOVEMENTS AND HABITS OF PLANTS. v4 crossing is concerned, unless their sexual elements are thus affected. That every organism is acted on to a cer- tain extent by a change in its environment will not, I pre- sume, be disputed. It is hardly necessary to advance evidence on this head ; we can perceive the difference be- tween individual plants of the same species which have grown in somewhat more shady or sunny, dry or damp places. Plants which have been propagated for some gen- erations under different climates or at different seasons of the year transmit different constitutions to their seed- lings. Under such circumstances, the chemical consti- tution of their fluids and the nature of their tissues are often modified. Many other such facts could be adduced. In short, every alteration in the function of a part is probably connected with some corresponding, though often quite imperceptible, change in structure or compo- sition. Whatever affects an organism in any way, likewise tends to act on its sexual elements. We see this in the inheritance of newly acquired modifications, such as those from the increased use or disuse of a part, and even from mutilations if followed by disease. We have abundant evidence how susceptible the reproductive system is to changed conditions, in the many instances of animals ren- dered sterile by confinement; so that they will not unite, or, if they unite, do not produce offspring, though the confinement may be far from close ; and of plants ren- dered sterile by cultivation. But hardly any cases afford more striking evidence how powerfully a change in the conditions of life acts on the sexual elements than those already given, of plants which are completely self-sterile in one country, and, when brought to another, yield, even in the first generation, a fair supply of self-fertilized seeds. 8 DARWINISM STATED ‘BY DARWIN IIMSELF. But it may be said, granting that changed conditions act on the sexual elements, How can two or more plants growing close together, either in their native country or in a garden, be differently acted on, inasmuch as they appear to be exposed to exactly the same conditions ? EXPERIMENTS IN CROSSING. In my experiments with Digitalis pur- purea, some flowers on a wild plant were self- fertilized, and others were crossed with pollen from another plant growing within two or three feet distance. The crossed and self-fertilized plants raised from the seeds thus obtained produced flower-stems in number as 100 to 47, and in average height as 100 to 70. Therefore, the cross between these two plants was highly beneficial ; but how could their sexual elements have been differen- tiated by exposure to different conditions ? If the progeni- tors of the two plants had lived on the same spot during the last score of generations, and had never been crossed with any plant beyond the distance of a few feet,-in all probability their offspring would have been reduced to the same state as some of the plants in my experiments —such as the intercrossed plants of the ninth generation of Ipomeea, or the self-fertilized plants of the eighth gen- eration of Mimulus, or the offspring from flowers on the same plant; and in this case a cross between the two plants of Digitalis would have done no good. But seeds are often widely dispersed by natural means, and one of the above two plants, or one of their ancestors, may have come from a distance, from a more shady or sunny, dry or moist place, or from a different kind of soil containing other organic seeds or inorganic matter. Page 447. THE MOVEMENTS AND HABITS OF PLANTS. 9 THE STRUGGLE FOR EXISTENCE AMONG SEEDS. Seeds often lie dormant for several years in the ground, and germinate when brought near the surface by any means, as by burrowing ani- mals. They would probably be affected by the mere cir- cumstance of having long lain dormant; for gardeners believe that the production of double flowers, and of fruit, is thus influenced. Seeds, moreover, which were matured during different seasons will have been subjected during the whole course of their development to differ- ent degrees of heat and moisture. It has been shown that pollen is often carried by insects to a considerable distance from plant to plant. Therefore, one of the parents or ancestors of our two plants of Digitalis may have been crossed by a dis- tant plant growing under somewhat different condi- tions. Plants thus crossed often produce an unusually large number of seeds; a striking instance of this fact is afforded by the Bignonia, which was fertilized by Fritz Miller with pollen from some adjoining plants and set hardly any seed, but, when fertilized with pollen from a distant plant, was highly fertile. Seedlings from a cross of this kind grow with great vigor, and trans- mit their vigor to their descendants. These, therefore, in the struggle for life, will generally beat and exterminate the seedlings from plants which have long grown near together under the same conditions, and will thus tend to spread. Page 449. PRACTICAL APPLICATION OF THESE VIEWS. Under a practical point of view, agricult- urists and horticulturists may learn something from the conclusions at which we have arrived. Firstly, 2 Page 458, 10 DARWINISM STATED BY DARWIN HIMSELF. we see that the injury from the close breeding of animals and from the self-fertilization of plants does not neces- sarily depend on any tendency to disease or weakness of constitution common to the related parents, and only in- directly on their relationship, in so far as they are apt to resemble each other in all respects, including their sexual nature. And, secondly, that the advantages of cross- fertilization depend on the sexual elements of the parents having become in some degree differentiated by the ex- posure of their progenitors to different conditions, or from their having intercrossed with individuals thus exposed; or, lastly, from what we call in our ignorance spontaneous variation. He therefore who wishes to pair closely related animals ought to keep them under conditions as different as possible. As some kinds of plants suffer much more from self-fertilization than do others, so it probably is with animals from too close interbreeding. The effects of close interbreeding on animals, judging again from plants, would be deterioration in general vigor, including fertility, with no necessary loss of excellence of form ; and this seems to be the usual result. It is a common practice with horticulturists to obtain seeds from another place having a very different soil, so as to avoid raising plants for a long succession of genera- tions under the same conditions; but, with all the species which freely intercross by the aid of insects or the wind, it would be an incomparably better plan to obtain seeds of the required variety, which had been raised for some generations under as different conditions as possible, and sow them in alternate rows with seeds matured in the old garden, The two stocks would then intercross, with a thorough blending of their whole organizations, and with Page 459. THE MOVEMENTS AND HABITS OF PLANTS. 1l no loss of purity to the variety ; and this would yield far more favorable results than a mere exchange of seeds. We have seen in my experiments how wonderfully the offspring profited in height, weight, hardiness, and fer- tility, by crosses of this kind. For instance, plants of Ipomea thus crossed were to the intercrossed plants of the same stock, with which they grew in competition, as 100 to 78 in height, and as 100 to 51 in fertility ; and plants of Hschscholtzia similarly compared were as 100 to 45 in fertility. In comparison with self-fertilized plants the results are still more striking ; thus cabbages derived from a cross with a fresh stock were to the self-fertilized as 100 to 22 in weight. Florists may learn, from the four cases which have been fully described, that they have the power of fixing each fleeting variety of color, if they will fertilize the flowers of the desired kind with their own pollen for half a dozen generations, and grow the seedlings under the same conditions. But a cross with any other in- dividual of the same variety must be carefully prevented, as each has its own peculiar constitution. After a dozen generations of self-fertilization, it is probable that the new variety would remain constant even if grown under somewhat different conditions; and there would no longer be any necessity to guard against intercrosses between the individuals of the same variety. MARRIAGES OF FIRST COUSINS. With respect to mankind, my son George has endeavored to discover by a statistical in- vestigation whether the marriages of first cousins are at all injurious, although this is a degree of relationship which would not be objected to in our domestic animals ; and he has come to the conclusion from his own re- Page 460. 12 DARWINISM STATED BY DARWIN HIMSELF. searches, and those of Dr. Mitchell, that the evidence as to any evil thus caused is conflicting, but on the whole points to its being very small. From the facts given in this volume we may infer that with mankind the mar- riages of nearly related persons, some of whose parents and ancestors had lived under very different conditions, would be much less injurious than that of persons who had always lived in the same place and followed the same habits of life. Nor can I see reason to doubt that the widely different habits of life of men and women in civilized nations, especially among the upper classes, would tend to counterbalance any evil from marriages between healthy and somewhat closely related persons. DEVELOPMENT OF THE TWO SEXES IN PLANTS. Under a theoretical point of view it is some gain to science to know that numberless struct- ures in hermaphrodite plants, and probably in hermaph- rodite animals, are special adaptations for securing an occasional cross between two individuals ; and that the advantages from such a cross depend altogether on the beings which are united, or their progenitors, having had their sexual elements somewhat differentiated, so that the embyro is benefited in the same manner as is a mature plant or animal by a slight change in its condi- tions of life, although in a much higher degree. Another and more important result may be deduced from my observations. Eggs and seeds are highly ser- viceable as a means of dissemination, but we now know that fertile eggs can be produced without the aid of the male. There are also many other methods by which organisms can be propagated asexually. Why then have the two sexes been developed, and why do males exist Page 461. THE MOVEMENTS AND HABITS OF PLANTS. 13 which can not themselves produce offspring ? The an- swer lies, as I can hardly doubt, in the great good which is derived from the fusion of two somewhat differentiated individuals ; and with the exception of the lowest organ- isms this is possible only by means of the sexual elements, these consisting of cells separated from the body, con- taining the germs of every part, and capable of being fused completely together. It has been shown in the present volume that the offspring from the union of two distinct individuals, especially if their progenitors have been subjected to very different conditions, have an immense advantage in height, weight, constitutional vigor and fertility over the self- fertilized offspring from one of the same parents. And this fact is amply sufficient to account for the develop- ment of the sexual elements, that is, for the genesis of the two sexes. It is a different question why the two sexes are some- times combined in the same individual, and are sometimes separated. As with many of the lowest plants and ani- mals the conjugation of two individuals, which are either quite similar or in some degree different is a common phenomenon, it seems probable, as remarked in the last chapter, that the sexes were primordially separate. The individual which receives the contents of the other, may be called the female ; and the other, which is often smaller and more locomotive, may be called the male; though these sexual names ought hardly to be applied as long as the whole contents of the two forms are blended into one. The object gained by the two sexes becoming united in the same hermaphrodite form probably is to allow of occasional or frequent self-fertilization, so as to insure the propagation of the species, more especially in the case of organisms affixed for life to the same spot. 14 DARWINISM STATED BY DARWIN HIMSELF. There does not seem to be any great difficulty in under- standing how an organism, formed by the conjugation of two individuals which represented the two incipient sexes, might have given rise by budding first to a mona- cious and then to an hermaphrodite form ; and in the case of animals even without budding to an hermaphro- dite form, for the bilateral structure of animals perhaps indicates that they were aboriginally formed by the fusion of two individuals. WHY THE SEXES HAVE BEEN RESEPARATED. It is a more difficult problem why some plants, and apparently all the higher animals, after becoming hermaphrodites, have since had their sexes reseparated. This separation has been attributed by some naturalists to the advantages which follow from a division of physiological labor. The principle is intelligible when the same organ has to perform at the same time diverse functions ; but it is not obvious why the male and female glands, when placed in different parts of the same com- pound or simple individual, should not perform their functions equally well as when placed in two distinct in- dividuals. In some instances the sexes may have been reseparated for the sake of preventing too frequent self- fertilization ; but this explanation does not seem prob- able, as the same end might have been gained by other and simpler means, for instance, dichogamy. It may be that the production of the male and female reproductive elements and the maturation of the ovules was a strain and expenditure of vital force for a gs dividual to withstand, if endowed with a highly complex organization ; and that at the same time there was no need for all the individuals to produce young, and conse- Page 463, too great ingle in- THE MOVEMENTS AND HABITS OF PLANTS. 15 quently that no injury, on the contrary, good, resulted from half of them, or the males, failing to produce off- spring. COMPARATIVE FERTILITY OF MALE AND FEMALE PLANTS. The Differ. Thirteen bushes (of the spindle-tree) grow- ent Formsof .- : z Flowers, ing near one another in a hedge consisted of page 290. eight females quite destitute of pollen, and of five hermaphrodites with well-developed anthers. In the autumn the eight females were well covered with fruit, excepting one which bore only a moderate number. Of the five hermaphrodites, one bore a dozen or two fruits, and the remaining four bushes several dozen ; but their number was as nothing compared with those on the female bushes, for a single branch, between two and three feet in length, from one of the latter, yielded more than any one of the hermaphrodite bushes. The difference in the amount of fruit produced by the two sets of bushes is all the more striking, as from the sketches above given it is obvious that the stigmas of the polleniferous flowers can hardly fail to receive their own pollen ; while the fertilization of the female flowers de- pends on pollen being brought to them by flies and the smaller Hymenoptera, which are far from being such effi- cient carriers as bees. : I now determined to observe more carefully during successive seasons some bushes growing in another place about a mile distant. As the female bushes were so highly productive, I marked only two of them with the letters A and B, and five polleniferous bushes with the letters C to G. I may premise that the year 1865 was highly favorable for the fruiting of all the bushes, espe- cially for the polleniferous ones, some of which were 16 DARWINISM STATED BY DARWIN HIMSELF. quite barren, except under such favorable conditions. The season of 1864 was unfavorable. In 1863 the female A produced ‘‘some fruit”; in 1864 only nine ; and in 1865 ninety-seven fruit. The female B in 1863 was “covered with fruit”; in 1864 it bore twenty-eight ; and in 1865 ‘innumerable very fine fruits.” I may add that three other female trees growing close by were ob- served, but only during 1863, and they then bore abun- dantly. With respect to the polleniferous bushes, the one marked C did not bear a single fruit during the years 1863 and 1864, but during 1865 it produced no less than ninety-two fruit, which, however, were very poor. I se- lected one of the finest branches with fifteen fruit, and these contained twenty seeds, or on an average 1°33 per fruit. I then took by hazard fifteen fruit from an ad- joining female bush, and these contained forty-three seeds ; that is, more than twice as many, or on an aver- age 2°86 per fruit. Many of the fruits from the female bushes included four seeds, and only one had a single seed ; whereas, not one fruit from the polleniferous bushes contained four seeds. Moreover, when the two lots of seeds were compared, it was manifest that those from the female bushes were the larger. The second polleniferous bush, D, bore in 1863 about two dozen fruit, in 1864 only three very poor fruit, each containing a single seed; and in 1865, twenty equally poor fruit. Lastly, the three polleniferous bushes, E, F, and G, did not produce a single fruit during the three years 1863, 1864, and 1865. EFFECT OF CLIMATE ON REPRODUCTION. Page 293, . A tendency to the separation of the sexes in the cultivated strawberry seems to be much more strongly marked in the United States than in Eu- THE MOVEMENTS AND HABITS OF PLANTS. 