Ichthyology

“ Recognized by experts of foreign countries with one accord as the most eminent living authority on economic ichthyology, America owes to his fostering care and unwearied labor the existence of a whole generation of ichthyologists, breeders of fishes, and inventors of appliances of all sorts for use in connection with the taking, preservation, and increase of these animals. ”

“ Among the invertebrate tribes the propagation of the species is, in the vast majority of cases, a mere mechanical function, like that of feeding or respiration, and the eggs once deposited, the parent has no further care of her young. But among the vertebrated animals, on the other hand, the perpetuation of the race forms the central pillar round which the natural affections are entwined. It parcels out every species into pairs, in each of which the mates are bound together by the strongest ties of attachment. ”

“ The zoological works of Fleming, Jenyns, Yarrell, Bell, and W. Thompson, have enumerated the species and treated of the distribution of our indigenous animals, those of Smith, Hooker, Lindley, Babington, Henslow, and especially Watson, have done the same service for our native flora; but the history of the formation, if I may so say, of that fauna and flora, remains to be investigated. This essay is offered as a contribution towards such a history.
There are three modes in which an isolated area may become peopled by animals and plants. ”

“ As the zoölogist divides the vertebrate animals into mammals, birds, reptiles, amphibians, and fishes, so the anthropologist divides the generic North American Indian culture into the cultures of these ten areas. The naturalist however cannot stop with a group as inclusive as the mammals, and goes on to subdivide them into orders, such as the rodents, carnivores, ungulates, and the like. Each of these again he goes on splitting into families, genera, and finally species. The species correspond to the smallest groups in human society, namely the tribes or nations. ”

“ These species once lived geographically separate, but contemporaneously; and they and their specific peculiarities have perished, to rise again in our domestic races. These races breed together with unqualified fertility. In the form of skull and horns they recall one or other of the extinct species; but collectively they constitute a new main species. That from their various breeds, the three or any one of the aboriginal species would ever emerge in a state of pristine purity, would be an utterly ludicrous assertion. ”

“ The study of the mixture of human races in this region has also occupied me much, and I have procured numerous photographs of all the types which I have been able to observe. The principal result at which I have arrived is, that the races bear themselves towards each other as do distinct species; that is to say, that the hybrids, which spring from the crossing of men of different races, are always a mixture of the two primitive types, and never the simple reproduction of the characters of one or the other progenitor, as is the case among the races of domestic animals. ”

“ The reasons for concluding that the several principal races have not descended from so many aboriginal and unknown stocks may be grouped under the following six heads:—Firstly, if the eleven chief races have not arisen from the variation of some one species, together with its geographical races, they must be descended from several extremely distinct aboriginal species; for no amount of crossing between only six or seven wild forms could produce races so distinct as pouters, carriers, runts, fantails, turbits, short-faced tumblers, jacobins, and trumpeters. ”

“ It is difficult, even in contemplation, to anticipate the time when we shall be entitled to make any other hypothesis in regard to all the marine tribes, and to by far the greater number of the terrestrial;—such as birds, which possess such unlimited powers of migration; insects, which, besides the variability of each species in number, are also so capable of being diffused to vast distances; and cryptogamous plants, to which, as to many other classes, both of the animal and vegetable kingdom, similar observations are applicable. ”

“ Whether it be large animals that eat down the stem—as goats prevent the extension of pines—or birds that devour the fruit, or insects that attack some vital organ, or vegetable parasites that disorganize the tissues, the chances are great that in a new region the species will not find the enemies that have been adapted to check its extension in its native home. Of the marvellous complexity of the agencies that interact in the life-history of each species we first formed some estimate through the teachings of Darwin ”

“ Darwin and Dr. Hooker reply, that when animals or plants migrate into new countries, whether assisted by man, or without his aid, the most successful colonisers appertain by no means to those types which are most allied to the old indigenous species. On the contrary, it more frequently happens that members of genera, orders, or even classes, distinct and foreign to the invaded country, make their way most rapidly, and become dominant at the expense of the endemic species. ”

“ This development has been closely associated with the growth of biometric methods applied to zoology and botany.
One of the important facts that has been recognized by a study of the morphology of the races is that man must be considered as a domesticated animal, and that even those tribes which are industrially the most primitive are somewhat removed from the anatomical conditions characterizing the wild animals. It appears, however, that the degree of domestication has strongly increased with the growing complexity of industrial organization ”

“ The doctrine of the origin of our several domestic races from several aboriginal stocks, has been carried to an absurd extreme by some authors. They believe that every race which breeds true, let the distinctive characters be ever so slight, has had its wild prototype. At this rate there must have existed at least a score of species of wild cattle, as many sheep, and several goats in Europe alone, and several even within Great Britain. One author believes that there formerly existed in Great Britain eleven wild species of sheep peculiar to it! ”

“ A wild ass, though brought up from its birth in a stable, would make a very intractable costermonger's moke. We may infer from this that the first subjugation of each of our common domestic animals was the achievement of some genius, or of some tribe favourably situated, and that they spread from that centre by sale or barter, rather than that they were separately domesticated in many places. This would partly explain why a few species of widely different families are so universally kept in all countries to the exclusion of hundreds of species nearly allied and apparently as suitable. ”

