Genus

“ And this certainly is the case, if varieties be looked at as incipient species; for my tables clearly show as a general rule that, wherever many species of a genus have been formed, the species of that genus present a number of varieties, that is of incipient species, beyond the average. It is not that all large genera are now varying much, and are thus increasing in the number of their species, or that no small genera are now varying and increasing ”

“ The type of a genus is that species upon the characters of which the genus was originally framed and named, 134and theoretically, however generic groups may be subsequently divided to suit views or to meet systems, the primitive generic type is assumed to retain the primitive generic name. It is much to be doubted whether, in every case, the type is the true pattern, or leader, or centre of the group called the genus; nor is it likely if genera be natural groups. ”

“ I have said a large genus, because we have seen in the second chapter, that on an average more of the species of large genera vary than of small genera; and the varying species of the large genera present a greater number of varieties. We have, also, seen that the species, which are the commonest and the most widely-diffused, vary more than rare species with restricted ranges. ”

“ It is a truly wonderful fact — the wonder of which we are apt to overlook from familiarity — that all animals and all plants throughout all time and space should be related to each other in groups, subordinate to groups, in the manner which we everywhere behold — namely, varieties of the same species most closely related, species of the same genus less closely and unequally related, forming sections and sub-genera, species of distinct genera much less closely related, and genera related in different degrees, forming sub-families, families, orders, sub-classes, and classes. ”

“ If we take a genus having a score of species, recent and extinct, and destroy four-fifths of them, no one doubts that the remainder will stand much more distinct from each other. If the extreme forms in the genus happen to have been thus destroyed, the genus itself will stand more distinct from other allied genera. ”

“ A Genus comprehends one or more species, so essentially different in formation, nature, and often many adventitious qualities, from other plants, as to constitute a distinct family or kind, no less permanent, and founded in the immutable laws of the creation, than the different species of such a genus. ”

“ Specific differences divide genus into species.According then, to the differences which produce another thing do the divisions of genera into species arise, and the definitions arising from genus and such differences are assigned. On the other hand, as to those which only make a thing different in quality, diversities alone consist, and the changes of subsistence of a thing ”

“ After this glance at the variations peculiar to each species, a more important consideration presents itself, that of the change of the species themselves; that ancient and immemorial degeneration made in each family, or in every genus, under which we may comprehend the proximating species. Among all terrestrial animals there are only a few detached species, which, like the human, at once compose both species and genus. ”

“ The type-species of every genus, the type-genus of every family, is then, one which possesses all the characters and properties of the genus in a marked and prominent manner. The type of the Rose family has alternate stipulate leaves, wants the albumen, has the ovules not erect, has the stigmata simple, and besides these features, which distinguish it from the exceptions or varieties of its class, it has the features which make it prominent in its class. ”

“ The definition of the genus is simply a statement of the plan of structure which is common to all the species included under that genus; just as the definition of the species is a statement of the common plan of structure which runs throughout the individuals which compose the species. ”

“ We see here illustrated in all but the final stage that process by which a solitary widely-ranging species, alone representing its genus, becomes ultimately in each group the parent of a number of peculiar species. The polymorphous, or extremely variable, species plays in this period the all-important part. ”

“ For genus and difference co-subvert species, so that these are prior to species. They are also more known, for if species is known, it is necessary that genus also and difference should be known, (as he who knows man, knows both animal and pedestrian,) but when genus or difference is known, it is not necessary that species also should be known, wherefore species is more unknown. ”

“ We know that individuals which are mere varieties of the same species would, if their pedigree could be traced back far enough, terminate in a single stock; so, according to the train of reasoning before described, the species of a genus, and even the genera of a great family, must have had a common point of departure. ”

“ A Kind which is not divisible into other Kinds, cannot be a genus, because it has no species under it; but it is itself a species, both with reference to the individuals below and to the genera above, (Species Prædicabilis and Species Subjicibilis.) But every Kind which admits of division into real Kinds (as animal into quadruped, bird, &c., or quadruped into various species of quadrupeds) is a genus to all below it, a species to all genera in which it is itself included. ”

“ 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. ”

“ As greater numbers of species have become known the earlier genera have undergone subdivision until in the modern systems almost any structural character not subject to intergradation and capable of exact definition is held to distinguish a genus. As the views of these characters are undergoing constant change, and as different writers look upon them from different points of view, or with different ideas of convenience, we have constant changes in the boundaries of genera. ”

“ We can only retain the genus as an artificial one, along with many other such, till the science be arrived at a greater degree of perfection; keeping, the mean time, naturaI orders in view as the grand object of our systematic inquiries, and cherishing every truly natural genus as a fixed point, on which we may found the principles of future discoveries. ”

