Evolution, Old & New Part 16

"The approach of the anthers in many flowers to the stigmas, and of the pistils of some flowers to the anthers, must be ascribed to the pa.s.sion of love, and hence belongs to sensation, not to irritation.

"III. That the vegetable world possesses some degree of voluntary powers appears from their necessity to sleep, which we have shown in Section XVIII. to consist in the temporary abolition of voluntary power. This voluntary power seems to be exerted in the circular movement of the tendrils of the vines, and other climbing vegetables; or in the efforts to turn the upper surfaces of their leaves, or their flowers, to the light.

"IV. The a.s.sociations of fibrous motions are observable in the vegetable world as well as in the animal. The divisions of the leaves of the sensitive plant have been accustomed to contract at the same time from the absence of light; hence, if by any other circ.u.mstance, as a slight stroke or injury, one division is irritated into contraction, the neighbouring ones contract also from their motions being a.s.sociated with those of the irritated part. So the various stamina of the cla.s.s of syngenesia have been accustomed to contract together in the evening, and thence if you stimulate any one of them with a pin, according to the experiment of M. Colvolo, they all contract from their acquired a.s.sociations.

"To evince that the collapsing of the sensitive plant is not owing to any mechanical vibrations propagated along the whole branch when a single leaf is struck with the finger, a leaf of it was slit with sharp scissors, with as little disturbance as possible, and some seconds of time pa.s.sed before the plant seemed sensible of the injury, and then the whole branch collapsed as far as the princ.i.p.al stem. This experiment was repeated several times with the least possible impulse to the plant.

"V. 1. For the numerous circ.u.mstances in which vegetable buds are a.n.a.logous to animals, the reader is referred to the additional notes at the end of 'Botanic Garden,' Part I. It is there shown that the roots of vegetables resemble the lacteal system of animals; the sap vessels in the early spring, before their leaves expand, are a.n.a.logous to the placental vessels of the foetus; that the leaves of land plants resemble lungs, and those of aquatic plants the gills of fish; that there are other systems of vessels resembling the vena portarum of quadrupeds, or the aorta of fish; that the digestive power of vegetables is similar to that of animals converting the fluids which they absorb into sugar;[164] that their seeds resemble the eggs of animals, and their buds and bulbs their viviparous offspring; and lastly, that the anthers and stigmas are real animals attached to their parent tree like polypi or coral insects, but capable of spontaneous motion; that they are affected with the pa.s.sion of love, and furnished with powers of reproducing their species, and are fed with honey like the moths and b.u.t.terflies which plunder their nectaries.[165]

"The male flowers of Vallisneria approach still nearer to apparent animality, as they detach themselves from the parent plant, and float on the surface of the water to the female ones.[166] Other flowers of the cla.s.ses of monoecia and dioecia, and polygamia discharge the fecundating farina, which, floating in the air, is carried to the stigma of the female flowers, and that at considerable distances. Can this be effected by any specific attraction? Or, like the diffusion of the odorous particles of flowers, is it left to the currents of the winds, and the accidental miscarriages of it counteracted by the quant.i.ty of its production?

"2. This leads us to a curious inquiry, whether vegetables have ideas of external things? As all our ideas are originally received by our senses, the question may be changed to whether vegetables possess any organs of sense? Certain it is that they possess a sense of heat and cold, another of moisture and dryness, and another of light and darkness, for they close their petals occasionally from the presence of cold, moisture, or darkness. And it has been already shown that these actions cannot be performed simply from irritation, because cold and darkness are negative quant.i.ties, and on that account sensation, or volition are implied, and in consequence a sensorium or union of their nerves. So when we go into the light we contract the iris; not from any stimulus of the light on the fine muscles of the iris, but from its motions being a.s.sociated with the sensation of too much light upon the retina, which could not take place without a sensorium or centre of union of the nerves of the iris, with those of vision.[167]

"Besides these organs of sense, which distinguish cold, moisture, and darkness, the leaves of mimosa, and of dionaea, and of drosera, and the stamens of many flowers, as of the berbery, and the numerous cla.s.s of syngenesia, are sensible to mechanic impact, that is, they possess a sense of touch, as well as a common sensorium, by the medium of which their muscles are excited into action. Lastly, in many flowers the anthers, when mature, approach the stigma, in others the female organ approaches to the male. In a plant of collinsonia, a branch of which is now before me, the two yellow stamens are about three-eighths of an inch high, and diverge from each other at an angle of about fifteen degrees, the purple style is half an inch high, and in some flowers is now applied to the stamen on the right hand, and in others to that of the left; and will, I suppose, change place to-morrow in those, where the anthers have not yet effused their powder.