“ Two different cultivated races, or wild varieties of one species, are said in all cases to possess the power of producing bastards which can fruitfully mix with one another, or with one of their parent forms, and thus propagate themselves; on the other hand, two really different species, two cultivated or wild species of one genus, are said never to be able to produce from one another bastards which can be fruitfully crossed with one another, or with one of their parent species. ”

“ We know that insects and plants are so transported. Birds and ocean-currents carry seeds from land to land. Insects on a blade of grass or a fallen bough are carried down a river by the current to found colonies of their race far from their place of origin. And such circumstances give rise to races and varieties among species modifiable by the peculiarities of their new localities. The accidental migrations of man may be considered as belonging to the epoch of culture-migration, since they must more usually have occurred with a race advanced in the art of navigation. ”

“ The fecundity of the smaller, murine species, is great, and from time to time they increase inordinately in favorable places, and swarm abroad in vast and destructive migrations. Were it not for the fact that the rodents furnish the principal part of the food of predatory mammals, reptiles, and birds, and are thus kept down, the globe would soon become so populous with this tribe that hardly anything else could maintain existence. ”

“ The determination of the indigenous and derived species of a formation or larger division is of the utmost importance, as it enables us to retrace the steps by which the formation has reached its present structure, and to reconstruct formations long since disappeared. To render it less difficult, it is necessary to scrutinize the derived elements closely, first, because it is easiest to recognize the indigenous species by eliminating the derived, and second, because this analysis will show that not all derived species have entered the formation at the same time and from the same sources. ”

“ These characters are no less permanent and constant in the different species of the human family than in those of any other family in the animal kingdom, and my observations upon the cross-breeds in South America have convinced me that the varieties arising from contact between these human species, or so-called races, differ from true species just as cross-breeds among animals differ from true species, and that they retain the same liability to revert to the original stock as is observed among all so-called varieties or breeds. ”

“ In the varied forms and functions they present, as beasts of prey, as grazers or root diggers, as ground-running, tree-climbing, burrowing or cave-haunting forms, some solitary and slow, others agile and gregarious, the marsupial tribe in its isolated corner of the earth exhibits an epitome of the whole mammalian world. It shows in a conspicuous way how the necessity and habit of making a living in [Pg 281] varied circumstances, and exposed to lively competition, restricting every species to a particular manner, brings about a suitable modification of structure. ”

“ I would also plead the poverty of our British Fauna in the sub-class, and my almost entire ignorance of exotic Phalænæ. Even supposing myself acquainted with all our indigenous species, they will barely furnish a systematist with a clew to the truth: you may pick up a single link of a chain, yet fail to discover the length of that chain, or the situation in that chain which the link originally possessed. ”

“ But the differences between them are such as obtain between allied species generally. Large genera are composed, in great part, of such species; and it is interesting to show how the great and beautiful diversity within a large genus is brought about by the working of laws within our comprehension.
A few remarks on the way races are produced will be here in place. Naturalists have been generally inclined to attribute the formation of local varieties or races of a species to the direct action of physical conditions on individuals belonging to it which have migrated into new localities. ”

“ Engelmann and I have been noting the species truly indigenous here which, becoming ruderal or campestral, are increasing in the number of individuals instead of diminishing as the country becomes more settled and forests removed. The list of our wild plants which have become true weeds is larger than I had supposed, and these have probably all of them increased their geographical range—at least, have multiplied in numbers in the Northern States since settlements. ”

“ It is evident that in this "dark continent," where the influences which make for human advancement have been so slight, we have the best field for the selection of species that may hereafter be brought to the use of man. There is evidently danger, in the advance in the civilizing process, that the native forms which, owing to their fitness to the physical conditions of the country, might be made useful to its people, may be utterly destroyed by hunters. ”

“ In form, colour, sculpture, &c., they vary infinitely in different tribes; some of them we have already described and figured, and it will be more satisfactory to notice the peculiarities of others in connection with the particular history of the insects that produce them, than to introduce here a lengthened general account of objects so dissimilar.
The number of eggs laid by different species, is as various as their properties. At one extremity of the scale they approach the vertebrated races, at the other they surpass all other animals in the creation. ”

“ Having alluded to the subject of reversion, I may here refer to a statement often made by naturalists— namely, that our domestic varieties, when run wild, gradually but certainly revert in character to their aboriginal stocks. Hence it has been argued that no deductions can be drawn from domestic races to species in a state of nature. ”

“ On these same principles, we can understand, as I have endeavoured to show, why oceanic islands should have few inhabitants, but of these a great number should be endemic or peculiar; and why, in relation to the means of migration, one group of beings, even within the same class, should have all its species endemic, and another group should have all its species common to other quarters of the world. ”

“ We have already shown that there is a large amount of local variation in a considerable number of species, and we may be sure that were it not for the constant intermingling and intercrossing of the individuals inhabiting adjacent localities this tendency to local variation in adaptation to slightly different conditions, would soon form distinct races. But as soon as the area is divided into two portions the intercrossing is stopped, and the usual result is that two closely allied races, classed as representative species, become formed. ”