17 rope ; and this appears to be the result of the direct action of climate on the reproductive organs. In the best ac- count which I have seen, it is stated that many of the varieties in the United States consist of three forms, namely, females, which produce a heavy crop of fruit; of hermaphrodites, which ‘‘seldom produce other than avery scanty crop of inferior and imperfect berries” ; and of males, which produce none. The most skillful cul- tivators plant ‘‘seven rows of female plants, then one row of hermaphrodites, and so on throughout the field.” The males bear large, the hermaphrodites mid-sized, and the females small flowers. The latter plants produce few runners, while the two other forms produce many ; con- sequently, as has been observed both in England and in the United States, the polleniferous forms increase rapidly and tend to supplant the females. We may therefore infer that much more vital force is expended in the pro- duction of ovules and fruit than in the production of pollen. CAUSES OF STERILITY AMONG PLANTS, The _Differ- If the sexual elements belonging to the ent Forms of : ae a ait Flower, same form are united, the union is an illegiti- page 345. mate one, and more or less sterile. With di- morphic species two illegitimate unions, and with trimor- phic species twelve are possible. There is reason to be- lieve that the sterility of these unions has not been spe- cially acquired, but follows as an incidental result from the sexual elements of the two or three forms having been adapted to act on one another in a particular manner, so that any other kind of union is inefficient, like that between distinct species. Another and still more remark- able incidental result is that the seedlings from an ille- gitimate union are often dwarfed and more or less com- 18 DARWINISM STATED BY DARWIN HIMSELF. pletely barren, like hybrids from the union of two widely distinct species. AN “IDEAL TYPE” OR INEVITABLE MODIFICATION ? Fertilization It is interesting to look at one of the mag- . tae nificent exotic species (orchids), or, indeed, at. page 245. one of our humblest forms, and observe how profoundly it has been modified, as compared with all ordinary flowers—with its great labellum, formed of one petal and two petaloid stamens ; with its singular pollen- masses, hereafter to be referred to; with its column formed of seven cohering organs, of which three alone perform their proper function, namely, one anther and two generally confluent stigmas; with the third stigma modified into the rostellum and incapable of being fer- tilized ; and with three of the anthers no longer function- ally active, but serving either to protect the pollen of the fertile anther or to strengthen the column, or existing as mere rudiments, or entirely suppressed. What an amount of modification, cohesion, abortion, and change of function do we here see! Yet hidden in that column, with its surrounding petals and sepals, we know that there are fifteen groups of vessels, arranged three within three, in alternate order, which probably have been pre- served to the present time from being developed at a very early period of growth, before the shape or existence of any part of the flower is of importance for the well-being of the plant. Can we feel satisfied by saying that each orchid was created, exactly as we now see it, on a certain “ideal type”; that the omnipotent Creator, having fixed on one plan for the whole order, did not depart from this plan ; that he, therefore, made the same organ to perform di- THE MOVEMENTS AND HABITS OF PLANTS, 19 verse functions—often of trifling importance compared with their proper function—converted other organs into mere purposeless rudiments, and arranged all as if they had to stand separate, and then made them cohere? Is it not a more simple and intelligible view that all the Orchidee owe what they have in common to descent’ from some monocotyledonous plant, which, like so many other plants of the same class, possessed fifteen organs, arranged alternately, three within three, in five whorls; and that the now wonderfully changed structure of the flower is due to a long course of slow modification—each modification having been preserved which was useful to the plant, during the incessant changes to which the or- ganic and inorganic world has been exposed ? SPECIAL ADAPTATIONS TO A CHANGING PURPOSE. Fertilization It has, I think, been shown that the Or- of Orchids, ¢hidew exhibit an almost endless diversity of page 282. beautiful adaptations. When this or that part has been spoken of as adapted for some special purpose, it must not be supposed that it was originally always formed for this sole purpose. The regular course of events seems to be, that a part which originally served for one pur- pose becomes adapted by slow changes for widely differ- ent purposes. To give an instance: in all the Ophree, the long and nearly rigid caudicle manifestly serves for the application of the pollen-grains to the stigma, when the pollinia are transported by insects to another flower ; and the anther opens widely in order that the pollinium should be easily withdrawn ; but, in the Bee ophrys, the caudicle, by a slight increase in length and decrease in its thickness, and by the anther opening a little more widely, becomes specially adapted for the very different purpose 20 DARWINISM STATED BY DARWIN HIMSELF. of self-fertilization, through the combined aid of the weight of the pollen-mass and the vibration of the flower when moved by the wind. Every gradation between these two states is possible—of which we have a partial instance in O. aranifera. Again, the elasticity of the pedicel of the pollinium in some Vandee is adapted to free the pollen-masses from their anther-cases ; but, by a further slight modification, the elasticity of the pedicel becomes specially adapted to shoot out the pollinium with considerable force, so as to strike the body of the visiting insect. The great cavity in the labellum of many Vandew is gnawed by insects, and thus attracts them; but in Mormodes ignea it is greatly reduced in size, and serves in chief part to keep the labellum in its new position on the summit of the column. From the analogy of many plants we may in- fer that a long, spur-like nectary is primarily adapted to secrete and hold a store of nectar ; but in many orchids it has so far lost this function that it contains fluid only in the intercellular spaces. In those orchids in which the nectary contains both free nectar and fluid in the intercellular spaces, we can see how a transition from the one state to the other could be effected, namely, by less and less nectar being secreted from the inner membrane, with more and more retained within the intercellular spaces. Other analogous cases could be given. Although an organ may not have been originally formed for some special purpose, if it now serves for this end, we are justified in saying that it is specially adapted for it. On the same principle, if a man were to make a machine for some special purpose, but were to use old wheels, springs, and pulleys, only slightly altered, the whole machine, with all its parts, might be said to be specially contrived for its present purpose. Thus through- THE MOVEMENTS AND HABITS OF PLANTS. 21 out nature almost every part of each living being has probably served, in a slightly modified condition, for diverse purposes, and has acted in the living machinery of many ancient and distinct specific forms. In my examination of orchids, hardly any fact has struck me so much as the endless diversities of structure —the prodigality of resources—for gaining the very same end, namely, the fertilization of one flower by pollen from another plant. This fact is to a large extent in- telligible on the principle of natural selection. As all the parts of a flower are co-ordinated, if slight variations in any one part were preserved from being beneficial to the plant, then the other parts would generally have to be modified in some corresponding manner. But these latter parts might not vary at all, or they might not vary in a fitting manner, and these other variations, whatever their nature might be, which tended to bring all the parts into more harmonious action with one another, would be preserved by natural selection. AN ILLUSTRATION. To give a simple illustration: in many orchids the ovarium (but sometimes the foot- stalk) becomes for a period twisted, causing the Jabellum to assume the position of a lower petal, so that insects can easily visit the flower ; but from slow changes in the form or position of the petals, or from new sorts of in- sects visiting the flowers, it might be advantageous to the plant that the labellum should resume its normal position on the upper side of the flower, as is actually the case with Malazis paludosa, and some species of Catasetum, etc. This change, it is obvious, might be simply effected by the continued selection of varieties which had their ovaria less and less twisted ; but, if the Page 284. 22 DARWINISM STATED BY DARWIN HIMSELF. plant only afforded varieties with the ovarium more twisted, the same end could be attained by the selection of such variations, until the flower was turned com- pletely round on its axis. This seems to have actually occurred with Malazis paludosa, for the labellum has ac- quired its present upward position by the ovarium being twisted twice as much as is usual. Again, we have seen that in most Vandee there is a plain relation between the depth of the stigmatic chamber and the length of the pedicel, by which the pollen-masses are inserted; now, if the chamber became slightly less deep from any change in the form of the column, or other unknown cause, the mere shortening of the pedicel would be the simplest corresponding change ; but, if the pedicel did not happen to vary in shortness, the slightest tendency to its becoming bowed from elasticity, as in Phalenopsis, or to a backward hygrometric movement, as in one of the Mazillarias, would be preserved, and the tendency would be continually augmented by selection ; thus the pedicel, as far as its action is concerned, would be modified in the same manner as if it had been short- ened. Such processes carried on during many thousand generations in various ways, would create an endless di- versity of co-adapted structures in the several parts of the flower for the same general purpose. This view affords, I believe, the key which partly solves the prob- lem of the vast diversity of structure adapted for closely analogous ends in many large groups of organic beings. AS INTERESTING ON THE THEORY OF DEVELOPMENT AS ON THAT OF DIRECT INTERPOSITION. The more I study nature, the more I be- come impressed, with ever-increasing force, that the contrivances and beautiful adaptations slowly Page 285. THE MOVEMENTS AND HABITS OF PLANTS, 23 acquired through each part occasionally varying in a slight degree but in many ways, with the preservation of those variations which were beneficial to the organism under complex and ever-varying conditions of life, tran- scend in an incomparable manner the contrivances and adaptations which the most fertile imagination of man could invent. The use of each trifling detail of structure is far from a barren search to those who believe in natural selection. When a naturalist casually takes up the study of an or- ganic being, and does not investigate its whole life (im- perfect though that study will ever be), he naturally doubts whether each trifling point can be of any use, or, indeed, whether it be due to any general law. Some naturalists believe that numberless structures have been created for the sake of mere variety and beauty—much as a workman would make different patterns. I, for one, have often and often doubted whether this or that detail of structure in many of the Orchidee and other plants could be of any service; yet, if of no good, these structures could not have been modeled by the natural preservation of useful variations ; such details can only be vaguely accounted for by the direct action of the con- ditions of life, or the mysterious laws of correlated growth. Fertilization This treatise affords me also an opportunity of Orchids, of attempting to show that the study of or- Pee ganic beings may be as interesting to an ob- server who is fully convinced that the structure of each is due to secondary laws as to one who views every trifling detail of structure as the result of the direct interposition of the Creator. ° 24 DARWINISM STATED BY DARWIN HIMSELF. THE SLEEP OF THE PLANTS. The Power The so-called sleep of leaves is so conspicu- of Movement ong a phenomenon that it was observed as early page 280. as the time of Pliny; and since Linnzus pub- lished his famous essay, ‘“‘Somnus Plantarum,” it has been the subject of several memoirs. Many flowers close at night, and these are likewise said to sleep ; but we are not here concerned with their movements, for although effected by the same mechanism as in the case of young leaves, namely, unequal growth on the opposite sides (as first proved by Pfeffer), yet they differ essentially in being excited chiefly by changes of temperature instead of light ; and in being effected, as far as we can judge, for a differ- ent purpose. Hardly any one supposes that there is any real analogy between the sleep of animals and that of plants, whether of leaves or flowers. It seems, therefore, advisable to give a distinct name to the so-called sleep- movements of plants. These have also generally been con- founded, under the term “‘ periodic,” with the slight daily rise and fall of leaves, as described in the fourth chapter ; and this makes it all the more desirable to give some dis- tinct name to sleep-movements. Nyctitropism and nycti- tropic, i. e., night-turning, may be applied both to leaves and flowers, and will be occasionally used by us; but it would be best to confine the term to leaves. Page 281. Leaves, when they go to sleep, move either upward or downward, or, in the case of the leaflets of compound leaves, forward, that is, toward the apex of the leaf, or backward, that is, toward its base; or, again, they may rotate on their own axis without mov- ing either upward or downward. But in almost every case the plane of the blade is so placed as to stand nearly THE MOVEMENTS AND HABITS OF PLANTS. 25 or quite vertically at night. Therefore the apex, or the base, or either lateral edge, may be directed toward the zenith. Moreover, the upper surface of each leaf, and more especially of each leaflet, is often brought into close contact with that of the opposite one ; and this is sometimes effected by singularly complicated movements. This fact suggests that the upper surface requires more protection than the lower one. For instance, the ter- minal leaflet in trifolium, after turning up at night so as to stand vertically, often continues to bend over until the upper surface is directed downward, while the lower sur- face is fully exposed to the sky ; and an arched roof is thus formed over the two lateral leaflets, which have their upper surfaces pressed closely together. Here we have the unusual case of one of the leaflets not standing verti- cally, or almost vertically, at night. Considering that leaves in assuming their nyctitropic positions often move through an angle of 90° ; that the movement is rapid in the evening ; that in some cases it is extraordinarily complicated ; that with certain seed- lings, old enough to bear true leaves, the cotyledons move vertically upward at night, while at the same time the leafiets move vertically downward ; and that in the same genus the leaves or cotyledons of some species move upward, while those of other species move downward— from these and other such facts, it is hardly possible to doubt that plants must derive some great advantage from such remarkable powers of movement. SELF-PROTECTION DURING SLEEP. The fact that the leaves of many plants place themselves at night in widely different positions from what they hold during the day, but with Page 284. 26 DARWINISM STATED BY DARWIN HIMSELF. the one point in common, that their upper surfaces avoid facing the zenith, often with the additional fact that they come into close contact with opposite leaves or leaf- lets, clearly indicates, as it seems to us, that the object gained is the protection of the upper surfaces from being chilled at night by radiation. There is nothing improb- able in the upper surface needing protection more than the lower, as the two differ m function and structure. All gardeners know that plants suffer from radiation. It is this, and not cold winds, which the peasants of South- ern Europe fear for their olives. Seedlings are often pro- tected from radiation by a very thin covering of straw ; and fruit-trees on walls by a few fir-branches, or even by a fishing-net, suspended over them. There is a variety of the gooseberry, the flowers of which, from being pro- duced before the leaves, are not protected by them from radiation, and consequently often fail to yield fruit. An excellent observer has remarked that one variety of the cherry has the petals of its flowers much curled back- ward, and after a severe frost all the stigmas were killed ; while, at the same time, in another variety with incurved petals, the stigmas were not in the least injured. We are far from doubting that an ad- ditional advantage may be thus gained ; and we have observed with several plants, for instance, Des- modium gyrans, that while the blade of the leaf sinks vertically down at night, the petiole rises, so that the blade has to move through a greater angle in order to assume its vertical position than would otherwise have been necessary ; but with the result that all the leaves on the same plant are crowded together, as if for mutual protection. We doubted at first whether radiation would affect in Page 285. THE MOVEMEMTS AND HABITS OF PLANTS. Q7 any important manner objects so thin as are many cotyle- dons and leaves, and more especially affect differently their upper and lower surfaces ; for, although the tem- perature of their upper surfaces would undoubtedly fall when freely exposed to a clear sky, yet we thought that they would so quickly acquire by conduction the temper- ature of the surrounding air, that it could hardly make any sensible difference to them whether they stood hori- zontally, and radiated into the open sky, or vertically, and radiated chiefly in a lateral direction toward neigh- boring plants and other objects. We endeavored, there- fore, to ascertain something on this head, by preventing the leaves: of several plants from going to sleep, and by exposing to a clear sky, when the temperature was be- neath the freezing-point, these as well as the other leaves on the same plants, which had already assumed their nocturnal vertical position. Our experiments show that leaves thus compelled to remain horizontal at night suf- fered much more injury from frost than those which were allowed to assume their normal vertical position. It may, however, be said that conclusions drawn from such ob- servations are not applicable to sleeping plants, the inhab- itants of countries where frosts do not occur. But in every country, and at all seasons, leaves must be exposed to nocturnal chills through radiation, which might be in some degree injurious to them, and which they would es- cape by assuming a vertical position. The Power Any one who had never observed continu- i rae ously a sleeping plant would naturally suppose page 408. that the leaves moved only in the evening when going to sleep, ang in the morning when awaking ; but he would be quite mistaken, for we have found no exception to the rule that leaves which sleep continue to 28 DARWINISM STATED BY DARWIN HIMSELF. move during the whole twenty-four hours ; they move, however, more quickly when going to sleep and when awaking than at other times. INFLUENCE OF LIGHT UPON PLANTS. The Power The extreme sensitiveness of certain seed- evi" lings to light is highly remarkable. The page 565. cotyledons of Phalaris became curved toward a distant lamp, which emitted so little light that a pen- cil held vertically close to the plants did not cast any shadow which the eye could perceive on a white card. These cotyledons, therefore, were affected by a difference in the amount of light on their two sides, which the eye could not distinguish. The degree of their curvature within a given time toward a lateral light did not cor- respond at all strictly with the amount of light which they received ; the light not being at any time in excess. They continued for nearly half an hour to bend toward a lateral light, after it had been extinguished. They bend with remarkable precision toward it, and this depends on the illumination of one whole side, or on the obscuration of the whole opposite side. The difference in the amount of light which plants at any time receive in comparison with what they have shortly before received seems in all cases to be the chief exciting cause of those movements which are influenced by light. Thus seedlings brought out of darkness bend toward a dim lateral light, sooner than others which had previously been exposed to day- light. We have seen several analogous cases with the nyctitropic movements of leaves. A striking instance was observed in the case of the periodic movements of the cotyledons of a cassia: in the morning a pot was placed in an obscure part of a room, and all the cotyle- dons rose up closed ; another pot had stood in the sun- THE MOVEMENTS AND HABITS OF PLANTS. 