“ We must observe too the genus of the assigned genus, and so always the superior genus, whether all things are predicated of the species, and whether they are so in reply to what a thing is, for all superior genera must be predicated of species, in respect to what a thing is ”

“ All the phenomena presented by the species of a genus are reproduced by the genera of a family, and often in a more marked degree. Owing, however, to the extreme restriction of genera by modern naturalists, there are not many among the higher animals that have a world-wide distribution. ”

“ On the other hand, a genus consisting of numerous species ranging over an entire region or the greater part of one, is a dominant group, which has most likely been for some time extending its range, and whose origin dates back to a remote period. ”

“ Naturalists give to every genus a name, and also a name to each species in the genus. Since we naturalists want to know what butterflies or other species of animals and plants are found in other countries, and to be sure that we all (whatever our native language may be) mean the same thing by a name, Latin names are given to the genera and the species, and are necessarily used when one wishes to be sure that one is understood. ”

“ Looking to the large number of species to be taken into account, convenience has demanded what science would withhold, and the genera established by the ornithologists of a preceding generation have been broken up by their successors into multitudinous sections—the more adventurous making from 150 to 180 of such groups, the modest being content with 120 or thereabouts, but the last dignifying each of them by the title of genus. ”

“ The genus Homo may fall into several species; so that what some call the varieties of a single species are really different species of a single genus. 8. The varieties of mankind may be too great [51] to be included in even a genus. There may be two or even more genera to an order. 9. Many of the present varieties may represent the intermixtures of species no longer extant in a pure state. 10. All known varieties may be referable to a single species; but there may be new species undescribed. 11. All existing varieties may be referable to a single species ”

“ but this alone would never account for so habitual and large an amount of difference as that between varieties of the same species and species of the same genus. ”

“ Variety comes in upon occasion. For, although a species may have no recognized varieties, a genus implies at least one species belonging to it; every genus is of some order, and every order of some class.
533. But these grades by no means exhaust the resources of classification, nor suffice for the elucidation of all the distinctions which botanists recognize. In the first place, a higher grade than that of class is needful for the most comprehensive of divisions, that of all plants into the two Series of Phanerogamous and Cryptogamous (6) ”

“ Though we can not indicate the distinctive properties of the Kind, we may indicate its nearest natural affinities, by incorporating into its name the name of the proximate natural group of which it is one of the species. On this principle is founded the admirable binary nomenclature of botany and zoology. In this nomenclature the name of every species consists of the name of the genus, or natural group next above it, with a word added to distinguish the particular species. ”

“ A closer scrutiny of the facts, however, makes the term hybridism less isolated and more vague. The words species and genus, and still more subspecies and variety, do not correspond with clearly marked and sharply defined zoological categories, and no exact line can be drawn between the various kinds of crossings from those between individuals apparently identical to those belonging to genera universally recognized as distinct. ”

“ This gradual increase in number of the species of a group is strictly conformable with the theory; for the species of the same genus, and the genera of the same family, can increase only slowly and progressively ”

“ To what extent these hints for the discrimination of species will be found to avail in practice, it is difficult to say, but it seems desirable that they should speedily be brought to the test of experience, since there is no genus, of the same extent, in which it is so difficult to determine the species. ”

“ The chief one is that species differ in usually several characters one from another and in large genera there is often a bewildering recombination of characters of the genus in the species belonging to it. Species and varieties are concepts of convenience, nay of absolute necessity, in talking or writing about plants, but hardly expressions of exact truth. ”

“ If the genealogical tree is truly represented by the natural system, it would seem that for each genus a single ancestral form must be postulated, for each group of genera a single more primitive form, and so in general for each of the higher classificatory categories, right up to the phylum. Species of one genus must be descended from a generic ancestral form, genera of one family from a single family Urform, and so on for the higher categories. ”

“ To make the denotation of zoological names precise, exact workers are endeavouring to associate the conception of types with names, a process which can be made simple and definite with new work, but which presents great difficulties in the attempt to apply it to existing terms. Every family should have designated one of its genera as the type genus, every genus a type species and so forth. In the case of species or sub-species the type is a single specimen, either the only one before the author when writing his description, or one definitely selected by him, the others being paratypes. ”

“ 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? ”

“ So far as my own observations go, and they have not been few, if I have read the great book of nature aright, the genera, instead of being reduced, might with propriety be multiplied without the risk of our being burthened with a genus for every species, as some writers affect to fear would then be the case. ”