Life of Charles Darwin Part 5

CHAPTER VIII.

"The Expression of the Emotions in Man and Animals" followed "The Descent of Man" in 1872. The motive which suggested it was the desire to explain the complexities of expression on evolution principles. But the study of emotional expression had evidently engaged Darwin's attention at least from the time when the Fuegians and the Gauchos had vividly roused his imaginative faculties; and his direct observations commenced as early as 1838; when he was already inclined to believe in evolution, and were continued at intervals ever after. The third edition of Sir Charles Bell's "Anatomy of Expression," published in 1844, while greatly admired by him, was unsatisfactory in being throughout based on the conviction that species came into existence in their present condition; and notwithstanding that Bain and Herbert Spencer had made considerable advances in a treatment of the subject based on physiology, an exhaustive book was wanted, which should throw on Expression the new and interesting light of Darwinism.

What was Darwin's method? Observation, cleverly devised appeal to nature; observation over a wide field as to the varied races of man still existing, utilising the aid of travellers and residents in many lands; observation of domestic animals in familiar and in untried circ.u.mstances; observation of infants, especially his own, from a very early age; observation of the insane, who are liable to the strongest pa.s.sions, and give them uncontrolled vent. It was in 1867 that Darwin circulated his group of questions designed to ascertain the mode of expressing every emotion, and their physical concomitants in every possible race. Sculpture, paintings, and engravings, afforded little evidence, because beauty is their main object, and "strongly contracted facial muscles destroy beauty." Information was specially sought as to natives who had had little communication with Europeans, and in whom imitation might not have destroyed ancestral and original expression.

The result was to develop three principles which appeared, in combination, to account for most of the expressions and gestures involuntarily used by man and animals. The first was that of serviceable a.s.sociated habits: certain complex actions being somehow serviceable in particular states of mind, to gratify and relieve certain sensations, desires, &c., whenever the same state of feeling is repeated, there is a tendency to the same movements or actions, though they may not then be of the least use. The second principle, that of ant.i.thesis, is the converse of the last; when an opposite state of mind is induced, there is an involuntary tendency to directly opposite movements, though of no use. The third principle, that of the direct action of the nervous system, is independent of the will and of habit; nerve force being generated in excess by strong emotions.

In discussing all these principles we discover how every thought and every circ.u.mstance of the great naturalist seem to have been utilised in his life work. "I have noticed that persons in describing a horrid sight, often shut their eyes momentarily and firmly, or shake their heads as if not to see, or to drive away, something disagreeable; and I have caught myself, when thinking in the dark of a horrid spectacle, closing my eyes firmly." "I noticed a young lady earnestly trying to recollect a painter's name, and she first looked to one corner of the ceiling, and then to the opposite corner, arching the one eyebrow on that side, although of course there was nothing to be seen there." "Many years ago I laid a small wager with a dozen young men that they would not sneeze if they took snuff, although they all declared that they invariably did so; accordingly they all took a pinch, but from wishing much to succeed, not one sneezed, though their eyes watered, and all, without exception, had to pay me the wager." "I put my face close to the thick gla.s.s-plate in front of a puff-adder in the Zoological Gardens, with the firm determination of not starting back if the snake struck at me; but as soon as the blow was struck, my resolution went for nothing, and I jumped a yard or two backwards with astonishing rapidity. My will and reason were powerless against the imagination of a danger which had never been experienced." "I observed that though my infants started at sudden sounds, when under a fortnight old, they certainly did not always wink their eyes, and I believe never did so. The start of an older infant apparently represents a vague catching hold of something to prevent falling. I shook a pasteboard box close before the eyes of one of my infants, when 114 days old, and it did not in the least wink; but when I put a few comfits into the box, holding it in the same position as before, and rattled them, the child blinked its eyes violently every time, and started a little." The behaviour of dogs and horses under many circ.u.mstances was watched. Cats and monkeys were most carefully scrutinised. At all moments Darwin seized upon and recorded the pa.s.sing emotion and its a.s.sociated movements. "I remember once seeing a boy who had just shot his first snipe on the wing, and his hands trembled to such a degree from delight, that he could not for some time reload his gun;" an instance of an emotional movement being disadvantageous.