29 light, and the cotyledons of course remained expanded ; both pots were now placed close together in the middle of the room, and the cotyledons which had been exposed to the sun immediately began to close, while the others opened ; so that the cotyledons in the two pots moved in exactly opposite directions while exposed to the same degree of light. We found that if seedlings, kept in a dark place, were laterally illuminated by a small wax-taper for only two or three minutes at intervals of about three quarters of an hour, they all became bowed to the point where the taper had been held. We felt much surprised at this fact, and, until we had read Wiesner’s observations, we attributed it to the after-effects of the light; but he has shown that the same degree of curvature in a plant may be induced in the course of an hour by several interrupt- ed illuminations lasting altogether for twenty minutes ag by a continuous illumination of sixty minutes. We be- lieve that this case, as well as our own, may be explained by the excitement from light being due not so much to its actual amount, as to the difference in amount from that previously received ; and in our case there were re- peated alternations from complete darkness to light. In this and in several of the above-specified respects, light seems to act on the tissues of plants almost in the same manner as it does on the nervous system of animals. INFLUENCE OF GRAVITATION UPON PLANTS. Gravitation excites plants to bend away from the center of the earth, or toward it, or to place themselves in a transverse position with respect to it. Although it is impossible to modify in any direct manner the attraction of gravity, yet its influence could be moderated indirectly, in the several ways described in Page 567, 30 DARWINISM STATED BY DARWIN HIMSELF, the tenth chapter; and under such circumstances the same kind of evidence as that given in the chapter on heliotropism showed in the plainest manner that apo- geotropic and geotropic, and probably diageotropic move- ments, are all modified forms of circumnutation. Different parts of the same plant and different species are affected by gravitation in widely different degrees and manners. Some plants and organs exhibit hardly a trace of its action. Young seedlings, which, as we know, cir- cumnutate rapidly, are eminently sensitive ; and we have seen the hypocotyl of Beta bending upward through 109° in three hours and eight minutes. The after-effects of apogeotropism last for above half an hour; and horizon- tally-laid hypocotyls are sometimes thus carried tempo- rarily beyond an upright position. The benefits derived from geotropism, apogeotropism, and diageotropism, are generally so manifest that they need not be specified. With the flower-peduncles of Ozalis, epinasty causes them to bend down, so that the ripening pods may be pro- tected by the calyx from the rain. Afterward they are carried upward by apogeotropism in combination with hyponasty, and are thus enabled to scatter their seeds over a wider space. The capsules and flower-heads of some plants are bowed downward through geotropism, and they then bury themselves in the earth for the pro- tection and slow maturation of the seeds. This burying process is much facilitated by the rocking movement due to circumnutation. In the case of the radicles of several, probably of all seedling plants, sensitiveness to gravitation is confined to the tip, which transmits an influence to the adjoining upper part, causing it to bend toward the center of the earth. That there is transmission of this kind was proved in an interesting manner when horizontally extended THE MOVEMENTS AND HABITS OF PLANTS. 81 radicles of the bean were exposed to the attraction of gravity for an hour or an hour and a half, and their tips were then amputated. Within this time no trace of cur- vature was exhibited, and the radicles were now placed pointing vertically downward ; but an influence had al- ready been transmitted from the tip to the adjoining part, for it soon became bent to one side, in the same manner as would have occurred had the radicle remained horizontal and been still acted on by geotropism. Radi- cles. thus treated continued to grow out horizontally for two or three days, until a new tip was reformed ; and this was then acted on by geotropism, and .the radicle became curved perpendicularly downward. THE POWER OF DIGESTION IN PLANTS. Fasssidvers As we have seen that nitrogenous fluids act ous Plants, very differently on the leavesof Drosera from page 85. = non-nitrogenous fluids, and as the leaves re- main clasped for a much longer time over various organic bodies than over inorganic bodies, such as bits of glass, cin- der, wood, etc., it becomes an interesting inquiry whether they can only absorb matter already in solution, or ren- der it soluble ; that is, have the power of digestion. We shall immediately see that they certainly have this power, and that they act on albuminous compounds in exactly the same manner as does the gastric juice of mammals ; the digested matter being afterward absorbed. This fact, which will be clearly proved, is a wonderful one in the physiology of plants. It may be well to premise, for the sake of any reader who knows nothing about the di- gestion of albuminous compounds by animals, that this is effected by means of a ferment, pepsin, together with Page 86. 32 DARWINISM STATED BY DARWIN HIMSELF. weak hydrochloric acid, though almost any acid will serve. Yet neither pepsin nor an acid by itself has any such power. We have seen that when the glands of the disk are excited by the contact of any object, es- pecially of one containing nitrogenous matter, the outer tentacles and often the blade become inflected ; the leaf being thus converted into a temporary cup or stomach. At the same time the discal glands secrete more copiously, and the secretion becomes acid. Moreover, they trans- mit some influence to the glands of the exterior tentacles, causing them to pour forth a more copious secretion, which also becomes acid or more acid than it was before. As this result is an important one, I will give the evidence. The secretion of many glands on thirty leaves, which had not been in any way excited, was tested with litmus-paper ; and the secretion of twenty-two of these leaves did not in the least affect the color, whereas that of eight caused an exceedingly feeble and sometimes doubt- ful tinge of red. Two other old leaves, however, which appeared to have been inflected several times, acted much more decidedly on the paper. Particles of clean glass were then placed on five of the leaves, cubes of albumen on six, and bits of raw meat on three, on none of which was the secretion at this time in the least acid. After an interval of twenty-four hours, when almost all the tentacles on these fourteen leaves had become more or less inflected, I again tested the secretion, selecting glands which had not as yet reached the center or touched any object, and it was now plainly acid. The degree of acidity of the secretion varied somewhat on the glands of the same leaf. On some leaves a few tentacles did not, from some unknown cause, become inflected, as often happens; and in five instances their secretion was found not to be in the least acid ; while the secretion of THE MOVEMENTS AND HABITS OF PLANTS. 383 the adjoining and inflected tentacles on the same leaf was decidedly acid. With leaves excited by particles of glass placed on the central glands, the secretion which collects on the disk beneath them was much more strongly acid than that poured forth from the exterior tentacles, which were as yet only moderately inflected. When bits of al- bumen (and this is naturally alkaline) or bits of meat were placed on the disk, the secretion collected beneath them was likewise strongly acid. As raw meat moistened with water is slightly acid, I compared its action on lit- mus-paper before it was placed on the leaves, and after- ward when bathed in the secretion ; and there could not be the least doubt that the latter was very much more acid. I have indeed tried hundreds of times the state of the secretion on the disks of leaves which were inflected over various objects, and never failed to find it acid. We may, therefore, conclude that the secretion from unex- cited leaves, though extremely viscid, is not acid or only slightly so, but that it becomes acid, or much more strongly so, after the tentacles have begun to bend over any inorganic or organic object; and still more strongly acid after the tentacles have remained for some time closely clasped over any object. I may here remind the reader that the secretion ap- pears to be to a certain extent antiseptic, as it checks the appearance of mold and infusoria, thus preventing for a time the discoloration and decay of such substances as the white of an egg, cheese, etc. It therefore acts like the gastric juice of the higher animals, which is known to arrest putrefaction by destroying the microzymes. Cubes of about one twentieth of an inch (1°27 millimetre) of moderately roasted meat were placed on five leaves, which became in twelve hours 3 Page 98. 84 DARWINISM STATED BY DARWIN HIMSELF. closely inflected. After forty-eight hours I gently opened one leaf, and the meat now consisted of a minute central sphere, partially digested, and surrounded by a thick en- velope of transparent viscid fluid. The whole, without being much disturbed, was removed and placed under the microscope. In the central part the transverse strie on the muscular fibers were quite distinct ; and it was inter- esting to observe how gradually they disappeared, when the same fiber was traced into the surrounding fluid. They disappeared by the strize being replaced by trans- verse lines formed of excessively minute dark points, which toward the exterior could be seen only under a very high power ; and ultimately these points were lost. Finally, the experiments recorded in this chapter show us that there is a remarkable accordance in the power of digestion between the gastric juice of animals, with its pepsin and hydrochloric acid, and the secretion of Drosera with its ferment and acid be- longing to the acetic series. We can, therefore, hardly doubt that the ferment in both cases is closely similar. Page 134. DIVERSE MEANS BY WHICH PLANTS GAIN THEIR SUB- SISTENCE. Insectivor- Ordinary plants of the higher classes pro- a = ea cure the requisite inorganic elements from the soil by means of their roots, and absorb carbonic acid from the atmosphere by means of their leaves and stems. But we have seen in a previous part of this work that there is a class of plants which digest and afterward absorb animal matter, namely, all the Droseracee, Pingut- cula, and, as discovered by Dr. Hooker, Nepenthes, and to this class other species will almost certainly soon be THE MOVEMENTS AND HABITS OF PLANTS. 35 added. These plants can dissolve matter out of certain vegetable substances, such as pollen, seeds, and bits of leaves. No doubt their glands likewise absorb the salts of ammonia brought to them by the rain. It has also been shown that some other plants can absorb ammonia by their glandular hairs; and these will profit by that brought to them by the rain. There is a second class of plants which, as we have just seen, can not digest, but absorb, the products of the decay of the animals which they capture, namely, Utricularia and its close allies ; and, from the excellent observations of Dr. Mellichamp and Dr. Canby, there can scarcely be a doubt that Sar- racenia and Darlingtonia may be added to this class, though the fact can hardly be considered as yet fully _ proved. There isa third class of plants which feed, as is now generally admitted, on the products of the decay of vegetable matter, such as the bird’s-nest orchis (Weot- tia), etc. Lastly, there is the well-known fourth class of parasites (such as the mistletoe), which are nourished by the juices of living plants. Most, however, of the plants belonging to these four classes obtain part of their carbon, like ordinary species, from the atmosphere. Such are the diversified means, as far as at present known, by which higher plants gain their subsistence. HOW A PLANT PREYS UPON ANIMALS. The genus described is Genlisea ornata. Insectivor- The utricle is formed by a slight enlarge- ous Plants, ment of the narrow blade of the leaf. A hol- page 446. low neck, no less than fifteen times as long as the utricle itself, forms a passage from the transverse slit- like orifice into the cavity of the utricle. A. Carlisle have insisted. My father com- municatcd to me some striking instances, in one of which a man died during the early infancy of his son, and my father, who did not see this son until grown up and out of health, declared that it seemed to him as ‘if his old friend had risen from the grave, with all his highly pe- culiar habits and manners. Peculiar manners pass into tricks, and several instances could be given of their in- heritance ; as in the case, often quoted, of the father who generally slept on his back, with his right leg crossed over the left, and whose daughter, while an infant in the cradle, followed exactly the same habit, though an at- tempt was made to cure her. I will give one instance which has fallen under my own observation, and which is curious froh being a trick associated with a peculiar state of mind, namely, pleasurable emotion. A boy had the singular habit, when pleased, of rapidly moving his fin- gers parallel to each other, and, when much excited, of raising both hands, with the fingers still moving, to the sides of his face on a level with the eyes: when this boy was almost an old man, he could still hardly resist this trick when much pleased, but from its absurdity concealed it. He had eight children. Of these, a girl, when pleased, at the age of four and a half years, moved her fingers in exactly the same way, and, what is still odder, when much excited, she raised both her hands, with her fingers still moving, to the sides of her face, in exactly the same manner as her father had done, and sometimes even still continued to do so when alone. I never heard of any one, excepting this one man and his little daugh- 68 DARWINISM STATED BY DARWIN HIMSELF. ter, who had this strange habit; and certainly imitation was in this instance out of the question. INHERITED DISEASES. Animals and Large classes of diseases uusally appear at Plants, vol. certain ages, such as St. Vitus’s dance in youth, | ii, page 54. consumption in early mid-life, gout later, and apoplexy still later ; and these are naturally inherited at the same period. But, even in diseases of this class, in- stances have been recorded, as with St. Vitus’s dance, showing that an unusually early or late tendency to the dis- ease is inheritable. In most cases the appearance of any inherited disease is largely determined by certain critical periods in each person’s life, as well as by unfavorable conditions. There are many other diseases, which are not attached to any particular period, but which certainly tend to appear in the child at about the same age at which the parent was first attacked. An array of high authori- ties, ancient and modern, could be given in support of this proposition. The illustrious Hunter believed in it; and Piorry cautions the physician to look closely to the child at the period when any grave inheritable disease attacked the parent. Dr. Prosper Lucas, after collecting facts from every source, asserts that affections of all kinds, though not related to any particular period of life, tend to reappear in the offspring at whatever period of life they first appeared in the progenitor. a Esquirol gives several striking instances of * insanity coming on at the same age as that of a grandfather, father, and son, who all committed suicide near their fiftieth year. Many other cases could be given, as of a whole family who became insane at the age of Page 55. THE LAWS OF VARIABILITY. 69 forty. Other cerebral affections sometimes follow the same rule—for instance, epilepsy and apoplexy. A woman died of the latter disease when sixty-three years old ; one of her daughters at forty-three, and the other at sixty- seven : the latter had twelve children, who all died from tubercular meningitis. I mention this latter case because it illustrates a frequent occurrence, namely, a change in the precise nature of an inherited disease, though still affecting the same organ. Two brothers, their father, their paternal uncles, seven cousins, and their paternal grandfather, were all simi- larly affected by a skin-disease, called pityriasis versicolor ; ‘* the disease, strictly limited to the males of the family (though transmitted through the females), usually ap- peared at puberty, and disappeared at about the age of forty or forty-five years.” The second case is that of four brothers, who, when about twelve years old, suffered almost every week from severe headaches, which were relieved only by a recumbent position in a dark room. Their father, paternal uncles, paternal grandfather, and grand-uncles all suffered in the same way from headaches, which ceased at the age of fifty-four or fifty-five in all those who lived so long. None of the females of the family were affected. CAUSES OF NON-INHERITANCE. Animals and A large number of cases of non-inheritance Plants, vol. are intelligible on the principle that a strong ay Baeelet tendency to inheritance does exist, but that it is overborne by hostile or unfavorable conditions of life. No one would expect that our improved pigs, if forced during several generations to travel about and root in the x0 DARWINISM STATED BY DARWIN HIMSELF. ground for their own subsistence, would transmit, as truly as they now do, their short muzzles and legs, and their tendency to fatten. Dray-horses assuredly would not long transmit their great size and massive limbs, if com- pelled to live ina cold, damp, mountainous region ; we have, indeed, evidence of such deterioration in the horses which have run wild on the Falkland Islands. European dogs in India often fail to transmit their true character. Our sheep in tropical countries lose their wool in a few generations. There seems also to be a close relation be- tween certain peculiar pastures and the inheritance of an enlarged tail in fat-tailed sheep, which form one of the most ancient breeds in the world. With plants, we have seen that tropical varieties of maize lose their proper character in the course of two or three generations, when cultivated in Europe; and conversely so it is with Euro- pean varieties cultivated in Brazil. Our cabbages, which here come so true by seed, can not form heads in hot countries. According to Carriére, the purple-leafed beech and barberry transmit their character by seed far less truly in certain districts than in others. Under changed circumstances, periodical habits of life soon fail to be transmitted, as the period of maturity in summer and winter wheat, barley, and vetches. So it is with animals: for instance, a person, whose statement I can trust, pro- cured eggs of Aylesbury ducks from that town, where they are kept in houses, and are reared as early as possible for the London market; the ducks bred from these eggs in a distant part of England, hatched their first brood on January 24th, while common ducks, kept in the same yard and treated in the same manner, did not hatch till the end of March ; and this shows that the period of hatch- ing was inherited. But the grandchildren of these Ayles- bury ducks completely lost their habit of early incuba- THE LAWS OF VARIABILITY, 71 tion, and hatched their eggs at the same time with the common ducks of the same place. Many cases of non-inheritance apparently result from the conditions of life continually inducing fresh varia- bility. We have seen that when the seeds of pears, plums, apples, etc., are sown, the seedlings generally inherit some degree of family likeness. Mingled with these seedlings, a few, and sometimes many, worthless, wild-looking plants commonly appear, and their appearance may be attributed to the principle of reversion. But scarcely a single seed- ling will be found perfectly to resemble the parent-form ; and this may be accounted for by constantly recurring variability induced by the conditions of life. STEPS BY WHICH DOMESTIC RACES HAVE BEEN PRODUCED. Origin of Some effect may be attributed to the direct Species, and definite action of the external conditions Page 22 of life, and some to habit ; but he would be a bold man who would account by such agencies for the differences between a dray and race horse, a greyhound and blood-hound, a carrier and tumbler pigeon. One of the most remarkable features in our domesticated races is that we see in them adaptation, not, indeed, to the ani- mal’s or plant’s own good, but to man’s use or fancy. Some variations useful to him have probably arisen sud- denly, or by one step; many botanists, for instance, be- lieve that the fuller’s teasel, with its hooks, which can not be rivaled by any mechanical contrivance, is only a variety of the wild Dipsacus ; and this amount of change may have suddenly arisen in a seedling. So it has probably been with the turnspit-dog ; and this is known to have been the case with theancon sheep. But when we compare the dray-horse and race-horse, the dromedary and camel, 72 DARWINISM STATED BY DARWIN HIMSELF. the various breeds of sheep fitted either for cultivated land or mountain-pasture, with the wool of one breed good for one purpose, and that of another breed for an- other purpose ; when we compare the many breeds of dogs, each good for man in different ways ; when we com- pare the game-cock, so pertinacious in battle, with other breeds so little quarrelsome, with ‘‘ everlasting layers” which never desire to sit, and with the bantam, so small and elegant ; when we compare the host of agricultural, culinary, orchard, and flower-garden races of plants, most useful to man at different seasons and for different pur- poses, or so beautiful in his eyes—we must, I think, look further than to mere variability. We can not suppose that all the breeds were suddenly produced as perfect and as useful as we now see them; indeed, in many cases, we know that this has not been their history. The key is man’s power of accumulative selection: Nature gives successive variations ; man adds them up in certain direc- tions useful to him. In this sense he may be said to have made for himself useful breeds. If selection consisted merely in separating some very distinct variety, and breeding from it, the principle would be so obvious as hardly to be worth notice ; but its importance consists in the great effect produced by the accumulation in one direction, during successive generations, of differences absolutely inappre- ciable by an uneducated eye—differences which I for one have vainly attempted to appreciate. Not one man ina thousand has accuracy of eye and judgment sufficient to become an eminent breeder. If gifted with these quali- ties, and he studies his subject for years, and devotes his lifetime to it with indomitable perseverance, he will suc- ceed, and may make great improvements; if he wants Page 28. THE LAWS OF VARIABILITY. 