Thomas Vernon Wollaston

“ In selecting the examples which we have lately discussed, I have avoided as much as possible those startling instances of variation which distant quarters of the globe will readily supply, because there are vast numbers of our naturalists who will not acknowledge the validity of any evidence which would tend to amalgamate, in a broad sense, the species of the Old and New Worlds. I have therefore contented myself with such data as must fall within our common experience, feeling satisfied that if the principle be allowed in the one case, it cannot long be objected to in the other. ”

“ A fact many times repeated, and which comes within our daily experience, is too often [Pg 20] looked upon as a matter of course, and as therefore beneath the notice of an intelligent mind; yet the man who regards truth as valuable, for its own sake, under whatever aspect it may come, and who can rise to the appreciation of results, whether they be of rare or constant occurrence, will have learnt to pronounce nothing as unimportant which may supply a single link in that chain of knowledge which would be broken and imperfect without it. ”

“ I propose rather to consider some of the ordinary effects of isolation, as mere matters of experience; and to allow geology to tell its own tale when we come to examine the problem of self-dispersion, as occasionally interrupted by subsidence.
If we except a few of the Heteromera and apterous Curculionidæ, which appear to be influenced in a different manner, the power of isolation over insect form is perhaps more especially to be detected in a deterioration of stature. ”

“ Yet a practised eye can detect discrepancies innumerable in specimens which appear absolutely alike to one that is uneducated; whilst a third person, better qualified still, will trace out other and more delicate distinctions, with even greater precision. And thus it is that we rise, step by step, even amongst the humbler representatives of the animal kingdom, to the comprehension of that great truth which is so conspicuous in the nobler ones, and which we have already summoned to our aid, that "there is no similitude in Nature which owneth not also to a difference." ”

“ To be aware that these barriers exist, and yet to feel surprised, especially in a country where the species are principally wingless, that we do not discover indications of a general uniformity in its fauna, involves an absurdity,—unless the doctrine of specific centres of creation be a mere coinage of the brain. ”

“ Such a doctrine is in reality nothing more than the transmutation theory, in all its unvarnished fulness; and I do not see how it can be for a moment maintained, so long as facts (and not reasoning only) are to be the basis of our speculations. I repeat, that it is merely within fixed specific bounds that I would advocate a freedom of development, in obedience to influences from without: only I would widen those limits to a much greater extent than has been ordinarily done,—so as to let in the controlling principle of physical agents, as a significant adjunct for our contemplation. ”

“ Before we proceed to inquire to what extent the outward aspect of insects is liable to be controlled by the physical state of the areas in which they severally obtain, it may not be altogether out of place to offer a few reflections on the superiority which some regions possess intrinsically over others, both for the increase and diffusion of the animal tribes. To suppose that all countries within the same parallels of latitude are equally favourable for the development of life (not to mention the after-dispersion of it) , is contrary to experience ”

“ The mind, moreover, having been chained and fettered for a season to the mere detail of facts, breaks forth, under such circumstances, with all the vigour with which the contemplation of truth has gifted it, and takes its flight as it were to a clearer sky ”

“ To trace out the progressive development of animal life, from its humblest phases; and to mark, as they become visible in the intermediate grades, the first rudiments of organs and instincts which are destined to attain their maximum in the higher ones, embody but a small portion of what it is the naturalist's mission to investigate. ”

“ Like the ever-shifting curves which the white foam of the untiring tide describes upon the shore, races may ebb and flow; but they have their boundaries, in either direction, beyond which they can never pass. And thus in every species we may detect, to a greater or less extent, the emblem of instability and permanence combined: although perceived, when inquired into, to be fickle and fluctuating in their component parts, in their general outline they remain steadfast and unaltered, as of old ”

“ Such questions as these, however, though they may occasionally perplex the tyro, or amateur, are not likely to be raised by anyone who has mastered the merest alphabet of zoology,—and who is aware that the integrity of Nature is something real and positive, as experience indeed is ever tending more and more to corroborate, and by no means the day-dream of an enthusiastic, or fertile, imagination. ”