Some of Darwin's descriptions of emotional outbursts are among the best portions of his writing; as when he speaks of a mother whose infant has been intentionally injured, "how she starts up with threatening aspect, how her eyes sparkle and her face reddens, how her bosom heaves, nostrils dilate, and heart beats." In describing a mourner when quiescent, he says: "The sufferer sits motionless, or gently rocks to and fro; the circulation becomes languid; respiration is almost forgotten, and deep sighs are drawn. All this reacts on the brain, and prostration soon follows with collapsed muscles and dulled eyes."

One of the most striking features of this book is the evidence it affords of Darwin's acuteness and persistence in observation during his travels, and of the excellence of his memory. "I remember that my mules and dogs, brought from a lower and warmer country, after spending a night on the bleak Cordillera, had the hair all over their bodies as erect as under the greatest terror." He noted that Jemmy b.u.t.ton, the Fuegian, blushed when he was quizzed about the care which he took in polishing his shoes, and in otherwise adorning himself; and this fact long after is fitted into the theory of blushing. Guanacoes in South America, when not intending to bite, but merely to spit their offensive saliva from a distance at an intruder, yet retract their ears as a sign of their anger; and Darwin found the hides of several which he shot in Patagonia, deeply scored by teeth marks, in consequence of their battles with each other. A party of natives in Tierra del Fuego endeavoured to explain that their friend, the captain of a sealing vessel, was out of spirits, by pulling down their cheeks with both hands, so as to make their faces as long as possible; and the fact is treasured till it comes in to ill.u.s.trate the lengthening of features under depression. As if he foreknew that he should want the fact forty years later, he inquired of Jemmy b.u.t.ton whether kissing was practised by his people, and learnt that it was unknown to them. "I remember," he says, "being struck whilst travelling in parts of South America, which were dangerous from the presence of Indians, how incessantly--yet as it appeared, unconsciously--the half-wild Gauchos closely scanned the whole horizon."

"In Tierra del Fuego, a native touched with his finger some cold preserved meat which I was eating at our bivouac, and plainly showed utter disgust at its softness; whilst I felt utter disgust at my food being touched by a naked savage, though his hands did not appear dirty."

And this ill.u.s.trates the primary meaning of disgust--anything offensive to the taste.

In later years his own children, and his domestic pets, were incessantly watched, and suitable experiments were devised to bring out the real nature of their expressions. The period at which tears are formed and crying begins, the shape of the mouth in crying, the contraction of the muscles in shouting, the effects of steady gazing at objects, the various stages of smiling, the effects of shyness, shame, and fear, are all set before us, as thus observed. For instance, "I asked one of my boys to shout as loudly as he possibly could, and as soon as he began he firmly contracted his...o...b..cular muscles (surrounding the eyes). I observed this repeatedly, and on asking him why he had every time so firmly closed his eyes, I found that he was quite unaware of the fact: he had acted instinctively or unconsciously." Some of his early observations were afterwards published by Darwin in _Mind_, vol. ii., under the t.i.tle of "A Biographical Sketch of an Infant."

Here is a carefully-worded and very suggestive experiment on animals: "Many years ago, in the Zoological Gardens, I placed a looking-gla.s.s on the floor before two young orangs, who, as far as it was known, had never before seen one. At first they gazed at their own images with the most steady surprise, and often changed their point of view. They then approached close, and protruded their lips towards the image, as if to kiss it, in exactly the same manner as they had previously done towards each other when first placed, a few days before, in the same room. They next made all sorts of grimaces, and put themselves in various att.i.tudes before the mirror; they pressed and rubbed the surface; they placed their hands at different distances behind it; looked behind it; and finally seemed almost frightened, started a little, became cross, and refused to look any longer." So monkeys were tested with a dressed doll, a live turtle, and stuffed snakes, &c.

The mode and purpose of erection of the hair, feathers, and dermal appendages of animals were the subject of much careful inquiry.

Chimpanzees, monkeys, baboons, and many other creatures, were tested in the Zoological Gardens. A stuffed snake taken into the monkey-house caused several species to bristle. When Darwin showed the same to a peccary, the hair rose in a wonderful manner along its back. A ca.s.sowary erected its feathers at sight of an ant-eater.