3 any of these qualities, he will assuredly fail. Few would readily believe in the natural capacity and years of prac- tice requisite to become even a skillful pigeon-fancier. UNCONSCIOUS SELECTION. Origin of A man who intends keeping pointers nat- Species, urally tries to get as good dogs as he can, and page 20. afterward breeds from his own best dogs, but he has no wish or expectation of permanently altering the breed. Nevertheless, we may infer that this process, con- tinued during centuries, would improve and modify any breed, in the same way as Bakewell, Collins, etc., by this very same process, only carried on more methodically, did greatly modify, even during their lifetimes, the forms and qualities of their cattle. Slow and insensible changes of this kind can never be recognized unless actual meas- urements or careful drawings of the breeds in question have been made long ago, which may serve for compari- son. In some cases, however, unchanged or but little changed individuals of the same breed exist in less civil- ized districts, where the breed has been less improved. There is reason to believe that King Charles’s spaniel has been unconsciously modified to a large extent since the time of that monarch. Some highly competent authori- ties are convinced that the setter is directly derived from the spaniel, and has probably been slowly altered from it. It is known that the English pointer has been greatly changed within the last century, and in this case the change has, it is believed, been chiefly effected by crosses with the fox-hound ; but what concerns us is, that the change has been effected unconsciously and gradually, and yet so effectually, that, though the old Spanish pointer certainly came from Spain, Mr. Borrow has not 74. DARWINISM STATED BY DARWIN HIMSELF. seen, as Iam informed by him, any native dog in Spain like our pointer. By a similar process of selection, and by careful train- ing, English race-horses have come to surpass in fleetness and size the parent Arabs, so that the latter, by the regu- lations for the Goodwood races, are favored in the weights which they carry. Lord Spencer and others have shown how the cattle of England have increased in weight and in early maturity, compared with the stock formerly kept in this country. If there exist savages so barbarous as never to think of the inherited character of the off- spring of their domestic animals, yet any one animal par- ticularly useful to them, for any special purpose, would be carefully preserved during famines and other acci- dents, to which savages are so liable, and such choice animals would thus generally leave more offspring than the inferior ones; so that in this case there would be a kind of unconscious selection going on. We see the value set on animals even by the barbarians of Tierra del Fuego, by their killing and devouring their old women, in times of dearth, as of less value than their dogs. Page 26. ADAPTATION OF ANIMALS TO THE FANCIES OF MAN. On the view here given of the important part which selection by man has played, it be- comes at once obvious how it is that our domestic races show adaptation in their structure or in their habits to man’s wants or fancies. We can, I think, further under- stand the frequently abnormal character of our domestic races, and likewise their differences being so great in ex- ternal characters, and relatively so slight in internal parts Page 28. THE LAWS OF VARIABILITY. ¥ 63) or organs. Man can hardly select, or only with much difficulty, any deviation of structure excepting such as is externally visible; and, indeed, he rarely cares for what is internal. He can never act by selection, except- ing on variations which are first given to him in some slight degree by nature. Noman would ever try to make a fantail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter till he saw a pigeon with a crop of somewhat unusual size ; and the more abnormal or unusual any character was when it first appeared, the more likely it would be to catch his attention. But to use such an expression as trying to make a fantail is, I have no doubt, in most cases, utterly incorrect. The man who first selected a pigeon with a slightly larger tail, never dreamed what the descendants of that pigeon would become through long-continued, partly unconscious and partly methodi- cal, selection. Perhaps the parent-bird of all fantails had only fourteen tail-feathers somewhat expanded, like the present Java fantail, or like individuals of other and distinct breeds, in which as many as seventeen tail-feath- ers have been counted. Perhaps the first pouter-pigeon did not inflate its crop much more than the turbit now does the upper part of its cesophagus—a habit which is disregarded by all fanciers, as it is not one of the points of the breed. DOUBTFUL SPECIES. Origin of The forms which possess in some consider- Boe able degree the character of species, but which page 36. are so closely similar to other forms, or are so closely linked to them by intermediate gradations, that naturalists do not like to rank them as distinct species, are in several respects the most important for us. We %6 DARWINISM STATED BY DARWIN HIMSELF. have every reason to believe that many of these doubtful and closely allied forms have permanently retained their characters for a long time ; for as long, as far as we know, as have good and true species. Practically, when a nat- uralist can unite by means of intermediate links any two forms, he treats the one as a variety of the other; rank- ing the most common, but sometimes the one first de- scribed, as the species, and the other as the variety. But cases of great difficulty, which I will not here enumerate, sometimes arise in deciding whether or not to rank one form as a variety of another, even when they are closely connected by intermediate links ; nor will the commonly- assumed hybrid nature of the intermediate forms always remove thedifficulty. In very many cases, however, one form is ranked as a variety of another, not because the intermediate links have actually been found, but because analogy leads the observer to suppose either that they do now somewhere exist, or may formerly have existed ; and here a wide door for the entry of doubt and conjecture is opened. Hence, in determining whether a form should be ranked as a species or a variety, the opinion of naturalists having sound judgment and wide experience seems the only guide to follow. We must, however, in many cases, decide by a majority of naturalists, for few well-marked and well-known varieties can be named which have not been ranked as species by at least some competent judges. ; That varieties of this doubtful nature are far from uncommon can not be disputed.. Compare the several floras of Great Britain, of France, or of the United States, drawn up by different botanists, and see what a surprising number of forms have been ranked by one botanist as good species, and by another as mere varieties. Mr. H. THE LAWS OF VARIABILITY, "7 C. Watson, to whom I lie under deep obligation for as- sistance of all kinds, has marked for me one hundred and eighty-two British plants, which are generally considered as varieties, but which have all been ranked by botanists as species ; and in making this list he has omitted many trifling varieties, but which nevertheless have been ranked by some botanists as species, and he has entirely omitted - several highly polymorphic genera. Under genera, in- cluding the most polymorphic forms, Mr. Babington gives two hundred and fifty-one species, whereas Mr. Bentham gives only one hundred and twelve—a difference of one hundred and thirty-nine doubtful forms ! SPECIES AN ARBITRARY TERM. Certainly no clear line of demarkation has as yet been drawn between species and sub- species—that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at, the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and in- dividual differences. These differences blend into each other by an insensible series ; and a series impresses the mind with the idea of an actual passage. Hence I look at individual differences, though of small interest to the systematist, as of the highest impor- tance for us, as being the first steps toward such slight varieties as are barely thought worth recording in works on natural history. And I look at varieties which are in any degree more distinct and permanent as steps toward more strongly-marked and permanent varieties ; and at the latter, as leading to sub-species, and then to species. The passage from one stage of difference to another may, in many cases, be the simple result of the nature of the Page 41. 78 DARWINISM STATED BY DARWIN HIMSELF. organism, and of the different physical conditions to which it has long been exposed ; but with respect to the more important and adaptive characters, the passage from one stage of difference to another may be safely attrib- uted to the cumulative action of natural selection, here- after to be explained, and to the effects of the increased use or disuse of parts. A well-marked variety may there- fore be called an incipient species ; but whether this be- lief is justifiable must be judged by the weight of the various facts and considerations to be given throughout this work. It need not be supposed that all varieties or incipient species attain the rank of species. They may become ex- tinct, or they may endure as varieties for very long pe- riods, as has been shown to be the case by Mr. Wollaston with the varieties of certain fossil land-shells in Madeira, and with plants by Gaston de Saporta. If a variety were to flourish so as to exceed in numbers the parent species, it would then rank as the species, and the species as the variety ; or it might come to supplant and exterminate the parent species ; or both might coexist, and both rank as independent species. But we shall hereafter return to this subject. From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of con- venience, to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in compari- son with mere individual differences, is also applied arbi- trarily, for convenience’ sake. THE LAWS OF VARIABILITY. 79 THE TRUE PLAN OF CREATION. Origin of When the views advanced by me in this Species, volume, and by Mr. Wallace, or when analo- page 425. sous views on the origin of species are generally admitted, we can dimly foresee that there will be a consid- erable revolution in natural history. Systematists will be able to pursue their labors as at present ; but they will not be incessantly haunted by the shadowy doubt whether this or that form be a true species. Hereafter we shall be compelled to acknowl- edge that the only distinction between species and well-marked varieties is, that the latter are known, or believed, to be connected at the present day by interme- diate gradations, whereas species were formerly thus con- nected. Hence, without rejecting the consideration of the present existence of intermediate gradations between any two forms, we shall be led to weigh more carefully and to value higher the actual amount of difference between them. It is quite possible that forms now generally acknowledged to be merely varieties may hereafter be thought worthy of specific names ; and in this case scientific and common language will come into accordance. In short, we shall have to treat species in the same manner as those natural- ists treat genera who admit that genera are merely arti- ficial combinations made for convenience. This may not be a cheering prospect; but we shall at least be freed from the vain search for the undiscovered and undiscov- erable essence of the term species. The other and more general departments of natural history will rise greatly in interest. The terms used by naturalists, of affinity, relationship, community of type, paternity, morphology, adaptive characters, rudimentary Page 426, 80 DARWINISM STATED BY DARWIN HIMSELF, and aborted organs, etc., will cease to be metaphorical, and will have a plain signification. When we no longer look at an organic being as a savage looks at a ship, as something wholly beyond his comprehension ; when we regard every production of nature as one which has had a long history; when we contemplate every complex structure and instinct as the summing up of many con- trivances, each useful to the possessor, in the same way as any great mechanical invention is the summing up of the labor, the experience, the reason, and even the blun- ders of numerous workmen; when we thus view each organic being, how far more interesting—I speak from experience—does the study of natural history become ! A grand and almost untrodden field of inquiry will be opened, on the causes and laws of variation, on correla- tion, on the effects of use and disuse, on the direct ac- tion of external conditions, and so forth. The study of domestic productions will rise immensely in value. A new variety raised by man will be a more important and interesting subject for study than one more species added to the infinitude of already recorded species. Our classi- fications will come to be, as far as they can be so made, genealogies, and will then truly give what may be called the plan of creation. IV. THE STRUGGLE FOR EXISTENCE. Origin of A STRUGGLE for existence inevitably fol- oa lows from the high rate at which all organic age 60. beings tend to increase. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year, otherwise, on the principle of geometrical increase, its numbers would quickly become so inordinately great that no country could support the product. Hence, as more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one indi- vidual with another of the same species, or with the in- dividuals of distinct species, or with the physical condi- tions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable king- doms ; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Al- though some species may be now increasing, more or less rapidly, in numbers, all can not do so, for the world would not hold them. There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered with the 5 82 DARWINISM STATED BY DARWIN HIMSELF. progeny of a single pair. Even slow-breeding man has doubled in twenty-five years, and at this rate, in less than a thousand years, there would literally not be standing- room for his progeny. Linneus has calculated that if an annual plant produced only two seeds—and there is no plant so unproductive as this—and their seedlings next year produced two, and so on, then in twenty years there would be a million plants. The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase ; it will be safest to assume that it begins breeding when thirty years old, and goes on breeding till ninety years old, bringing forth six young in the interval, and surviving till one hundred years old ; if this be so, after a period of from seven hundred and forty to seven hundred and fifty years, there would be nearly nineteen million elephants alive, descended from the first pair. DEATH INEVITABLE IN THE FIGHT FOR LIFE. In a state of nature almost every full- grown plant annually produces seed, and among animals there are very few which do not annually pair. Hence we may confidently assert that all plants and ani- mals are tending to increase at a geometrical ratio, that all would rapidly stock every station in which they could anyhow exist, and that this geometrical tendency to in- crease must be checked by destruction at some period of life. Our familiarity with the larger domestic animals tends, I think, to mislead us : we see no great destruction falling on them, but we do not keep in mind that thou- sands are annually slaughtered for food, and that in a state of nature an equal number would have somehow to be disposed of. Page 52. THE STRUGGLE FOR EXISTENCE. 