Species

“ From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, 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 comparison with mere individual differences, is also applied arbitrarily, for convenience sake. ”

“ From the time of Linnaeus to the commencement of the present century, it seemed a sufficient definition of the term species to say that "a species consisted of individuals all resembling each other, and reproducing their like by generation." ”

“ If we pass up into the kingdoms of the living, and study plants and animals, the same unity of phenomena meets us. Our classification terms—order, genus, species, and so forth—are as artificial as our names for the geological systems. No one holds to-day that any single species is clearly marked off from all others. ”

“ Is it satisfactorily proved, in fact, that species may be originated by selection? that there is such a thing as natural selection? that none of the phenomena exhibited by species are inconsistent with the origin of species in this way? ”

“ When we look to the individuals of the same variety or sub-variety of our older cultivated plants and animals, one of the first points which strikes us, is, that they generally differ much more from each other, than do the individuals of any one species or variety in a state of nature. ”

“ We use the term species, to designate a number of individual plants, which, in all essential and unvarying characters, resemble each other more closely than they do any other plant; the term genus or kind, to designate an assemblage of nearly allied species, agreeing with one another in general structure and appearance more closely than they do with any other species. ”

“ Species is in the animal kingdom that which copulates without necessity and compulsion. The same definition is applicable to plants. The species range, without doubt, according to the diversities in the individual organs themselves, which admit of a great multitude of combinations, the number of which is not as yet to be determined. ”

“ The meaning attached to the term species, in natural history, is very simple and obvious. It includes only one circumstance—namely, an original distinctness and constant transmission of any character. A race of animals, or plants, marked by any peculiarities of structure which have always been constant and undeviating, constitutes a species. ”

“ Throughout this volume, we have felt considerable inconvenience, from the adopted dogmatical classification of plants, and have all along been floundering between species and variety, which certainly under culture soften into each other. A particular conformity, each after its own kind, when in a state of nature, termed species, no doubt exists to a considerable degree. ”

“ On the ordinary view of each species having been independently created, why should specific characters, or those by which the species of the same genus differ from each other, be more variable than the generic characters in which they all agree? ”

“ If we now look upon the definition of a species, as given by a gentleman foremost in the ranks as a describer of species, we find it formulated as follows: A species represents "a primary established law, stamped with a persistent form (a type) pertaining solely to itself, with the power of successively reproducing the same form, and none other;" ”

“ Once we have gained the fundamental conceptions as to what is meant by a "species," we are able intelligently to consider innumerable facts of the most diverse kind as to their peculiar structure and colours, their number, localities, their interaction and dependence on other living things, their modifications for special modes of life, their isolation or their ubiquity. ”

“ However bare and simple this definition of species may appear to be, we confidently appeal to all practical naturalists, whether zoologists, botanists, or palaeontologists, to say if, in the vast majority of cases, they know, or mean to affirm anything more of the group of animals or plants they so denominate than what has just been stated. Even the most decided advocates of the received doctrines respecting species admit this. ”

“ But, besides the fortunes of individual plants and animals, there is another class of questions, of great interest, but of great difficulty;—the fortunes of each species. In what manner do species which were not, begin to be? as geology teaches us that they many times have done; and, as even our own reasonings convince us they must have done, at least in the case of the species among which we live. ”

“ The differentia, therefore, of a species may be defined to be, that part of the connotation of the specific name, whether ordinary or special and technical, which distinguishes the species in question from all other species of the genus to which on the particular occasion we are referring it. ”

“ Natural conditions do not permit of the existence of too many species or sub-species. But it is clear that there are types, call them genera, species, or what you will, that have, by virtue of some inherent fitness and flexibility of adaptation, survived and mastered other types. ”

“ In a former discussion, I have asked for facts which show, aside from the theory, that any one species of animal, distinctly marked as a continuing type, is connected by intermediate types or forms with any pre-existing race of another character. ”

“ Reasoning from analogy and from the different varieties of the same species, and the different species under one genus, among all other animals, he pointed out their different modes of living, and the different designs of the Creator, that appeared to be evinced with respect to them. ”