Every unexpected occurrence was pressed into service. Witness the following anecdote: "One day my horse was much frightened at a drilling machine, covered by a tarpaulin and lying on an open field. He raised his head so high that his neck became almost perpendicular; and this he did from habit, for the machine lay on a slope below, and could not have been seen with more distinctness through the raising of the head; nor if any sound had proceeded from it could the sound have been more distinctly heard. His eyes and ears were directed intently forwards; and I could feel through the saddle the palpitations of his heart. With red, dilated nostrils, he snorted violently, and whirling round, would have dashed off at full speed had I not prevented him."

We see, too, in this book the results of Darwin's extensive reading.

The novelists are laid considerably under contribution, their power of describing expressive signs of emotion being particularly appreciated.

d.i.c.kens, Walter Scott, Mrs. Oliphant, and Mrs. Gaskell are among the novelists quoted; while the author of Job, Homer, Virgil, Seneca, Shakespeare, Lessing, Sir Joshua Reynolds, and many other deceased writers, ill.u.s.trate the subject. The living authorities--scientific men, travellers, doctors--referred to for facts are exceedingly numerous, including Sir James Paget, Professor Huxley, Mr. Herbert Spencer, Sir J.

Crichton Browne, Sir Samuel Baker, Sir Joseph Lister, Professors Cope and Asa Gray, and many others.

One of the most interesting chapters in the book is that dealing with blushing. It is shown to depend on self-attention, excited almost exclusively by the opinion of others. "Every one feels blame more acutely than praise. Now, whenever we know, or suppose, that others are depreciating our personal appearance, our attention is strongly drawn towards ourselves, more especially to our faces." This excites the nerve centres receiving sensory nerve for the face, and in turn relaxes the blood capillaries, and fills them with blood. "We can understand why the young are much more affected than the old, and women more than men, and why the opposite s.e.xes especially excite each others' blushes. It becomes obvious why personal remarks should be particularly liable to cause blushing, and why the most powerful of all the causes is shyness; for shyness relates to the presence and opinion of others, and the shy are always more or less self-conscious."

One great result made clear by Darwin is that the muscles of expression have not been created or developed for the sake of expression only, and that every true or inherited movement of expression had some natural or independent origin. All the chief expressions are proved to be essentially the same throughout the world, which is an additional argument for man being descended from one stock. We cannot refrain from admiring the tone of the pages which close the book, describing as they do the probable expressions of our early ancestors, their utility, the value of differences of physiognomy, and the desirability or otherwise of repressing signs of emotion. The subject, says the author, "deserves still further attention, especially from any able physiologist;" and so simply ends a volume of surpa.s.sing human interest, a text-book for novelists and students of human nature, a landmark in man's progress in obedience to the behest "Know thyself."

To fully measure the merit of one so far elevated above ordinary men is almost impossible; rather is it desirable to recognise the undeniable greatness of a great man, and learn all that is possible from him. An undoubted authority in mental science, however, has given a judgment on Darwin's services to that science, which it is right to quote: "To ourselves it almost seems one of the most wonderful of the many wonderful aspects of Mr. Darwin's varied work that by the sheer force of some exalted kind of common-sense, una.s.sisted by any special acquaintance with psychological method, he should have been able to strike, as it were, straight down upon some of the most important truths which have ever been brought to light in the region of mental science."[12] These truths are specified as the influence of natural selection in the formation of instinct, in the "Origin of Species;" the evolution of mind and of morals, in the "Descent of Man," considered by the late Professor Clifford as containing the simplest and clearest and most profound philosophy that was ever written on the subject; and the evolution of expression in the book described in this chapter. Thus, says Mr. Romanes, in respect both of instincts and intelligence, the science of comparative psychology may be said to owe its foundation to Darwin.

FOOTNOTES:

[12: G. J. Romanes, in "Charles Darwin," memorial notices reprinted from _Nature_.]

CHAPTER IX.

In 1875 appeared another great work from the master's pen, "Insectivorous Plants," which was destined to place in a yet more striking light the many-sidedness and fertility of his mind. As usual Darwin tells us that this work dated from many years back. "During the summer of 1860," he says, "I was surprised by finding how large a number of insects were caught by the leaves of the common sun-dew (_Drosera rotundifolia_) on a heath in Suss.e.x. I had heard that insects were thus caught, but knew nothing further on the subject. I gathered by chance a dozen plants, bearing fifty-six fully expanded leaves, and on thirty-one of these dead insects or remnants of them adhered." Here was the germ of something, the discoverer scarcely knew what. It was evident to him that the little sun-dew was excellently adapted for catching insects, and that the number of them thus slaughtered annually must be enormous. What bearing might this have upon the problem of the struggle for existence?