83 The only difference between organisms which annually produce eggs or seeds by the thousand and those which produce extremely few is, that the slow breeders would require a few more years to people, under favorable con- ditions, a whole district, let it be ever so large. The con- dor lays a couple of eggs and the ostrich a score, and yet in the same country the condor may be the more numer- ous of the two ; the Fulmar petrel lays but one egg, yet it is believed to be the most numerous bird in the world. One fly deposits hundreds of eggs, and another, like the Hippobosca, a single one; but this difference does not determine how many individuals of the two species can be supported in a district. A large number of eggs is of some importance to those species which depend on a fluc- tuating amount of food, for it allows them rapidly to in- crease in number. But the real importance of a large number of eggs or seeds is to.make up for much destruc- tion at some period of life ; and this period in the great majority of cases is an early one. If an animal can in any way protect its own eggs or young, a small number may be produced, and yet the average stock be fully kept up; but, if many eggs or young are destroyed, many must be produced, or the species will become extinct. It would suffice to keep up the full number of a tree, which lived on an average for a thousand years, if a single seed were produced once in a thousand years, supposing that this seed were never destroyed, and could be insured to ger- minate in a fitting place. So that, in all cases, the aver- age number of any animal or plant depends only indi- rectly on the number of its eggs or seeds. In looking at Nature, it is most necessary to keep the foregoing considerations always in mind—never to forget that every single organic being may be said to be striving to the utmost to increase in numbers ; that each lives by 84 DARWINISM STATED BY DARWIN HIMSELF. a struggle at some period of its life ; that heavy destruc- tion inevitably falls either on the young or old during each generation or at recurrent intervals. Lighten any check, mitigate the destruction ever so little, and the number of the species will almost instantaneously increase to any amount. ‘SINEXPLICABLE ON THE THEORY OF CREATION.” Origin of As each species tends. by its geometrical Species, rate of reproduction to increase inordinately page 418. in number, and as the modified descendants of each species will be enabled to increase by as much as they become more diversified in habits and structure, so as to be able to seize on many and widely different places in the economy of nature, there will be a constant tend- ency in natural selection tq preserve the most divergent offspring of any one species. Hence, during a long-con- tinued course of modification, the slight differences charac- teristic of varieties of the same species tend to be aug- mented into the greater differences characteristic of the species of the same genus. New and improved vyarie- ties will inevitably supplant and exterminate the older, less improved, and intermediate varieties ; and thus spe- cies are rendered to a large extent defined and distinct objects. Dominant species belonging to the larger groups within each class tend to give birth to new and dominant forms; so that each large group tends to become still larger, and at the same time more divergent in character. But, as all groups can not thus go on increasing in size, for the world would not hold them, the more dominant groups beat the less dominant. This tendency in the large groups to go on increasing in size and diverging in character, together with the inevitable contingency of THE STRUGGLE FOR EXISTENCE. 85 much extinction, explains the arrangement of all the forms of life in groups subordinate to groups, all within a few great classes, which has prevailed throughout all time. This grand fact of the grouping of all organic beings under what is called the Natural System is utterly inexplicable on the theory of creation. OBSCURE CHECKS TO INCREASE. The causes which check the natural tend- Origin of . Species, ency of each species to increase are most ob- page 53. scure. Look at the most vigorous species; by as much as it swarms in numbers, by so much will it tend to increase still further. We know not exactly what the checks are even in a single instance. Nor will this surprise any one who reflects how ignorant we are on this head, even in regard to mankind, although so incompar- ably better known than any other animal. Eggs or very young animals seem generally to suffer most, but this is not invariably the case. With plants there is a vast destruction of seeds, but, from some obser- vations which I have made it appears that the seedlings suffer most from germinating in ground already thickly stocked with other plants. Seedlings, also, are destroyed in vast numbers by various enemies; for instance, on a piece of ground three feet long and two wide, dug and cleared, and where there could be no choking from other plants, I marked all the seedlings of our native weeds as they came up, and out of 357 no less than 295 were de- stroyed, chiefly by slugs and insects. If turf which has long been mown, and the case would be the same with turf closely browsed by quadrupeds, be let to grow, the more vigorous plants gradually kill the less vigorous, 86 DARWINISM STATED BY DARWIN HIMSELF, tHough fully grown plants; thus out of twenty species growing on a little plot of mown turf (three feet by four) nine species perished, from the other species being allowed to grow up freely. The amount of food for each species, of course, gives the extreme limit to which each can increase ; but very frequently it is not the obtaining food, but the serving as prey to other animals, which determines the average number of a species. Thus, there seems to be little doubt that the stock of partridges, grouse,. and hares on any large estate depends chiefly on the destruction of vermin. If not one head of game were shot during the next twenty years in England, and, at the same time, if no vermin were destroyed, there would, in all probability, be less game than at present, although hundreds of thousands of game animals are now annually shot. On the other hand, in some cases, as with the elephant, none are destroyed by beasts of prey ; for even the tiger in India most rarely dares to attack a young elephant protected by its dam. CLIMATE AS A CHECK TO INCREASE. Climate plays an important part in deter- mining the average numbers of a species, and periodical seasons of extreme cold or drought seem to be the most effective of all checks. I estimated (chiefly from the greatly reduced numbers of nests in the spring) that the winter of 185455 destroyed four fifths of the birds in my own grounds; and this is a tremendous destruc- tion, when we remember that ten per cent is an extraordi- narily severe mortality from epidemics with man. The action of climate scems at first sight to be quite inde- pendent of the struggle for existence ; but, in so far as climate chiefly acts in reducing food, it brings on the Page 54. THE STRUGGLE FOR EXISTENCE. 87 most severe struggle between the individuals, whether of the same or of distinct species, which subsist on the same kind of food. Even when climate—for instance, extreme cold—acts directly, it will be the least vigorous individu- als, or those which have got least food through the advanc- ing winter, which will suffer most. When we travel from south to north, or from a damp region to a dry, we in- variably see some species gradually getting rarer and rarer, and finally disappearing ; and, the change of climate be- ing conspicuous, we are tempted to attribute the whole effect to its direct action. But this is a false view: we forget that each species, even where it most abounds, is constantly suffering enormous destruction at some period of its life, from enemies or from competitors for the same place and food ; and, if these enemies or competitors be in the least.degree favored by any slight change of climate, they will increase in numbers ; and, as each area is already fully stocked with inhabitants, the other species must decrease. When we travel southward and see a species decreasing in numbers, we may feel sure that the cause lies quite as much in other species being favored as in this one being hurt. So it is when we travel northward, but in a somewhat lesser degree, for the number of spe- cies of all kinds, and therefore of competitors, decreases northward ; hence, in going northward, or in ascending a mountain, we far oftener meet with stunted forms, due to the directly injurious action of climate, than we do in proceeding southward or in descending a mountain. When we reach the Arctic regions, or snow-capped sum- mits, or absolute deserts, the struggle for life is almost exclusively with the elements. 88 DARWINISM STATED BY DARWIN HIMSELF. INFLUENCE OF INSECTS IN THE STRUGGLE FOR EXIST- ENCE. In several parts of the world insects deter- mine the existence of cattle. Perhaps Paraguay offers the most curious instance of this ; for here neither cattle nor horses nor dogs have ever run wild, though they swarm southward and northward in a feral state; and Azara and Rengger have shown that this is caused by the greater number in Paraguay of a certain fly, which lays its eggs in the navels of these animals when first born. The increase of these flies, numerous as they are, must be ha- bitually checked by some means, probably by other para- sitic insects. Hence, if certain insectivorous birds were to decrease in Paraguay, the parasitic insects would probably increase ; and this would lessen the number of the navel- frequenting flies ; then cattle and horses would become feral, and this would certainly greatly alter (as indeed I have observed in parts of South America) the vegetation : this again would largely affect the insects, and this, as we have just seen in Staffordshire, the insectivorous birds, and so onward in ever-increasing circles of complexity. Not that under nature the relations will ever be as simple as this. Battle within battle must be continually recur- ring with varying success ; and yet in the long run the forces are so nicely balanced that the face of Nature re- mains for long periods of time uniform, though assuredly the merest trifle would give the victory to one organic being over another. Nevertheless, so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being ; and, as we do not see the cause, we invoke cataclysms to deso- late the world, or invent laws on the duration of the forms of life ! Page 56. THE STRUGGLE FOR EXISTENCE. 89 Nearly all our orchidaceous plants abso- lutely require the visits of insects to remove their pollen-masses and thus to fertilize them. I find from experiments that humble-bees are almost indispensa- ble to the fertilization of the heart’s-ease (Viola tricolor), for other bees do not visit this flower. I have also found that the visits of bees are necessary for the fertilization of some kinds of clover: for instance, 20 heads of Dutch clover ( Trifolium repens) yielded 2,290 seeds, but 20 other heads protected from bees produced not one. Again, 100 heads of red clover (7. pratense) produced 2,700 seeds, but the same number of protected heads produced not a single seed. Humble-bees alone visit red clover, as other bees can not reach the nectar. It has been suggested that moths may fertilize the clovers; but I doubt whether they could do so in the case of the red clover, from their weight not being sufficient to depress the wing-petals. Hence we may infer as highly probable that, if the whole genus of humble-bees became extinct or very rare in England, the heart’s-ease and red clover would become very rare, or wholly disappear. The number of humble-bees in any district depends in a great measure on the number of field-mice, which destroy their combs and nests; and Colonel Newman, who has long attended to the habits of humble-bees, believes that ‘“‘more than two thirds of them are thus destroyed all over England.” Now, the number of mice is largely dependent, as every one knows, on the number of cats; and Colonel Newman says, ‘Near villages and small towns I have found the nests of humble-bees more numerous than else- where, which I attribute to the number of cats that destroy the mice.” Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice Page 57. 90 DARWINISM STATED BY DARWIN HIMSELF. and then of bees, the frequency of certain flowers in that district ! NO SUCH THING AS CHANCE IN THE RESULT OF THE STRUGGLE. When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this! Every one has heard that, when an American forest is cut down, a very different vegetation springs up; but it has been observed that ancient Indian ruins in the Southern United States, which must formerly have been cleared of trees, now display the same beautiful diversity and proportion of kinds as in the surrounding virgin forest. What a struggle must have gone on during long centuries between the several kinds of trees, each annually scattering its seeds by the thousand ; what war between insect and in- sect—between insects, snails, and other animals with birds and beasts of prey—all striving to increase, all feeding on each other, or on the trees, their seeds and seedlings, or on the other plants which first clothed the ground and thus checked the growth of the trees! Throw upa hand- ful of feathers, and all fall to the ground according to definite laws ; but how simple is the problem’where each shall fall compared to that of the action and reaction of the innumerable plants and animals which have deter- mined, in the course of centuries, the proportional num- bers and kinds of trees now growing on the old Indian ruins ! Page 58, It is good thus to try in imagination to give to any one species an advantage over another. Probably in no single instance should we know what to Page 61. THE STRUGGLE FOR EXISTENCE. 91 do. This ought to convince us of our ignorance on the mutual relations of all organic beings—a conviction as necessary as it is difficult to acquire. All that we can do is to keep steadily in mind that each organic being is striving to increase in a geometrical ratio; that each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life and to suffer great destruction. When we reflect on this struggle, we may console ourselves with the full be- lief that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigor- ous, the healthy, and the happy survive and multiply. Vv. NATURAL SELECTION: OR, THE SURVIVAL OF THE FITTEST. Variati THE preservation, during the battle for ariation of _. Sha i Animalsand life, of varieties which possess any advantage eres in structure, constitution, or instinct, I have tion, vol. i, called Natural Selection; and Mr. Herbert page 6. Spencer has well expressed the same idéa by the Survival of the Fittest. The term “natural selec- tion” is in some respects a bad one, as it seems to imply conscious choice ; but this will be disregarded after a little familiarity. No one objects to chemists speaking of “elective affinity”; and certainly an acid has no more choice in combining with a base than the conditions of life have in determining whether or not a new form be selected or preserved. The term is so far a good one as it brings into connection the production of domestic races by man’s power of selection and the natural preservation of varieties and species in a state of nature. For brevity sake I sometimes speak of natural selection as an intelli- gent power ; in the same way as astronomers speak of the attraction of gravity as ruling the movements of the planets, or as agriculturists speak of man making domes- tic races by his power of selection. In the one case, as in NATURAL SELECTION, 93 the other, selection does nothing without variability, and this depends in some manner on the action of the sur- rounding circumstances in the organism. I have, also, often personified the word Nature; for I have found it difficult to avoid this ambiguity ; but I mean by nature only the aggregate action and product of many natural laws, and by laws only the ascertained sequence of events. .AN INVENTED HYPOTHESIS. Ragaiaand in scientific investigations it is permitted Plants, vol.i, to invent any hypothesis, and if it explains paged various large and independent classes of facts it rises to the rank of a well-grounded theory. The un- dulations of the ether and even its existence are hypo- thetical, yet every one now admits the undulatory theory of light. The principle of natural selection may be looked at as a mere hypothesis, but rendered in some degree probable by what we positively know of the variability of organic beings in a state of nature—by what we positively know of the struggle for existence, and the consequent almost inevitable preservation of favorable variations— and from the analogical formation of domestic races. Now, this hypothesis may be tested—and this seems to me the only fair and legitimate manner of considering the whole question — by trying whether it explains several large and independent classes of facts ; such as the geo- logical succession of organic beings, their distribution in past and present times, and their mutual affinities and homologies. If the principle of natural selection does explain these and other large bodies of facts, it ought to be received. On the ordinary view of each species hav- ing been independently created, we gain no scientific ex- planation of any one of these facts. We can only say that 94 DARWINISM STATED BY DARWIN HIMSELF. it has so pleased the Creator to command that the past and present inhabitants of the world should appear in a certain order and in certain areas; that he has impressed on them the most extraordinary resemblances, and has classed them in groups subordinate to groups. But by such statements we gain no new knowledge; we do not connect together facts and laws ; we explain nothing. These facts have as yet received no explana- tion on the theory of independent creation ; they can not be grouped together under one point of view, but each has to be considered as an ultimate fact. As the first origin of life on this earth, as well as the continued life of each individual, is at present quite beyond the scope of science, I do not wish to lay much stress on the greater simplicity of the view of a few forms or of only one form having been originally created, instead of in- numerable miraculous creations having been necessary at innumerable periods; though this more simple view accords well with Maupertuis’s philosophical axiom of “least action.” Page 12. HOW FAR THE THEORY MAY BE EXTENDED. In considering how far the theory of natu- ral selection may be extended—that is, in de- termining from how many progenitors the inhabitants of the world have descended—we may conclude that at least all the members of the same class have descended from a single ancestor. A number of organic beings are included in the same class, because they present, independently of their habits of life, the same fundamental type of struct- ure, and because they graduate into each other. More- over, members of the same class can in most cases be shown to be closely alike at an early embryonic age. Page 13. NATURAL SELECTION. 95 These facts can be explained on the belief of their de- scent from a common form; therefore it may be safely admitted that all the members of the same class are descended from one progenitor. But as the members of quite distinct classes have something in common in structure and much in common in constitution, analogy would lead us one step further, and to infer as probable that all living creatures are descended from a single pro- totype. Descent of Thus a large yet undefined extension may Man, partl, safely be given to the direct and indirect re- ee sults of natural selection; but I now admit, after reading the essay by Nageli on plants, and the re- marks by various authors with respect to animals, more especially those recently made by Professor Broca, that in the earlier editions of my “‘ Origin of Species” I perhaps attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the “Origin” so as to confine my remarks to adaptive changes of structure ; but I am convinced, from the light gained during even the last few years, that very many tructures which now appear to us useless will here- after be proved to be useful, and will therefore come within the range of natural selection. Nevertheless, I did not formerly consider sufficiently the existence of structures, which, as far as we can at present judge, are neither beneficial nor injurious ; and this I believe to be one of the greatest oversights as yet detected in my work. I may be permitted to say, as some excuse, that I had two distinct objects in view : firstly, to show that species had not been separately created ; and, secondly, that natu- ral selection had been the chief agent of change, though largely aided by the inherited effects of habit, and slightly 96 DARWINISM STATED BY DARWIN HIMSELF. by the direct action of the surrounding conditions. I was not, however, able to annul the influence of my former belief, then almost universal, that each species had been purposely created; and this led to my tacit assumption that every detail of structure, excepting rudi- ments, was of some special, though unrecognized, service. Any one with this assumption in his mind would natu- rally extend too far the action of natural selection, either during past or present times. Some of those who admit the principle of evolution, but reject natural selection, seem to forget, when criticising my book, that I had the above two objects in view ; hence if I have erred in giving to natural selection great power, which I am very far from admitting, or in having exaggerated its power, which is in itself probable, I have at least, as I hope, done good service in aiding to overthrow the dogma of separate creations. IS THERE ANY LIMIT TO WHAT SELECTION CAN EFFECT? Animals and The foregoing discussion naturally leads to toe Mn the question, What is the limit to the possible amount of variation in any part or quality, and, consequently, is there any limit to what selection can effect ? Will a race-horse ever be reared fleeter than Kelipse ? Can our prize cattle and sheep be still further improved ? Will a gooseberry ever weigh more than that produced by ‘‘ London” in 1852? Will the beet-root in France yield a greater percentage of sugar? Will future varieties of wheat and other grain produce heavier crops than our present varieties? These questions can not be positively answered ; but it is certain that we ought to be cautious in answering them by a negative. In some lines of variation the limit has probably been reached. NATURAL SELECTION. 