« iepriekšējāTurpināt »
Why, then, hesitate to acknowledge two species of sheep; the race of one permanently covered with hair, and that of the other as permanently covered with wool?-especially if (as has been shown) the difference between these integuments is not merely one of color and marking, (as in the cases of the horse and the ass, and the horse and the ass and the zebra,) but where the shape, direction, and inclination of the pile are different; where the disposition of the coloring matter is remarkably different; and, above all, where the number, shape, position, and mode of adherence of the scales of the cortex are so entirely different as to render the one altogether unfit for felting and fulling, and not liable to shrink; while the other is admirably adapted to felting and fulling, and liable to shrink. Take all these things into consideration, and then say whether there is not, at least, as much ground for believing these two animals to constitute two species as there exists in regard to the unity or plurality of the humps of the camel, or of the horns of the rhinoceros. And then, again, remember that, to establish this modification, there must be a difference of organization-a difference in the functions which the apparatus of each kind have, respectively, to perform: for instance, the fibres and cortex of the wool, while they subserve all the ordinary purposes which they do in hair, are also the medium of conveyance for the coloring matter of the former integument; while that of the latter flows in a central canal. "Species of plants (says Mills) are not only real kinds, but are, probably, all of them, real lowest kinds, or inferior species." And he adds, "I say probably, (not certainly,) because this is not the consideration by which the botanist determines what shall or shall not be admitted as a species; but which, consistently with experience, might have been produced from the same stock. So that in the present instance, (seeing that the same law prevails in the animal commonwealth,) where the inquiry is "whether the hairy sheep and the woolly sheep are not two distinct species ?"-we are not bound to show absolutely that they are descended from different parentage, but only that, consistently with experience, they might have been descended from different parentages. And after having shown the difference between hair and wool, and having pointed out the character of the discrepancies upon which zoologists have been in the habit of erecting species, we would confidently inquire whether any naturalist, who had presented to him two newly-discovered wild animals, otherwise alike, but one of which always produced wool and the other one hair, would hesitate to consign. them to two specific departments? And if he would not, then why, in the case now before us, should we allow habit, born in ignorance and nurtured in stubbornness, to prevail over the dictates of reason and experience?
Let it not be supposed, from what has been hitherto said, that too little attention has been paid to the laws of physiology; for we do not believe that the zoological and physiological, and even the embryological, meanings of the word species materially differ. The author last cited remarks "that it seems to be a law of physiology that animals and plants do really, in the physiological as well as in the popular sense, propagate their kind, transmitting to their descendants all the distinction of kind (down
*By the adoption of this rule no inconsistency is introduced, for (as this learned author shaws) this distinction, in most (and probably in all) cases, happily accords with the other.
to the most special and lowest kind) which they themselves possess." Now surely one of the distinctions of kind of the hairy sheep is to produce hair, and one of the distinctions of kind of the woolly sheep "is to produce wool." In like manner Agassiz, (in Prin. of Zool., p. 43,) says: "The constancy of species is a phenomenon depending on immaterial nature. Animals (and plants also) produce their kind generation after generation. We shall hereafter show that all animals may be traced back, in the embryo, to a mere point upon the yolk of the egg, bearing no resemblance whatever to the future animal. But even here,' he adds, "an immaterial principle, which no external influence can prevent or modify, is present and determines its future form; so that the egg of the hen can produce nothing but the chicken, and the egg of the codfish can produce only the cod. It may therefore be said, with truth, that the chicken and the cod existed in the egg before their formation." Now although this learned author has given us examples drawn from two classes of animals, viz: the chicken and the fish, it is fair to presume that he also meant his observation to apply to animals of different species, but of the same class and order; and therefore that the hair of the hairy sheep, and the wool of the woolly sheep, according to his notion, depend upon an immaterial principle, which no external influence can prevent or modify. The question of species is therefore one of fact, and Dr. Morton was right when he said "all circumstances which tend to establish analogies are proper and necessary for the determination." We admit, when common parentage can be traced with certainty, that it constitutes the best evidence which the nature of the case allows; but he who would reject secondary evidence, when primary cannot be obtained, would place himself in the position of one who would shut his eyes to all other light, because he cannot always bask in the rays of the noonday sun. Between animals of the same species nature throws no impediment whatever to free sexual intercourse, and the progeny form a permanent selfsupporting race of animals, which inherit equally the properties of both parents. But with animals of different species, there is a natural abhorence to amalgamate, which sometimes cannot be overcome at all, and with others exhibits itself in various ways and in various degrees; and the progeny are always incapable of securing a permanent and self-supporting race, in the proper sense of those terms. This is a most valuable rule for the determination of species, when properly understood and correctly applied; but, from inattention and inadvertence, it has been converted into a fruitful hot-bed of error, as will be hereafter shown in the proper place.