A masterly series of experiments was forthwith set on foot, with the result of proving that sun-dews and a number of other plants obtain the bulk of their nourishment by catching, killing, and digesting insects.

They may be called truly carnivorous plants. What an unexpected reversal this was of the order of things. .h.i.therto believed to prevail universally. Animals live on other animals or on plants. Here were plants living on animals, and keeping down their number. Moreover, without a nervous system, the action of the parts of a sun-dew leaf was proved to be as apparently purposive as the combined action of the limbs of an animal. Without a stomach, the sun-dew poured forth a digestive fluid as effective in extracting and fitting the nutritious matter of the insect for its own purposes as that of an animal. Without sensory nerve-endings, there was a percipient power in the sun-dew which recognised instinctively and at once the non-nutritious nature of various objects, and which responded to the most delicate chemical stimuli and to the minutest weights.

We cannot describe the little sun-dew better than in Darwin's own words: "It bears from two or three to five or six leaves, generally extended more or less horizontally, but sometimes standing vertically upwards.

The leaves are commonly a little broader than long. The whole upper surface is covered with gland-bearing filaments, or tentacles as I shall call them from their manner of acting. The glands were counted on thirty-one leaves, but many of these were of unusually large size, and the average number was 192; the greatest number being 260, and the least 130. The glands are each surrounded by large drops of extremely viscid secretion, which, glittering in the sun, have given rise to the plant's poetical name of the sun-dew."

This secretion, when excited by nutritious matter, becomes distinctly acid, and contains a digestive ferment allied to the pepsin of the human stomach. So excited, it is found capable of dissolving boiled white of egg, muscle, fibrin, cartilage, gelatine, curd of milk, and many other substances. Further, various substances that animal gastric juice is unable to digest are not acted upon by the secretion of the sun-dew.

These include all h.o.r.n.y matter, starch, fat, and oil. It is not however prejudiced in favour of animal matter. The sun-dew can absorb nutriment from living seeds of plants, injuring or killing them, of course, in the process, while pollen and fresh green leaves yield to its influence.

The action of salts of ammonia and other chemicals was even more wonderful. "It is an astonishing fact that so inconceivably minute a quant.i.ty as the one twenty-millionth of a grain of phosphate of ammonia should induce some change in a gland of Drosera sufficient to cause a motor impulse to be sent down the whole length of the tentacle; this impulse exciting movement often through an angle of above 180. I know not whether to be most astonished at this fact, or that the pressure of a minute bit of hair, weighing only 1/78700 of a grain, and largely supported by the dense secretion, should quickly cause conspicuous movement."

These are but specimens of a mult.i.tude of profoundly interesting facts brought out in this exhaustive investigation. If this single research were his only t.i.tle to fame Darwin's name must rank high as an experimenter of rare ingenuity and success. But he concludes his summary of results by the utterly modest remark, "We see how little has been made out in comparison with what remains unexplained and unknown."

The facts relating to Venus' fly-trap (_Dionaea muscipula_) and other members of the order to which the sun-dew belongs were better known, but Darwin elicited new truths by his ingenious and varied experiments. The rapidity with which the two lobes of the leaf of dionaea close together when anything touches the tiny spikes which stand up vertically from the upper surface of the lobes, is astonishing, and any insect which causes the closure is almost certain to be caught. Digestion is accomplished in the case of the dionaea by a separate agency, consisting of a large number of minute reddish glands covering the surface of the lobes. These secrete a digestive fluid when stimulated by the contact of any nitrogenous matter, and of course this takes place when any insect is caught. In fact, essentially the same process of digestion and absorption takes place as in the sun-dew. The insect is held firmly for days, until its juices have been absorbed, and then the leaf slowly reopens, not being able to close again for many subsequent days.

It is interesting to note the extreme caution with which the great naturalist speculates upon the mode by which the varied members of the sun-dew order became modified from an ordinary plant-form to such a remarkable degree. The details are too special for quotation here. He suggests, but he does not in the slightest degree dogmatise. For many years to come Darwin's suggestions and comments must be the pregnant soil out of which fruitful research will spring, and his caution will remain the model, to depart from which will but sow hindrances in the path of scientific progress.