"I ask by what means are the anthers in many flowers and stigmas in other flowers directed to find their paramours? How do either of them know that the other exists in their vicinity? Is this curious kind of storge produced by mechanic attraction, or by the sensation of love? The latter opinion is supported by the strongest a.n.a.logy, because a reproduction of the species is the consequence; and then another organ of sense must be wanted to direct these vegetable amourettes to find each other, one probably a.n.a.logous to our sense of smell, which in the animal world directs the new-born infant to its source of nourishment, and they may thus possess a faculty of perceiving as well as of producing odours.

"Thus, besides a kind of taste at the extremity of their roots, similar to that of the extremities of our lacteal vessels, for the purpose of selecting their proper food, and besides different kinds of irritability residing in the various glands, which separate honey, wax, resin, and other juices from their blood; vegetable life seems to possess an organ of sense to distinguish the variations of heat, another to distinguish the varying degrees of moisture, another of light, another of touch, and probably another a.n.a.logous to our sense of smell. To these must be added the indubitable evidence of their pa.s.sion of love, and I think we may truly conclude that they are furnished with a common sensorium for each bud, and that they must occasionally repeat those perceptions, either in their dreams or waking hours, and consequently possess ideas of so many of the properties of the external world, and of their own existence."[168]

FOOTNOTES:

[155] 'Origin of Species,' note on p. xiv.

[156] 'Zoonomia,' vol. i. p. 170.

[157] Miss Seward's 'Memoirs,' &c., p. 491.

[158] See p. 116 of this volume.

[159] 'Zoonomia,' vol. i. p. 184.

[160] 'Zoonomia,' p. 171.

[161] 'Zoonomia,' p. 187.

[162] 'Nature,' March 14 and 21, 1878.

[163] See 'Botanic Garden,' part ii., note on Silene.

[164] 'On the Digestive Powers of Plants.' See Mr. Francis Darwin's lecture, already referred to.

[165] See 'Botanic Garden, part i., add. note, p. x.x.xix.

[166] Ibid., part ii., art. "Vallisneria."

[167] See 'Botanic Garden,' part i. cant 3, l. 440.

[168] 'Zoonomia,' vol. i. p. 107.

CHAPTER XIV.

FULLER QUOTATIONS FROM THE 'ZOONOMIA.'

The following are the pa.s.sages in the 'Zoonomia' which have the most important bearing on evolution:--

"The ingenious Dr. Hartley, in his work on man, and some other philosophers have been of opinion, that our immortal part acquires during this life certain habits of action or of sentiment which become for ever indissoluble, continuing after death in a future state of existence; and add that if these habits are of the malevolent kind, they must render their possessor miserable even in Heaven. I would apply this ingenious idea to the generation or production of the embryon or new animal, which partakes so much of the form and propensities of its parent.

"_Owing to the imperfection of language the offspring is termed a new animal, but is in truth a branch or elongation of the parent, since a part of the embryon-animal is, or was, a part of the parent, and therefore in strict language, cannot be said to be entirely new at the time of its production; and, therefore, it may retain some of the habits of the parent system._

"At the earliest period of its existence the embryon would seem to consist of a living filament with certain capabilities of irritation, sensation, volition, and a.s.sociation, and also with some acquired habits or propensities peculiar to the parents; the former of these are in common with other animals; the latter seem to distinguish or produce the kind of animal, whether man or quadruped, with the similarity of feature or form to the parent."[169]

Going on to describe the gradual development of the embryo, Dr. Darwin continues:--

"As the want of this oxygenation of the blood is perpetual (as appears from the incessant necessity of breathing by lungs or gills), the vessels become extended by the efforts of pain or desire to seek this necessary object of oxygenation, and to remove the disagreeable sensations which this want occasions."[170]

"The lateral production of plants by wires, while each new plant is thus chained to its parent, and continues to put forth another and another as the wire creeps onward on the ground, is exactly resembled by the tape-worm or taenia, so often found in the bowels, stretching itself in a chain quite from the stomach to the r.e.c.t.u.m. Linnaeus a.s.serts 'that it grows old at one extremity, while it continues to generate younger ones at the other, proceeding _ad infinitum_ like a sort of gra.s.s; the separate joints are called gourd worms, and propagate new joints like the parent without end, each joint being furnished with its proper mouth and organs of digestion.'"[171]