97 Youatt believes that the reduction of bone in some of our sheep has already been carried so far that it entails great delicacy of constitution. No doubt there is a limit beyond which the organization can not be modified compati- bly with health or life. The extreme degree of flcetness, for instance, of which a terrestrial animal is capable, may have been acquired by our present race-horses ; but, as Mr. Wallace has well remarked, the question that in- terests us “is not whether indefinite and unlimited change in any or all directions is possible, but whether such differences as do occur in nature could have been pro- duced by the accumulation of varieties by selection.” And in the case of our domestic productions, there can be no doubt that many parts of the organization, to which man has attended, have been thus modified to a greater degree than the corresponding parts in the natural species of the same genera or even families. We see this in the form and size of our light and heavy dogs or horses, in the beak and many other characters of our pigeons, in the size and quality of many fruits, in com- parison with the species belonging to the same natural groups. Page 229. HAS ORGANIZATION ADVANCED ? Origin of The problem whether organization on the Species, page whole has advanced is in many ways excess- ae ively intricate. The geological record, at all times imperfect, does not extend far enough back to show with unmistakable clearness that within the known history of the world organization has largely advanced. Even at the present day, looking to members of the same class, naturalists are not unanimous which forms ought 98 DARWINISM STATED BY DARWIN HIMSELF. to be ranked as highest : thus, some look at the selaceans or sharks, from their approach in some important points of structure to reptiles, as the highest fish ; others look at the teleosteans as the highest. The ganoids stand intermediate between the selaceans and teleosteans; the latter at the present day are largely preponderant in number ; but formerly selaceans and ganoids alone ex- isted ; and in this case, according to the standard of highness chosen, so will it be said that fishes have ad- vanced or retrograded in organization. To attempt to compare members of distinct types in the scale of high- ness seems hopeless; who will decide whether a cuttle- fish be higher than a bee—that insect which the great Von Baer believed to be ‘‘in fact more highly organized than a fish, although upon another type”? In the com- plex struggle for life it is quite credible that crustace- ans, not very high in their own class, might beat ceph- alopods, the highest mollusks; and such crustaceans, though not highly developed, would stand very high in the scale of invertebrate animals, if judged by the most decisive of all trials—the law of battle. Besides these inherent difficulties in deciding which forms are the most advanced in organization, we ought not solely to compare the highest members of a class at any two periods—though undoubtedly this is one and perhaps the most important element in striking a balance—but we ought to compare all the members, high and low, at the two periods. At an ancient epoch the highest and lowest molluscoidal ani- mals, namely, cephalopods and brachiopods, swarmed in numbers; at the present time both groups are greatly reduced, while others, intermediate in organization, have largely increased ; consequently some naturalists main- tain that mollusks were formerly more highly developed than at present; but a stronger case can be made out on NATURAL SELECTION. 99 the opposite side, by considering the vast reduction of brachiopods, and the fact that our existing cephalopods, though few in number, are more highly organized than their ancient representatives. We ought also to compare the relative proportional numbers at any two periods of the high and low classes throughout the world; if, for instance, at the present day fifty thousand kinds of ver- tebrate animals exist, and if we knew that at some for- mer period only ten thousand kinds existed, we ought to look at this increase in number in the highest class, which implies a great displacement of lower forms, as a decided advance in the organization of the world. We thus see how hopelessly difficult it is to compare with per- fect fairness, under such extremely complex relations, the standard of organization of the imperfectly-known faunas of successive periods. Origin of There may truly be said to be a constant eel struggle going on between, on the one hand, the tendency to reversion to a less perfect ‘state, as well as an innate tendency to new variations, and, on the other hand, the power of steady selection to keep the breed true. In the long run selection gains the day, and we do not expect to fail so completely as to breed bird as coarse as a common tumbler-pigeon from a good short-faced strain. But, as long as selection is rapidly going on, much variability in the parts undergoing modi- fication may always be expected. A HIGHER WORKMANSHIP THAN MAN'S, As man can produce, and certainly has Origin of 3 : Species, produced, a great result by his methodical and page bts unconscious means of selection, what may not natural selection affect ? Man can act only on external 100 DARWINISM STATED BY DARWIN HIMSELF. . and visible characters: Nature, if I may be allowed to personify the natural preservation or survival of the fit- test, cares nothing for appearances, except in so far as they are useful to any being. She can act on every inter- nal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good: Nature only for that of the being which she tends. Every selected character is fully exercised by her, as is implied by the fact of their selection. Man keeps the natives of many climates in the same country; he seldom exercises each selected character in some peculiar and fitting manner; he feeds a long and a short beaked pigeon on the same food; he does not exercise a long- backed or long-legged quadruped in any peculiar manner ; he exposes sheep with long and short wool to the same climate. He does not allow the most vigorous males to struggle for the females. He does not rigidly destroy all inferior animals, but protects during each varying season, as far as lies in his power, all his productions. He often begins his selection by some half-monstrous form ; or at least. by some modification prominent enough to catch the eye or to be plainly useful to him. Under nature, the slightest differences of structure or constitution may well turn the nicely-balanced scale in the struggle for life, and so be preserved. How fleeting are the wishes and efforts of man! how short his time! and consequently how poor will be his results, compared with those accumulated by Nature during whole geological periods! Can we won- der, then, that Nature’s productions should be far “‘ truer” in character than man’s productions; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship ? NATURAL SELECTION. 101 It may metaphorically be said that natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations: rejecting those that are bad, pre- serving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in rela- tion to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of Time has marked the lapse of ages, and then so imperfect is our view into long-past geological ages that we see only that the forms of life are now different from what they formerly were. Although natural selection can act only through and for the good of each being, yet characters and structures, which we are apt to consider as of very trifling importance, may thus be acted on. When we see leaf-eating insects green and bark-feeders mottled-gray, the Alpine ptarmigan white in winter, the red-grouse the color of heather, we must believe that these tints are of service to these birds and insects in preserving them from danger. Grouse, if not destroyed at some period of their lives, would increase in countless numbers; they are known to suffer largely from birds of prey; and hawks are guided by eye-sight to their prey— so much 50, that on parts of the Continent persons are warned not to keep white pigeons, as being the most liable to destruction. Hence natural selection might be effective in giving the proper color to each kind of grouse, and in keeping that color, when once acquired, true and constant. Nor ought we to think that the occasional destruction of an animal of any particular color would produce little effect : we should remember how essential Page 66. 102 DARWINISM STATED BY DARWIN I[IMSELF, it is in a flock of white sheep to destroy a lamb with the faintest trace of black. WHY HABITS AND STRUCTURE ARE NOT IN AGREEMENT. Origin of He who believes that each being has been Species, created as we now see it must occasionally page 142. have felt surprise when he has met with an animal having habits and structure not in agreement. What can be plainer than that the webbed feet of ducks and geese are formed for swimming ? Yet there are upland geese with webbed feet which rarely go near the water; and no one except Audubon has seen the frigate-bird, which has all its four toes webbed, alight on the surface of the ocean. On the other hand, grebes and coots are eminently aquatic, although their toes are only bordered by membrane. What seems plainer than that the long toes, not furnished with membrane, of the Grallatores, are formed for walking over swamps and floating plants ? —the water-hen and land-rail are members of this order, yet the first is nearly as aquatic as the coot, and the second nearly as terrestrial as the quail or partridge. In such cases, and many others could be given, habits have changed without a corresponding change of structure. The webbed feet of the upland goose may be said to have become almost rudimentary in function, though not in structure. In the frigate-bird, the deeply-scooped mem- brane between the toes shows that structure has begun to change. He who believes in separate and innumerable acts of creation may say that in these cases it has pleased the Creator to cause a being of one type to take the place of one belonging to another type ; but this seems to me only restating the fact in dignified language. He who believes NATURAL: SELECTION. 103 in the struggle for existence and in the principle of natu- ral selection, will acknowledge that every organic being is constantly endeavoring to increase in numbers; and that if any one being varies ever so little, either in habits or structure, and thus gains an advantage over some other inhabitant of the same country, it will seize on the place of that inhabitant, however different that may be from its own place. Hence it will cause him no surprise that there should be geese and frigate-birds with webbed feet, living on the dry land and rarely alighting on the water ; that there should be long-toed corn-crakes, living in meadows instead of in swamps; that there should be woodpeckers where hardly a tree grows ; that there should be diving thrushes and diving Hymenoptera, and petrels with the habits of auks. NO MODIFICATION IN ONE SPECIES DESIGNED FOR THE GOOD OF ANOTHER. Origin of Natural selection can not possibly produce Species, any modification in a species exclusively for page 162. the good of another species ; though through- out nature one species incessantly takes advantage of, and profits by, the structures of others. But natural selection- can and does often produce structures for the direct in- jury of other animals, as we see in the fang of the adder, and in the ovipositor of the ichneumon, by which its eggs are deposited in the living bodies of other insects. If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection. Although many statements may be found in works on natural his- tory to this effect, I can not find even one which seems to 104 DARWINISM STATED BY DARWIN IIMSELF. me of any weight. It is admitted that the rattlesnake has a poison-fang for its own defense, and for the de- struction of its prey; but some authors suppose that at the same time it is furnished with a rattle for its own in- jury, namely, to warn its prey. I would almost as soon believe that the cat curls the end of its tail when prepar- ing to spring, in order to warn the doomed mouse. It is a much more probable view that the rattlesnake uses its rattle, the cobra expands its frill, and the puff-adder swells while hissing so loudly and harshly, in order to alarm the many birds and beasts which are known to attack even the most venomous species. Snakes act on the same principle which makes the hen ruffle her feath- ers and expand her wings when a dog approaches her chickens ; but I have not space here to enlarge on the many ways by which animals endeavor to frighten away their enemies. Natural selection will never produce in a being any structure more injurious than beneficial to that being, for natural selection acts solely by and for the good of each. No organ will be formed, as Paley has remarked, for the purpose of causing pain or for doing an injury to its pos- sessor. Ifa fair balance be struck between the good and evil caused by each part, each will be found on the whole advantageous. After the lapse of time, under changing conditions of life, if any part comes to be injurious, it will be modified ; or, if it be not so, the being will become extinct as myriads have become extinct. Natural selection tends only to make each organic being as perfect as, or slightly more perfect than, the other inhabitants of the same country with which it comes into competition. And we see that this is the standard of perfection attained under nature. The endemic pro- ductions of New Zealand, for instance, are perfect one NATURAL SELECTION. 105 compared with another; but they are now rapidly yield- ing before the advancing legions of plants and animals introduced from Europe. Natural selection will not pro- duce absolute perfection, nor do we always meet, as far as we can judge, with this high standard under nature. The correction for the aberration of light, is said by Mil- ler not to be perfect even in that most perfect organ, the human eye. Natural selection will modify the structure of the young in relation to the parent, and of the parent in relation to the young. In social animals it will adapt the structure of each individual for the benefit of the whole community, if the community profits by the selected change. What natural selection can not do is, to modify the structure of one species, without giving it any advantage, for the good of another species; and, though statements to this effect may be found in works of natural history, I can not find one case which will bear investigation. A structure used only once in an animal’s life, if of high importance to it, might be modified to any extent by natural selection ; for instance, the great jaws possessed by certain insects, used exclusively for opening the cocoon, or the hard tip to the beak of unhatched birds, used for breaking the egg. It has been asserted that, of the best short-beaked tumbler-pigeons, a greater number perish in the egg than are able to get out of it, so that fanciers assist in the act of hatching. Now, if Nature had to make the beak of a full-grown pigeon very short for the bird’s own advantage, the process of modifi- cation would be very slow, and there would be simultane- ously the most rigorous selection of all the young birds within the egg, which had the most powerful and hardest beaks, for all with weak beaks would inevitably perish ; 6 Page 67, 106 DARWINISM STATED BY DARWIN HIMSELF. or, more delicate and more easily broken shells might be selected, the thickness of the shell being known to vary like every other structure. ILLUSTRATIONS OF THE ACTION OF NATURAL SELECTION. In order to make it clear how, as I believe, Origin of : cegen Species, natural selection acts, I must beg permission page 70. to give one or two imaginary illustrations. Let us take the case of a wolf, which preys on various animals, securing some by craft, some by strength, and some by fleetness; and let us suppose that the fleetest prey, a deer for instance, had from any change in the country increased in numbers, or that other prey had de- creased in numbers, during that season of the year when the wolf was hardest pressed for food. Under such cir- cumstances the swiftest and slimmest wolves would have the best chance of surviving, and so be preserved or se- lected—provided always that they retained strength to master their prey at this or some other period of the year, when they were compelled to prey on other animals. I can see no more reason to doubt that this would be the result, than that man should be able to improve the fleet- ness of his greyhounds by careful and methodical selec- tion, or by that kind of unconscious selection which fol- lows from each man trying to keep the best dogs without any thought of modifying the breed. I may add that, according to Mr. Pierce, there are two varieties of the wolf inhabiting the Catskill Mountains in the United States, one with a light greyhound-like form, which pur- sues deer, and the other more bulky, with shorter legs, which more frequently attacks the shepherd’s flocks. NATURAL SELECTION. 107 Certain plants excrete sweet juice, appar- ently for the sake of eliminating something in- jurious from the sap: this is effected, for instance, by glands at the base of the stipules in some Leguminosae, and at the backs of the leaves of the common laurel. This juice, though small in quantity, is greedily sought by insects ; but their visits do not in any way benefit the plant. Now, let us suppose that the juice or nectar was excreted from the inside of the flowers of a certain num- ber of plants of any species. Insects in seeking the nectar would get dusted with pollen, and would often transport it from one flower to another. The flowers of two dis- tinct individuals of the same species would thus get crossed ; and the act of crossing, as can be fully proved, gives rise to vigorous seedlings, which consequently would have the best chance of flourishing and surviving. The plants which produced flowers with the largest glands or nectaries, excreting most nectar, would oftenest be visited by insects, and would oftenest be crossed ; and so in the long run would gain the upper hand and form a local variety. The flowers, also, which had their stamens and pistils placed, in relation to the size and habits of the particular insect which visited them, so as to favor in any degree the transportal of the pollen, would likewise be favored. We might have taken the case of insects visit- ing flowers for the sake of collecting pollen instead of nectar ; and, as pollen is formed for the sole purpose of fertilization, its destruction appears to be a simple loss to the plant; yet if a little pollen were carried, at first occasionally and then habitually, by the pollen-devour- ing insects from flower to flower, and a cross thus effected, although nine tenths of the pollen were de- stroyed, it might still be a great gain to the plant to be thus robbed; and the individuals which produced Page 73. 