The order to which the b.u.t.terwort and the bladderworts belong also afforded valuable results. The leaf of the b.u.t.terwort bears glandular hairs, and its margins curve inwards when excited by contact of various bodies, especially living insects, and, at the same time, these are caught in the viscid secretion of the glands, and their juices absorbed by the plant. The bladderworts are even more remarkably constructed, for they have a portion of their leaves developed into subaqueous bladders, with a narrow entrance beneath, defended by a complex valve, which facilitates the entrance of water insects or crustaceans, but prevents their exit. The whole interior of the bladder is lined with transparent four-branched protoplasmic hairs, but nevertheless the bladderwort is unlike the preceding plants in having no power of digesting its prey, however long it may remain in captivity. Yet there is no doubt that the imprisoned creatures do decay in their watery cell, and that the hairs just described absorb the products of their decay.

Such is a brief account of Darwin's work on "Insectivorous Plants." With his characteristic expressions he acknowledges the valuable aid given him by Professor Burdon-Sanderson, and by his son, Mr. Francis Darwin.

The former was enabled to give the first brief account of the process of digestion in these plants, as observed by Darwin, in a lecture before the Royal Inst.i.tution, in June, 1874, and Dr. (now Sir Joseph) Hooker called general public notice to the subject of Carnivorous Plants in his lecture before the British a.s.sociation at Belfast in the same year: so that a thoroughly awakened attention was given to this new work from Darwin's pen. The public and the scientific world learnt to appreciate yet more keenly his varied talent, his long patience, his reserve of power; and thence dated very definitely a general appreciation of the fundamental unity of the animal and plant kingdoms, seeing that the salient faculties of digestion, of purposive locomotion, of rapid communication and consentaneous action were no longer restricted to animals, but were possessed in a high degree by plants also. Eager followers soon brought forward further proofs of unity of functions in the two kingdoms, and of reciprocal combinations between them, and now no one in the slightest degree acquainted with modern biology doubts that life is at bottom one phenomenon, shared equally and manifested in essentially the same modes by the living substance of plant and animal alike.

Following "Insectivorous Plants" came "The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom," in 1876. Darwin had led the way in the study of this subject by his book on Orchids, and his lead had been excellently followed by Hildebrand, Hermann Muller, Sir John Lubbock, and others. The path having been indicated, it had appeared comparatively easy for botanists to follow it up. But there yet remained a region of experimental inquiry which it required Darwin's patience and ingenuity to master and to expound conclusively. Although it might be practically granted that natural selection developed a process because advantage was gained by it, was it possible to demonstrate that flowers cross-fertilised bear more and larger seeds, which produce healthier offspring than those fertilised from their own pollen? This Darwin set himself exhaustively to do. For more than a dozen years after his book on orchids appeared, unwearied experiments on plants were progressing, and nature was being questioned acutely, untiringly. Compet.i.tive germination was carried on. The two cla.s.ses of seeds were placed on damp sand in a warm room. As often as a pair germinated at the same time, they were planted on opposite sides of the same pot, with a part.i.tion between. Besides these pairs of compet.i.tors, others were planted in beds, so that the descendants of the crossed and self-fertilised flowers might compete. The resulting seeds were carefully compared, and their produce again compared. Species were selected from widely distinct families, inhabiting various countries.

From a large number of plants, when insects were quite excluded by a thin net covering the plant, few or no seeds were produced. The extent of transport of pollen by insects was unveiled, and the relation between the structure, odour, and conspicuousness of flowers, the visits of insects, and the advantages of cross-fertilisation was shown. "We certainly," says Darwin, "owe the beauty and odour of our flowers, and the storage of a large supply of honey, to the existence of insects."

The mult.i.tude of facts gathered about insects could only have been discovered and rightly appreciated by one who was a true entomologist as well as a botanist.

In the last chapter of the book the author discusses with remarkable power the causes of the phenomena he has discovered. He believes that the favourable effects of crossing are due to the parents having been subjected to diverse conditions; but what the precise benefit is, or how it can operate so as to render the offspring more healthy and vigorous, he cannot discern. "And so it is," he observes, "with many other facts, which are so obscure that we stand in awe before the mystery of life."