"Many ingenious philosophers have found so great difficulty in conceiving the manner of the reproduction of animals, that they have supposed all the numerous progeny to have existed in miniature in the animal originally created; and that these infinitely minute forms are only evolved or distended, as the embryon increases in the womb. This idea, besides its being unsupported by any a.n.a.logy we are acquainted with, ascribes a greater tenuity to organized matter than we can readily admit; as these included embryons are supposed each of them to consist of the various and complicate parts of animal bodies, they must possess a much greater degree of minuteness than that which was ascribed to the devils which tempted St. Anthony, of whom 20,000 were said to have been able to dance a saraband on the point of the finest needle without incommoding one another."[172]

"I conceive the primordium or rudiment of the embryon as secreted from the blood of the parent to consist of a simple living filament as a muscular fibre; which I suppose to be an extremity of a nerve of locomotion, as a fibre of the retina is an extremity of a nerve of sensation; as, for instance, one of the fibrils which compose the mouth of an absorbent vessel. I suppose this living filament of whatever form it may be, whether sphere, cube, or cylinder, to be endued with the capability of being excited into action by certain kinds of stimulus. By the stimulus of the surrounding fluid in which it is received from the male it may bend into a ring, and thus form the beginning of a tube.

Such moving filaments and such rings are described by those who have attended to microscopic animalculae. This living ring may now embrace or absorb a nutritive particle of the fluid in which it swims; and by drawing it into its pores, or joining it by compression to its extremities, may increase its own length or cra.s.situde, and by degrees the living ring may become a living tube.

"With this new organization, or accretion of parts, new kinds of irritability may commence; for so long as there was but one living organ it could only be supposed to possess irritability; since sensibility may be conceived to be an extension of the effect of irritability over the rest of the system. These new kinds of irritability and of sensibility in consequence of new organization appear from variety of facts in the more mature animals; thus ... the lungs must be previously formed before their exertions to obtain fresh air can exist; the throat, or oesophagus, must be formed previous to the sensation or appet.i.tes of hunger and thirst, one of which seems to reside at the upper end and the other at the lower end of that ca.n.a.l."[173]

It seems to me Dr. Darwin is wrong in supposing that the organ must have preceded the power to use it. The organ and its use--the desire to do and the power to do--have always gone hand in hand, the organism finding itself able to do more according as it advanced its desires, and desiring to do more simultaneously with any increase in power, so that neither appetency nor organism can claim precedence, but power and desire must be considered as Siamese twins begotten together, conceived together, born together, and inseparable always from each other. At the same time they are torn by mutual jealousy; each claims, with some vain show of reason, to have been the elder brother; each intrigues incessantly from the beginning to the end of time to prevent the other from outstripping him; each is in turn successful, but each is doomed to death with the extinction of the other.

"So inflamed tendons and membranes, and even bones, acquire new sensations; and the parts of mutilated animals, as of wounded snails and polypi and crabs, are reproduced; and at the same time acquire sensations adapted to their situation. Thus when the head of a snail is reproduced after decollation with a sharp razor, those curious telescopic eyes are also reproduced, and acquire their sensibility to light, as well as their adapted muscles for retraction on the approach of injury.

"With every change, therefore, of organic form or addition of organic parts, I suppose a new kind of irritability or of sensibility to be produced; such varieties of irritability or of sensibility exist in our adult state in the glands; every one of which is furnished with an irritability or a taste or appetency, and a consequent mode of action peculiar to itself.

"In this manner I conceive the vessels of the jaws to produce those of the teeth; those of the fingers to produce the nails; those of the skin to produce the hair; in the same manner as afterwards, about the age of p.u.b.erty, the beard and other great changes in the form of the body and disposition of the mind are produced in consequence of new developments; for, if the animal is deprived of these developments, those changes do not take place. These changes I believe to be formed not by elongation or distension of primeval stamina, but by apposition of parts; as the mature crab fish when deprived of a limb, in a certain s.p.a.ce of time, has power to regenerate it; and the tadpole puts forth its feet after its long exclusion from the sp.a.w.n, and the caterpillar in changing into a b.u.t.terfly acquires a new form with new powers, new sensations, and new desires."[174]

"From hence I conclude that with the acquisition of new parts, new sensations and new desires, as well as new powers are produced; and this by accretion to the old ones and not by distension of them. And finally, that the most essential parts of the system, as the brain for the purpose of distributing the powers of life, and the placenta for the purpose of oxygenating the blood, and the additional absorbent vessels, for the purpose of acquiring aliment, are first formed by the irritations above mentioned, and by the pleasurable sensations attending those irritations, and by the exertions in consequence of painful sensations similar to those of hunger and suffocation. After these an apparatus of limbs for future uses, or for the purpose of moving the body in its present natant state, and of lungs for future respiration, and of _testes_ for future reproduction, are formed by the irritations and sensations and consequent exertions of the parts previously existing, and to which the new parts are to be attached.[175]