“ It must be recollected however that, in the instances to which we would draw attention, small aberrations are all that can be usually looked for, since climate of itself does not appear to be very potent in its action. We should remember, also, that the boundaries of insect instability are restricted; and, although we would advocate freedom of development within limits which are more or less comprehensive according to the species, to pass beyond them would be confusion, and such as could result from a lapsus Naturæ only, rather than from a power of legitimate variation. ”

“ The fact of aberration, to which we would briefly allude in this chapter, requires but little comment; it is patent à priori. As a matter of experience, every observer who has spent a week in the field of Nature [Pg 8] knows it to exist. However difficult it may be, in some instances, to distinguish aright between species and varieties, as rigidly defined, there is an instinct within us which often recognizes the latter, even at first sight, as unmistakeably such: and in these cases, a well-educated eye, although of course occasionally deceived, will not often be found to err. ”

“ But even this, although I believe it to contain much presumptive truth, will not altogether suffice to account for the phænomena which we see; for Ireland is not only remarkable for the paucity of its species, but also for the paucity of its individuals,—and the latter fact cannot be explained by any stretch of the migration-hypothesis. We are compelled therefore to conclude, that Ireland, like the other countries to which we have already alluded, presents conditions (altogether irrespective of latitude) which must be regarded as adverse to the general prosperity of the insect races. ”

“ Moreover, there is a curious tendency which I have remarked in most islands, that the wings (especially the metathoracic ones) of their insect inhabitants are liable to be retarded in their development,—often indeed to such an extent as to become actually evanescent: and I believe it to be a law of Nature, that when any particular organ is either stunted or taken away, the creature receives a compensation for its loss either by the undue enlargement of some other one [36] , or else in a general increase of its bulk. ”

“ We must remember, however, that, where certainty is not to be had, probability must be accepted in its stead; or, as an old writer has well expressed it: "That we ought to follow probability when certainty leaves us, is plain,—because it then becomes the only light and guide that we have. For, unless it is better to wander and fluctuate in absolute uncertainty than to follow such a guide; unless it be reasonable to put out our candle because we have not the light of the sun, it must be reasonable to direct our steps by probability, when we have nothing clearer to walk by". ”

“ So that the migratory birds generally, which pass to and fro between Europe and Africa in that particular latitude, would appear to form separate races from those which traverse the ocean to our own country; and to be, most of them, remarkable, inter alia, for a slight shortening of their organs of transit.
If, however, the members of the insect tribes are capable of but small variation in actual structure, with the exception, in certain instances, of the greater or less development of the wings; we shall find that their external characters are much more prone to instability. ”

“ The discovery, at all times, of what we feel to be actually certain is in itself so fascinating, that the very data which it gives us are scarcely more prized than the mere knowledge that we have gained a single additional light to guide us on our forward way: for, since in the inductive sciences we can but climb from step to step, at a slow and even pace, we hail with inward satisfaction whatsoever may tend to lighten our task, and to lead us more quickly onwards (gradually though we must of necessity advance) towards its final accomplishment. ”

“ We know that there are certain species of an alpine and boreal character, which cannot live except in a climate of low temperature,—guaranteed to them either by elevation in one land, or by a higher latitude in another: and let us picture the consequences of the gradual sinking of a mountain chain, even to a small extent, the summits of which only just afforded the conditions of atmosphere necessary for the continuance of creatures like these. ”

“ I believe that, if analogies were more carefully studied in the lower departments of the animal kingdom, we should be less inclined to deny some sort of uniformity to the action of elements and conditions which, by a law of Nature, must at times operate equally upon the various and dissimilar members of the organic creation. Amongst the Insecta, where the individuals exist in such multitudes that accuracy in generalizations concerning them, becomes, as it were, peculiarly within our reach, this doctrine cannot be too rigidly insisted upon ”