So it is. The man who probably understood nature better than any man who has ever lived, who had not only asked her mult.i.tudinous questions, but to whom very many answers had been undoubtedly vouchsafed in response to his persevering, humble, diligent, acute questioning, acknowledges that he knows little; that much remains a mystery. But from all we know of him, from his books, his letters, his friends, his was the joy of a soul in sympathy with the master power of the universe. He marched continually on the confines of the unknown, and to him was granted the felicity of largely extending the boundaries of the known.

Again, in 1877, a new work proceeded from Darwin's pen, "The Different Forms of Flowers in Plants of the same Species," dedicated to Professor Asa Gray. It gathered up the contents of numerous papers read before the Linnean Society, with later additions, and showed conclusively how many plants possess distinctive forms of flowers in the same species, adapted to, and in some cases absolutely necessitating, reciprocal fertilisation through the visits of insects. It gave evidence of all the well-known Darwinian characteristics of long-continued labour, thought, and experiment.

In 1880 "The Power of Movement in Plants" was exemplified in a fresh volume, in which the veteran was materially a.s.sisted by his son, Mr.

Francis Darwin. Its object was to describe and connect together several large cla.s.ses of movements, common to almost all plants. The surprising fact was established, that all the parts or organs of plants, whilst they continue to grow, are continually revolving, or circ.u.mnutating as Darwin called it. This movement commences even before the young seedling has broken through the ground. The combination of this with the effects of gravity and light explains countless phenomena in the life of plants.

The tip of the rootlet is thus enabled to penetrate the ground, and it is proved to be more sensitive than the most delicate tendril. Movement goes on through all stages of life. Every growing shoot of a great tree is continually describing small ellipses; the tip of every rootlet endeavours to do the same. The changes of position of leaves and of climbing plants, and the sleep of leaves are all brought under this great principle of circ.u.mnutation. It is impossible in reading the book not to be struck with the great resemblance between the movements of plants and many of the actions performed unconsciously by the lower animals. "With plants an astonishingly small stimulus suffices, and, even with allied plants, one may be highly sensitive to the slightest continued pressure, and another highly sensitive to a slight momentary touch. The habit of moving at certain periods is inherited both by plants and animals, and several other points of similitude have been specified. But the most striking resemblance is the localisation 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 transmission of impressions, and for the more complete intercommunication of the several parts."

Here we see how much light may be thrown on animal structures and functions by vegetable physiology. We learn to limit our ideas of the superiority of animals by discovering how much of what we consider peculiar to them is found in plants. We appreciate the unity of biology, indivisible without injury to our knowledge of its parts. No structure in plants appears more wonderful, as Darwin describes it, than the tip of the rootlet of a seedling. It is impressed by and transmits influences of pressure, injury, moisture, light, and gravity to other parts, and determines the course pursued by the rootlet in penetrating the ground. "It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals;"

and the brain of Charles Darwin, in working out this acquisition of knowledge for mankind, has added a new department to vegetable physiology and to biology.

CHAPTER X.

In his later years honours poured thick upon Darwin. In 1871 he received the Prussian order of knighthood "For Merit"; and was elected a corresponding member of the Austrian Academy of Sciences. In 1877 Cambridge University, making an exception to its custom of not conferring honorary degrees on its members, gave him the LL.D. and an ovation, when the kindly eyes of the venerable naturalist beamed upon the monkey-figure dangled by undergraduates before him from the galleries, in addition to a solitary link of a huge chain, no doubt representing "the missing link." In 1878 the honour, long withheld, and certainly unsought, of being elected a corresponding member of the Paris Academy of Sciences in the section of Zoology, was his; and that tardy body recognised late the man whose supremacy in science it had done nothing either to foster or to approve. In 1879 the Baly Medal of the London College of Physicians was awarded to him.

After the Cambridge celebration a subscription was raised to obtain a portrait of the veteran evolutionist, which was executed by Mr. W. B.

Richmond, and now adorns the Philosophical Library of the New Museums at Cambridge. Later, yet another portrait--the finest in his own and many others' belief--was painted by Mr. John Collier, and presented to the Linnean Society, which will always be a.s.sociated with the first announcement of Darwin's main theory, as well as with many others of his scientific discoveries.