“ Hence it is the most flourishing, or, as they may be called, the dominant species,— those which range widely, are the most diffused in their own country, and are the most numerous in individuals,— which oftenest produce well-marked varieties, or, as I consider them, incipient species. ”

“ How much of the acclimatisation of species to any peculiar climate is due to mere habit, and how much to the natural selection of varieties having different innate constitutions, and how much to both means combined, is an obscure question. ”

“ It may be safely assumed that our readers have a general conception of the nature of the objects to which the word "species" is applied; but it has, perhaps, occurred to few, even of those who are naturalists ex professo, to reflect, that, as commonly employed, the term has a double sense and denotes two very different orders of relations. When we call a group of animals, or of plants, a species, we may imply thereby either, that all these animals or plants have some common peculiarity of form or structure ”

“ The continual development of species by the formation of new varieties here produces a mass of intermediate forms which connect the so-called “good” species, which efface their boundaries, and render their sharp specific distinction completely illusory. ”

“ And we can clearly understand these analogies, if species have once existed as varieties, and have thus originated: whereas, these analogies are utterly inexplicable if each species has been independently created. ”

“ That this does habitually happen, we must infer from most of the innumerable species throughout nature presenting well-marked differences; whereas varieties, the supposed prototypes and parents of future well-marked species, present slight and ill-defined differences. ”

“ The concrete sciences, Zoology and Botany, confine themselves to species which really exist, or can be shown to have really existed: and do not concern themselves with the mode in which even these would comport themselves under all circumstances, but only under those which really take place. ”

“ From the above considerations, it appears that species have a real existence in nature; and that each was endowed, at the time of its creation, with the attributes and organization by which it is now distinguished. ”

“ The forms which possess in some considerable degree the character of species, but which 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 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. ”

“ Let us see how far above principles of variation apply to wild animals. Wild animals vary exceedingly little—yet they are known as individuals{47}. British Plants, in many genera number quite uncertain of varieties and species: in shells chiefly external conditions{48}. ”

“ How can we deal with such a large subject in a brief way? It seems best to confine our attention in this chapter to an attempt to answer the question, What is a species? and are "species" natural groups clearly delimited by nature? ”

“ We must here remark at once, without going further into the definition of species, that all zoologists and botanists in their classificatory systems, in the practical distinction and designation of species of animals and plants, never troubled, or even could trouble, themselves in the slightest degree about this assumed creation of the parent forms. ”

“ But further light may be thrown on the subject, by a careful analysis of the facts which can be collected relative to the nature and origination of varieties; and it may be satisfactory to my readers to survey this field of enquiry.”
Granting, then, the truth of the limitation of species to be established, and taking as the definition of species the power of continual propagation, we have it proved at the commencement of the work, that “all human races are of one species;” ”

“ I have discussed this subject of analogous variation at considerable length, because, in a future work on natural species, it will be shown that the varieties of one species frequently mock distinct species—a fact in perfect harmony with the foregoing cases, and explicable only on the theory of descent. ”

“ As the species of the same genus usually have, though by no means invariably, much similarity in habits and constitution, and always in structure, the struggle will generally be more severe between them, if they come into competition with each other, than between the species of distinct genera. ”

“ It seems, then, that the prime question resolves itself into whether each species as a whole has something inherent which prompts it to vary irrespective of its environments, or whether a correlation can be established between the variation of species and certain physical conditions inducing these variations, and here let me add that of all groups of animals from species through genera to higher divisions, that group of individuals recognized as a species has the most tangible existence. ”

“ Causes of Variability — Effects of Habit and the use or disuse of Parts — Correlated Variation — Inheritance — Character of Domestic Varieties — Difficulty of distinguishing between Varieties and Species — Origin of Domestic Varieties from one or more Species — Domestic Pigeons, their Differences and Origin — Principles of Selection, anciently followed, their Effects — Methodical and Unconscious Selection — Unknown Origin of our Domestic Productions — Circumstances favourable to Man's power of Selection. ”