“ The geologist who would interpret the grand phænomena of the earth's crust apart from statical and dynamical knowledge, and without the help which the chemist, mineralogist, anatomist, zoologist, and botanist can afford him, stands a fair chance of leaving his problems unsolved; whilst the students of zoology and botany who would endeavour to understand, and account for, what they see in the animal and vegetable worlds around them, without calling in geology to their aid, must assuredly be prepared to fail signally in their attempts. ”

“ Luxuriance of vegetation and sheltered districts are alike conducive, in the Annulosa, to the development both of the body and its adornment; or, in other words, where the vegetable creation attains its maximum (which it certainly does not do in situations which are exposed to the irritating consequences of a perpetually stormy atmosphere) , there the animal world will be usually observed to thrive.
There are many insects which appear to have two distinct states, both in magnitude and hue, which we are seldom (in some instances, I believe, never) able to unite by intermediate links, or grades ”

“ The time for such a step is yet far off: perhaps indeed, considering the innovations of nomenclature which it would necessitate, it will never arrive at all; yet the fact remains the same, that, if analogy with creatures of a more perfect development be not altogether disallowed us, during our researches into the insect tribes, or if similar causes may be presumed to have somewhat similar effects in opposite sections of the [Pg 15] animate world, an enlargement of our prescribed limits, for specific variation, ought in reality to follow (sooner or later) as an inevitable consequence. ”

“ A moderate degree of heat, and that only during a certain portion of the year, may suffice in quiescent regions to keep up the equilibrium of the organic world, the various members of which, whether animals or plants, are ensured, in such countries, their alternate seasons of activity and rest; but within the tropics, life, in all its aspects, is ever vigorous; and, though the several species may have their appointed times of partial repose, there is no such thing as tranquillity for the mass. ”

“ Few observers can have failed to remark, that increased [Pg 35] altitude frequently corresponds, both in its fauna and flora, to a higher latitude; and that, consequently, if we ascend the mountains of a southern land, we shall be struck, at times, by the presence of a host of species which obtain at a lower level in more temperate zones. This is peculiarly traceable in the Madeira Islands,—which, from their subaustral position, and height (the loftiest peak of the central mass exceeding 6000 feet above the sea) , afford a rich field to the student of zoological geography. ”

“ To imagine that when an insect has become much altered in its general contour, all the parts of which it is composed are equally affected, is contrary to experience; since observation warns us that there are but few actual members which are capable of change,—whilst even the external features, or secondary diagnostics, are only interfered with according to a fixed law, the workings of which are necessarily modified, in proportion as the constitutions of the several animals are differently organized and acted upon. ”

“ As regards that most obscure of questions, what the limits of species really are, observation alone can decide the point. It frequently happens indeed that even observation itself is insufficient to render the lines of demarcation intelligible,—therefore, how much more mere dialectics! ”

“ Nevertheless, we may briefly repeat, that, so far as the first is concerned, it is in islands that we detect the maximum of instability to which the wings of the Insecta are liable, and that it is in seasons of extraordinary heat that their development [Pg 99] is everywhere inclined (if at all) to be especially stimulated: whilst, as regards the second, it will be sufficient to state, that in continents, when any decided alteration takes place in the organs of flight, it for the most part comes to pass that an increased (rather than diminished) action is the result ”

“ It usually happens that those species which have the greatest pliability of organization, those which are most capable of accommodating themselves to a great variety of new circumstances, are most serviceable to man. ”

“ Now we have already shown, that where the gradual lowering of a region has taken place, there will be, of necessity, an [Pg 116] undue accumulation of life on its loftiest pinnacles,—for, even allowing a certain number of species (which even formerly were only just able to find a sufficient altitude for their development) to have perished, we shall have concentrated at that single elevation the residue of all those which have survived from the ancient elevations above it. ”