108 DARWINISM STATED BY DARWIN HIMSELF. more and more pollen, and had larger anthers, would be selected. When our plant, by the above process long continued, had been rendered highly attractive to insects, they would, unintentionally on their part, regularly carry pollen from flower to flower. DIVERGENCE OF CHARACTER. According to my view, varieties are species in the process of formation, or are, as I have called them, incipient species. How, then, does the lesser difference between varieties become augmented into the greater difference between species? That this does habitually happen, we must infer from most of the in- numerable species throughout nature presenting well- marked differences ; whereas varieties, the supposed pro- totypes and parents of future well-marked species, pre- sent slight and ill-defined differences. Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this va- riety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large a degree of difference as that between the species of the same genus. As has always been my practice, I have sought light on this head from our domestic productions. We shall here find something analogous. It will be admitted that the production of races so different as short-horn and Hereford cattle, race and cart horses, the several breeds of pigeons, etc., could never have been effected by the mere chance accumulation of similar variations during many successive generations. In practice, a fancier is, Page 86. NATURAL SELECTION. 109 for instance, struck by a pigeon having a slightly shorter beak; another fancier is struck by a pigeon having a rather longer beak ; and, on the acknowledged principle that ‘“‘fanciers do not and will not admire a medium standard, but like extremes,” they both go on (as has actually occurred with the sub-breeds of the tumbler- pigeon) choosing and breeding from birds with longer and longer beaks, or with shorter and shorter beaks. Again, we may suppose that, at an early period of history, the men of one nation or district required swifter horses, while those of another required stronger and bulkier horses. The early differences would be very slight ; but, in the course of time, from the continued selection of swifter horses in the one case, and of stronger ones in the other, the differences would become greater, and would be noted as forming two sub-breeds. Ultimately, after the lapse of centuries, these sub-breeds would become converted into two well-established and distinct breeds. As the differences became greater, the inferior animals with intermediate characters, being neither very swift nor very strong, would not have been used for breeding, and will thus have tended to disappear. Here, then, we gee in man’s productions the action of what may be called the principle of divergence, causing differences, at first barely appreciable, steadily to increase, and the breeds to diverge in character, both from each other and from their common. parent. But how, it may be asked, can any analogous prin- ciple apply in nature ? I believe it can and does apply most efficiently (though it was a long time before I saw how), from the simple circumstance that the more diver- sified the descendants from any one species become in structure, constitution, and habits, by so much will they be better enabled to seize on many and widely diversified 110 DARWINISM STATED BY DARWIN HIMSELF. places in the polity of nature, and so be enabled to in- crease in numbers. The advantage of diversification of struct- ure in the inhabitants of the same region is, in fact, the same as that of the physiological division of labor in the organs of the same individual body—a sub- ject so well elucidated by Milne-Edwards. No physiolo- gist doubts that a stomach adapted to digest vegetable matter alone, or flesh alone, draws most nutriment from these substances. So in the general economy of any land, the more widely and perfectly the animals and plants are diversified for different habits of life, so will a greater number of individuals be capable of there supporting themselves. A set of animals, with their organization but little diversified, could hardly compete with a set more perfectly diversified in structure. It may be doubted, for instance, whether the Australian marsupials, which are divided into groups differing but little from each other, and feebly representing, as Mr. Waterhouse and others have remarked, our carnivorous, ruminant, and rodent mammals, could successfully compete with these well-developed orders. In the Australian mammals, we see the process of diversification in an early and incom- plete stage of development. Page 89. EVOLUTION OF THE HUMAN EYE. Origin of To suppose that the eye with all its inim- Ses e itable contrivances for adjusting the focus page 143, to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest NATURAL SELECTION, 111 degree. When it was first said that the sun stood still and the world turned round, the common sense of man- kind declared the doctrine false ; but the old saying of Voz populi vox Dei, as every philosopher knows, can not be trusted in science. Within the highest division of the animal kingdom, namely, the Vertebrata, we can start from an eye so simple that it consists, as in the lancelet, of a little sac of transparent skin, furnished with a nerve and lined with pigment, but destitute of any other ap- paratus. In fishes and reptiles, as Owen has remarked, “the range of gradations of dioptric structures is very great.” It is a significant fact that even in man, ac- cording to the high authority of Virchow, the beau- tiful crystalline lens is formed in the embryo by an ac- cumulation of epidermic cells, lying in a sac-like fold of the skin ; and the vitreous body is formed from em- bryonic subcutaneous tissue. To arrive, however, at a just conclusion regarding the formation of the eye, with all its marvelous yet not absolutely perfect characters, it is indispensable that the reason should conquer the im- agination ; but I have felt the difficulty far too keenly to be surprised at others hesitating to extend the prin- ciple of natural selection to so startling a length. It is scarcely possible to avoid comparing the eye with a telescope. We know that this instrument has been per- fected by the long-continued efforts of the highest human intellects ; and we naturally infer that the eye has been formed by a somewhat analogous process. But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man? If we must compare the eye to an optical instrument, we ought in imagination to take a thick Page 145. 112 DARWINISM STATED BY DARWIN HIMSELF. layer of transparent tissue, with spaces filled with fluid, and with a nerve sensitive to light beneath, and then sup- pose every part of this layer to be continually changing slowly in density, so as to separate into layers of different densities and thicknesses, placed at different distances from each other, and with the surfaces of each layer slowly changing in form. Further, we must suppose that there is a power, represented by natural selection or the sur- vival of the fittest, always intently watching each slight alteration in the transparent layers ; and carefully pre- serving each which, under varied circumstances, in any way or in any degree, tends to produce a distincter image. We must suppose each new state of the instrument to be multiplied by the million ; each to be preserved until a better one is produced, and then the old ones to be all destroyed. In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerr- ing skill each improvement. Let this process go on for millions of years; and during each year on millions of individuals of many kinds ; and may we not believe that a living optical instrument might thus be formed as su- perior to one of glass as the works of the Creator are to those of man ? VI. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. Origin of WE are thus brought to the question which Species, has been largely discussed by naturalists, name- Pape a: ly, whether species have been created at one or more points of the earth’s surface. Undoubtedly there are many cases of extreme difficulty in understanding how the same species could possibly have migrated from some one point to the several distant and isolated points where now found. Nevertheless the simplicity of the view that each species was first produced within a single region captivates the mind. He who rejects it rejects the vera causa of ordinary generation with subsequent migration, and calls in the agency of a miracle. It is universally admitted that in most cases the area inhabited by a species is continuous ; and that, when a plant or animal inhabits two points so distant from each other, or with an interval of such a nature, that the space could not have been easily passed over by migration, the fact is given as something remarkable and exceptional. The incapacity of migrating across a wide sea is more clear in the case of terrestrial mammals than perhaps with any other organic beings; and, accordingly, we find no inexplicable in- stances of the same mammals inhabiting distant points 114 DARWINISM STATED BY DARWIN HIMSELF. of the world. No geologist feels any difficulty in Great Britain possessing the same quadrupeds with the rest of Europe, for they were no doubt once united. But, if the same species can be produced at two separate points, why do we not find a single mammal common to Europe and Australia or South America? The conditions of life are nearly the same, so that a multitude of European animals and plants have become naturalized in America and Aus- tralia; and some of the aboriginal plants are identically the same at these distant points of the northern and southern hemispheres. ‘The answer, as I believe, is, that mammals have not been able to migrate, whereas some plants, from their varied means of dispersal, have mi- grated across the wide and broken interspaces. The great and striking influence of barriers of all kinds is intelligible only on the view that the great majority of species have been produced on one side, and have not been able to migrate to the opposite side. Some few families, many sub-families, very many genera, and a still greater number of sections of genera, are confined to a single region: and it has been observed by several naturalists that the most natural genera, or those genera in which the species are most closely related to each other, are generally confined to the same country, or, if they have a wide range, that their range is continuous. What a strange anomaly it would be, if a directly opposite rule were to prevail, when we go down one step lower in the series, namely, to the individuals of the same species, and these had not been, at least at first, confined to some one region ! Hence it seems to me, as it has to many other natu- ralists, that the view of each species having been produced in one area alone, and having subsequently migrated from that area as far as its powers of migration and subsistence GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 115 under past and present conditions permitted, is the most probable. Undoubtedly many cases occur, in which we can not explain how the same species could have passed from one point to the other. But the geographical and climatal changes, which have certainly occurred within recent geological times, must have rendered discontinuous the formerly continuous range of many species. So that we are reduced to consider whether the exceptions to con- tinuity of range are so numerous and of so grave a nature that we ought to give up the belief, rendered probable by general considerations, that each species has been pro- duced within one area, and has migrated thence as far as it could. ISOLATED CONTINENTS NEVER WERE UNITED. Origin of Whenever it is fully admitted, as it will aoa some day be, that each species has proceeded from a single birthplace, and when in the course of time we know something definite about the means of distribution, we shall be enabled to speculate with security on the former extension of the land. But Ido not believe that it will ever be proved that within the recent period most of our continents which now stand quite separate have been continuously, or almost continuously, united with each other, and with the many existing oceanic islands. Several facts in distribution, such as the great difference in the marine faunas on the opposite sides of almost every continent, the close rela- tion of the tertiary inhabitants of several lands and even seas to their present inhabitants, the degree of affinity between the mammals inhabiting islands with those of the nearest continent, being in part determined (as we shall hereafter see) by the depth of the intervening ocean, these and other such facts are opposed to the admission 116 DARWINISM STATED BY DARWIN HIMSELF. of such prodigious geographical revolutions within the recent period as are necessary on the view advanced by Forbes and admitted by his followers. The nature and relative proportions of the inhabitants of oceanic islands are likewise opposed to the belief of their former con- tinuity with continents. Nor does the almost universally volcanic composition of such islands favor the admission that they are the wrecks of sunken continents; if they had originally existed as continental mountain-ranges, some at least of the islands would have been formed, like other mountain-summits, of granite, metamorphic schists, old fossiliferous and other rocks, instead of consisting of mere piles of volcanic matter. MEANS OF DISPERSAL. Living birds can hardly fail to be highly effective agents in the transportation of seeds. T could give many facts showing how frequently birds of many kinds are blown by gales to vast distances across the ocean. We may safely assume that under such cir- cumstances their rate of flight would often be thirty-five miles an hour ; and some authors have given a far higher estimate. I have never seen an instance of nutritious seeds passing through the intestines of a bird ; but hard seeds of fruit pass uninjured through even the digestive organs of a turkey. In the course of two months I picked up in my garden twelve kinds of seeds out of the excrement of small birds, and these seemed perfect, and some of them, which were tried, germinated. But the following fact is more important : the crops of birds do not secrete gastric juice, and do not, as I know by trial, injure in the least the germination of seeds; now, after a bird has found and devoured a large supply of food, it Page 326. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 117 is positively asserted that all the grains do not pass into the gizzard for twelve or even eighteen hours. A bird in this interval might easily be blown to the distance of five hundred miles, and hawks are known to look out for tired birds, and the contents of their torn crops might thus readily get scattered. Some hawks and owls bolt their prey whole, and, after an interval of from twelve to twenty hours, disgorge pellets, which, as I know from experiments made in the Zodlogical Gardens, include seeds capable of germination. Some seeds of the oat, wheat, millet, canary, hemp, clover, and beet germinated after having been from twelve to twenty-one hours in the stomachs of different birds of prey; and two seeds of beet grew after having been thus retained for two days and fourteen hours. Fresh-water fish, I find, eat seeds of many land and water plants: fish are frequently de- voured by birds, and thus the seeds might be transported from place to place. I forced many kinds of seeds into the stomachs of dead fish, and then gave their bodies to fishing-eagles, storks, and pelicans; these birds, after an interval of many hours, either rejected the seeds in pel- lets or passed them in their excrement; and several of these seeds retained the power of germination. Certain seeds, however, were always killed by this process. Locusts are sometimes blown to great distances from the land ; I myself caught one three hundred and seventy miles from the coast of Africa, and have heard of others caught at greater distances. As icebergs are known to be sometimes loaded with earth and stones, and have even carried brushwood, bones, and the nest of a land-bird, it can hardly be doubted that they must occasionally, as suggested by Lyell, have transported seeds from one part Page '328. 118 DARWINISM STATED BY DARWIN HIMSELF. to another of the Arctic and Antarctic regions, and during the Glacial period from one part of the now temperate regions to another. In the Azores, from the large num- ber of plants common to Europe, in comparison with the species on the other islands of the Atlantic, which stand nearer to the mainland, and (as remarked by Mr. H. C. Watson) from their somewhat northern character in comparison with the latitude, I suspected that these islands had been partly stocked by ice-borne seeds during the Glacial epoch. THESE MEANS OF TRANSPORT NOT ACCIDENTAL. These means of transport are sometimes called accidental, but this is not strictly cor- rect ; the currents of the sea are not accidental, nor is the direction of prevalent gales of wind. It should be observed that scarcely any means of transport would carry seeds for very great distances: for seeds do not retain their vitality when exposed for a great length of time to the action of sea-water ; nor could they be long carried in the crops or intestines of birds. These means, how- ever, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or from island to island, or from a continent to a neighboring island, but not from one distant continent to another. The floras of distant continents would not by such means become min- gled ; but would remain as distinct as they now are. The currents, from their course, would never bring seeds from North America to Britain, though they might and do bring seeds from the West Indies to our western shores, where, if not killed by their very long immersion in salt-water, they could not endure our climate. Almost every year, one or two land-birds are blown across the whole Atlantic Page 329. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 119 Ocean, from North America to the western shores of Ire- land and England ; but seeds could be transported by these rare wanderers only by one means, namely, by dirt ad- hering to their feet or beaks, which is in itself a rare acci- dent. Even in this case, how small would be the chance of a seed falling on favorable soil and coming to maturity ! But it would be a great error to argue that, because a well- stocked island, like Great Britain, has not, as far as is known (and it would be very difficult to prove this), re- ceived within the last few centuries, through occasional means of transport, immigrants from Europe or any other continent, a poorly-stocked island, though standing more remote from the mainland, would not receive col- onists by similar means. Out of a hundred kinds of seeds or animals transported to an island, even if far less well- stocked than Britain, perhaps not more than one would be so well fitted to its new home as to become natural- ized. But this is no valid argument against what would be effected by occasional means of transport, during the long lapse of geological time, while the island was being upheaved, and before it had become fully stocked with inhabitants. On almost bare land, with few or no de- structive insects or birds living there, nearly every seed which chanced to arrive, if fitted for the climate, would germinate and survive. DISPERSAL DURING THE GLACIAL PERIOD. The Glacial period is defined ‘‘as a period of great cold and of enormous extension of ice upon the surface of the earth. It is believed that glacial periods have occurred repeatedly during the geological history of the earth, but the term is generally applied to the close of the Tertiary epoch, when nearly the whole of Europe was subjected to an Arctic climate.” Page 434, 120 DARWINISM STATED BY DARWIN HIMSELF. Origin of The identity of many plants and animals, Species, on mountain-summits, separated from each page 330. other by hundreds of miles of lowlands, where Alpine species could not possibly exist, is one of the most striking cases known of the same species living at distant points, without the apparent possibility of their having migrated from one point to the other. It is imdeed a remarkable fact to see so many plants of the same species living on the snowy regions of the Alps or Pyrenees, and in the extreme northern parts of Europe; but it is far more remarkable that the plants on the White Mountains, in the United States of America, are all the same with those of Labrador, and nearly all the same, as we hear from Asa Gray, with those on the loftiest mountains of Europe. Even as long ago as 1747 such facts led Gmelin to conclude that the same species must have been inde- pendently created at many distinct points ; and we might have remained in this same belief, had not Agassiz and others called vivid attention to the Glacial period, which, as we shall immediately see, affords a simple explanation of these facts. We have evidence of almost every con- ceivable kind, organic and inorganic, that, within a very recent geological period, Central Europe and North Amer- ica suffered under an Arctic climate. The ruins of a house burned by fire do not tell their tale more plainly than do the mountains of Scotland and Wales, with their scored flanks, polished surfaces, and perched bowlders, of the icy streams with which their valleys were lately filled. So greatly has the climate of Europe changed, that in Northern Italy gigantic moraines, left by old glaciers, are now clothed by the vine and maize. Throughout a large part of the United States erratic bowlders and scored rocks plainly reveal a former cold period. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 121 The former influence of the glacial climate on the dis- tribution of the inhabitants of Europe, as explained by Edward Forbes, is substantially as follows. But we shall follow the changes more readily by supposing a new gla- cial period slowly to come on, and then pass away, as formerly occurred. As the cold came on, and as each more southern zone became fitted for the inhabitants of the north, these would take the places of the former in- habitants of the temperate regions. The latter, at the same time, would travel farther and farther southward, unless they were stopped by barriers, in which case they would perish. The mountains would become covered with snow and ice, and their former Alpine inhabitants would descend to the plains. By the time that the cold had reached its maximum, we should have an Arctic fauna and flora, covering the central parts of Europe, as far south as the Alps and Pyrenees, and even stretching into Spain. The now temperate regions of the United States would likewise be covered by Arctic plants and animals, and these would be nearly the same with those of Europe ; for the present circumpolar inhabitants, which we suppose to have everywhere traveled southward, are remarkably uniform round the world. As the warmth returned, the Arctic forms would re- treat northward, closely followed up in their retreat by the productions of the more temperate regions. And, as the snow melted from the bases of the mountains, the Arctic forms would seize on the cleared and thawed ground, always ascending, as the warmth increased and the snow still further disappeared, higher and higher, while their brethren were pursuing their northern journey. Hence, when the warmth had fully returned, the same species, which had lately lived together on the European and North American lowlands, would again be found in the 122 DARWINISM STATED BY DARWIN HIMSELF. Arctic regions of the Old and New Worlds, and on many isolated mountain-summits far distant from each other. Thus we can understand the identity of many plants at points so immensely remote as the mountains of the United States and those of Europe. THE THEORY OF CREATION INADEQUATE. As on the land, so in the waters of the sea, a slow southern migration of a marine fauna, which, during the Pliocene or even a somewhat earlier period, was nearly uniform along the continuous shores of the Polar Circle, will account, on the theory of modifica- tion, for many closely allied forms now living in marine areas completely sundered. Thus, I think, we can under- stand the presence of some closely allied, still existing and extinct tertiary forms on the eastern and western shores of temperate North America; and the still more striking fact of many closely allied crustaceans (as described in Dana’s admirable work), some fish and other marine ani- mals, inhabiting the Mediterranean and the seas of Japan —these two areas being now completely separated by the breadth of a whole continent and by wide spaces of ocean. These cases of close relationship in species either now or formerly inhabiting the seas on the eastern and west- ern shores of North America, the Mediterranean and Japan, and the temperate lands of North America and Europe, are inexplicable on the theory of creation. We can not maintain that such species have been created alike, in correspondence with the nearly similar physical conditions of the areas ; for, if we compare, for instance, certain parts of South America with parts of South Africa or Australia, we see countries closely similar in all their physical conditions, with their inhabitants utterly dis- similar. Page 334. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 123 CAUSES OF A GLACIAL CLIMATE. Mr. Croll, in a series of admirable memoirs, has attempted to show that a glacial condition of climate is the result of various physical causes, brought into operation by an increase in the eccentricity of the earth’s orbit. All these causes tend toward the same end ; but the most powerful appears to be the indirect influence of the eccentricity of the orbit upon oceanic currents. According to Mr. Croll, cold periods regularly recur every ten to fifteen thousand years ; and these at long intervals are extremely severe, owing to certain contingencies, of which the most important, as Sir C. Lyell has shown, is the relative position of the land and water. Mr. Croll believes that the last great Glacial period occurred about two hundred and forty thousand years ago, and endured with slight alterations of climate for about one hundred and sixty thousand years. With respect to more ancient Glacial periods, several geologists are convinced from di- rect evidence that such occurred during the Miocene and Eocene formations, not to mention still more ancient for- mations. But the most important result for us, arrived at by Mr. Croll, is that, whenever the northern hemisphere passes through a cold period, the temperature of the southern hemisphere is actually raised, with the winters rendered much milder, chiefly through changes in the direction of the ocean-currents. So conversely it will be with the northern hemisphere, while the southern passes through a glacial period. This conclusion throws so much light on geographical distribution that Iam strong- ly inclined to trust in it. Page 336. 124 DARWINISM STATED BY DARWIN HIMSELF. DIFFICULTIES NOT YET REMOVED. T am far from supposing that all the diffi- culties in regard to the distribution and affini- ties of the identical and allied species, which now live so widely separated in the north and south, and sometimes on the intermediate mountain-ranges, are removed on the views above given. The exact lines of migration can not be indicated. We can not say why certain species and not others have migrated ; why certain species have been modified and have given rise to new forms, while others have remained unaltered. We can not hope to explain such facts, until we can say why one species and not an- other becomes naturalized by man’s agency in a foreign land; why one species ranges twice or thrice as far, and is twice or thrice as common, as another species within their own homes. Various special difficulties also remain to be solved ; for instance, the occurrence, as shown by Dr. Hooker, of the same plants at points so enormously remote as Ker- guelen Land, New Zealand, and Fuegia; but icebergs, as suggested by Lyell, may have been concerned in their dispersal. The existence at these and other distant points of the southern hemisphere of species which, though distinct, belong to genera exclusively confined to the south, is a more remarkable case. Some of these species are so distinct that we can not suppose that there has been time since the commencement of the last Glacial period for their migration and subsequent modification to the necessary degree. The facts seem to indicate that distinct species belonging to the same genera have mi- grated in radiating lines from a common center; and I am inclined to look in the southern, as in the northern hemisphere, to a former and warmer period, before the Page 341. GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 125 commencement of the last Glacial period, when the Ant- arctic lands, now covered with ice, supported a highly peculiar and isolated flora. It may be suspected that, be- fore this flora was exterminated during the last Glacial epoch, a few forms had been already widely dispersed to various points of the southern hemisphere by occasional means of transport, and by the aid, as halting-places, of now sunken islands. Thus the southern shores of Amer- ica, Australia, and New Zealand, may have become slight- ly tinted by the same peculiar forms of life. IDENTITY OF THE SPECIES OF ISLANDS WITH THOSE OF THE MAINLAND EXPLAINED ONLY BY THIS THEORY. Origin of The most striking and important fact for ice us is the affinity of the species which inhabit islands to those of the nearest mainland, with- out being actually the same. Numerous instances could be given. The Galapagos Archipelago, situated under the equator, lies at the distance of between five hundred and six hundred miles from the shores of South America. Here almost every product of the land and of the water bears the unmistakable stamp of the American Continent. There are twenty-six land-birds ; of these, twenty-one or perhaps twenty-three are ranked as distinct species, and would commonly be assumed to have been here created ; yet the close affinity of most of these birds to American species is manifest in every character, in their habits, gestures, and tones of voice. So it is with the other ani- mals, and with a large proportion of the plants, as shown by Dr. Hooker in his admirable Flora of this archipelago. The naturalist, looking at the inhabitants of these vol- canic islands in the Pacific, distant several hundred miles from the continent, feels that he is standing on American 126 DARWINISM STATED BY DARWIN HIMSELF. land. Why should this be so? why should the species which are supposed to have been created in the Galapagos Archipelago, and nowhere else, bear so plainly the stamp of affinity to those created in America ? There is nothing in the conditions of life, in the geological nature of the islands, in their height or climate, or in the proportions in which the several classes are associated together, which closely resembles the conditions of the South American coast ; in fact, there is a considerable dissimilarity in all these respects. On the other hand, there is a consider- able degree of resemblance in the volcanic nature of the soil, in the climate, height, and size of the islands, be- tween the Galapagos and Cape de Verd Archipelagos ; but what an entire and absolute difference in their inhab- itants! The inhabitants of the Cape de Verd Islands are related to those of Africa, like those of the Galapagos to America. Facts such as these admit of no sort of ex- planation on the ordinary view of independent creation ; whereas, on the view here maintained, it is obvious that the Galapagos Islands would be likely to receive colonists from America, whether by occasional means of transport or (though I do not believe in this doctrine) by formerly continuous land, and the Cape de Verd Islands from Africa ; such colonists would be liable to modification, the principle of inheritance still betraying their original birthplace. Many analogous facts could be given : indeed, it is an almost universal rule that the endemic productions of islands are related to those of the nearest continent, or of the nearest large island. The exceptions are few, and most of them can be explained. Thus, although Ker- guelen Land stands nearer to Africa than to America, the plants are related, and that very closely, as we know from Dr. Hooker’s account, to those of America: but, on the GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS. 197 view that this island has been mainly stocked by seeds brought with earth and stones on icebergs, drifted by the prevailing currents, this anomaly disappears. New Zea- land in its endemic plants is much more closely related to Australia, the nearest mainland, than to any other re- gion : and this is what might have been expected ; but it is also plainly related to South America, which, al- though the next nearest continent, is so enormously re- mote that the fact becomes an anomaly. But this diffi- culty partially disappears on the view that New Zealand, South America, and the other southern lands have been stocked in part from a nearly intermediate though distant point, namely, from the Antarctic islands, when they were clothed with vegetation, during a warmer tertiary period, before the commencement of the last Glacial period. The affinity, which, though feeble, Iam assured by Dr. Hooker is real, between the flora of the southwestern corner of Australia and of the Cape of Good Hope, is a far more remarkable case; but this affinity is confined to the plants, and will, no doubt, some day be explained. VIL. EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM. The Descent HE who wishes to decide whether man is of _ the modified descendant of some pre-exist- page 5. ing form would probably first inquire whether man varies, however slightly, in bodily structure and in mental faculties ; and, if so, whether the variations are transmitted to his offspring in accordance with the laws which prevail with the lower animals. Again, are the variations the result, as far as our ignorance permits us to judge, of the same general causes, and are they governed by the same general laws, as in the case of other organ- isms ; for instance, by correlation, the inherited effects of use and disuse, etc. ? Is man subject to similar malcon- formations, the result of arrested development, of redu- plication of parts, etc., and does he display in any of his anomalies reversion to some former and ancient type of structure ? It might also naturally be inquired whether man, like so many other animals, has given rise to vari- eties and sub-races, differing but slightly from each other, or to races differing so much that they must be classed as doubtful species. How are such races distributed over the world ; and how, when crossed, do they react on each other in the first and succeeding generations ? And so with many other points. DESCENT OF MAN FROM SOME LOWER FORM. 129 The inquirer would next come to the important point whether man tends to increase at so rapid a rate as to lead to occasional severe struggles for existence ; and_conse- quently to beneficial variations, whether in body or mind, being preserved, and injurious ones éliminated. Do the races or species of men, whichever term may be applied, encroach on and replace one another, so that some finally become extinct ? We shall see that all these questions, as indeed is obvious in respect to most of them, must be answered in the affirmative, in the same manner as with the lower animals. POINTS OF CORRESPONDENCE BETWEEN MAN AND THE OTHER ANIMALS, The Descent It is notorious that man is constructed o of a the same general type_o .ag other.mam- page 6. mals. All the bones in his skeleton can be compared with corresponding bones in a monkey, bat, or seal. So it is with his muscles, nerves, blood-vessels, and internal viscera. The brain, the most important of all the organs, follows the same law, as 7 a8 Shown by Huxley anc and other anatomists. Bischoff, who is a hostile witness, ad- mits that every chief fissure and fold in the brain of man has its analogy in that of the orang; but he adds that at no period of development do their brains perfectly agree ; nor could perfect agreement be expected, for otherwise their mental powers would have been the same. Man is liable to receive from the lower animals, and to communicate to them, certain diseases, as hydropho- bia, variola, the glanders, syphilis, cholera, herpes, etc. ; and this fact proves the close similarity of their tissues and blood, both in minute structure and composition, far more plainly than does their comparison under the best vg 130 DARWINISM STATED BY DARWIN HIMSELF. microscope, or by the aid of the best chemical analysis. Monkeys are liable to many of the same non-contagious diseases as we are ; thus Rengger, who carefully observed for a long time the Cebus Azar@ in its native land, found it liable to catarrh, with the usual symptoms, and which, when often recurrent, led to consumption. These mon- keys suffered also from apoplexy, inflammation of the bowels, and cataract in the eye. The younger ones when shedding their milk-teeth often died from fever. Medi- cines produced the same effect on them as onus. Many kinds of monkeys have a strong taste for tea, coffee, and spirituous liquors: they will also, as I have myself seen, smoke tobacco with pleasure. Brehm asserts that the \natives of Northeastern Africa catch the wild baboons by /exposing vessels with strong beer, by which they are made ‘drunk. He has seen some of these animals, which he kept in confinement, in this state ; and he gives a laugha- ble account of their behavior and strange grimaces. On the following morning they were very cross and dismal ; they held their aching heads with both hands, and wore a most pitiable expression : when beer or wine was offered them, they turned away with disgust, but relished the juice of lemons. An American monkey, an Ateles, after getting drunk on brandy, would never touch it again, and thus was wiser than many men. These trifling facts prove how similar the nerves of taste must-bein monkeys and man, and how similarly their whole nervous system is affected. Man is infested with internal parasites, sometimes causing fatal effects; and is plagued by external para- sites, all of which belong to the same genera or families as those infesting other mammals, and in the case of scabies to the same species. Man is subject, like other mammals, birds, and even insects, to that mysterious law DESCENT OF MAN FROM SOME LOWER FORM. 131 which causes certain normal processes, such as gestation, as well as the maturation and duration of various dis- eases, to follow lunar periods. His wounds are repaired by the same process of healing ; and the stumps left after the amputation of his limbs, especially during an early embryonic period, occasionally possess some power of re- generation, as in the lowest animals. Man is developed from an ovule, about the 125th of an inch in diameter, which differs in no respect from the ovules of other animals. The embryo itself at a very early period can hardly be distinguished from that of other members of the vertebrate kingdom. At this period the arteries run in arch-like branches, as if to carry the blood to branchiz which are not present in the higher vertebrata, though the slits on the side of the neck still remain, marking their former position. Ata. somewhat later period, when the extremities are developed, - “