The common cow and the buffalo have a natural antipathy to each other; such is the fixed aversion formed between these creatures (as we are informed by Goldsmith) that the cow refuses to feed with the buffalo, which she nearly resembles. Wild asses (as we are told by the same beautiful author) live in herds, but they will not allow a horse to come among them; if, perchance, one strays into the boundary of their gra zing ground, they fall upon him without giving him time to retreat; they kick and bite him until he is left exhausted on the spot. The babyroussa, or East India hog, is often seen with the wild boar, with which, however, he is never known to engender; and the peccary of South America, although he herds will the wild hog, which he so much resembles, has never been known to breed with him. This is the voice of nature,
proclaiming, in unmistakable terms, her abhorence of the amalgamation of species.
How is it when man exerts the powerful influence of domestication? Sometimes even here all efforts to subvert nature are abortive. Buffon, for three years, kept a male water-dog and a she-wolf together, but they refused to have any intercourse. Goldsmith tells us that a similar experiment was tried with a fox and a dog; and the hare and the rabbit, though so nearly resembling each other in form and disposition, refuse to hold any communication. Buffon bred up several of both kinds together; but, from being at first indifferent, they soon became enemies, and they would sometimes combat until one was disabled or destroyed. How is it, it may be asked, with the horse and the ass? The mule, it is asserted, may be engendered by mixing either a horse and a she-ass or a jack and a mare. When the latter method, which is the one proposed, is resorted to, a horse is used as a teaser, and before the jack is brought forward the mare is hoodwinked. Is this the free sexual intercourse spoken of in the rule above quoted? But we have another question to ask in regard to this connexion, viz: Is the mule prolific? Is it capable of continuing the race? Goldsmith says, "that, from the great resemblance between the horse and the ass, one would be led to suppose that they are of the same species-that the ass was only a degenerate horse; but that they are perfectly distinct-an inseparable line having been drawn between them." He adds, "that it had been said by Aristotle that the male mule was prolific; but that, after two thousand years' experience, this assertion had been modified; that others had said that in warm climates female mules are prolific; but that, upon examining the cases, it was found that such progeny were incapable of continuing the race.
Fortunately, we have the reports of two cases which occurred in our own country; which, as they are exceedingly interesting, we will be excused for giving at large:
"John Thomson Kilby, of Springhill, Nansemond county, Virginia, was the owner of a female mule, which, on the 23d of April, 1834, was delivered of a male young one. She was not suspected of being with foal, and therefore it was not known what animal was the father; but suspicion alighted upon a three-year-old colt belonging to Mr. Kilby, which had been allowed to run with the mules on Sundays; also, the young one resembled the colt. When born it was very lean; but its mother (although she had a small udder) having plenty of milk, it throve pretty well until the 20th of October in the same year, when (having been previously weaned) it was taken sick, and died of lockjaw the following day. Another (female) young one was born of the same mule, on the same plantation, on the 13th of August, 1835, and died on the 26th of August, 1836, after having been sick two or three days only. It was in fine order; ran with its mother, which was doing nothing, in good pasture. When taken sick it had every medical attention paid to it; but it was found impossible to effect a passage through it; and, upon a post mortem examination, all the food and medicine were found in the stomach, none having ever passed into the intestines." We recollect how, at the time, these two births were dwelt upon as
* He died 322 years before Christ.
proving the mule to be prolific; ut we ask the intelligent reader whether they do not fall far short of the mark? They exhibit no ground to believe that such progeny can ever be the foundation of a permanent self-supporting race; which, as we have seen, is one of the conditions of the rule above quoted.
We will next refer to some cases of intercourse, or supposed intercourse, between the goat and the sheep, premising that, although the evidence in these cases is somewhat contradictory, yet its weight will lead us to a similar result. Smith (in Hist. of Man, p. 117,) says that "goats and sheep intermix, producing permanently fertile hybrids." But Bellchambers, in a note to Goldsmith's Nat. Hist. of Man, &c., p. 245, qualifies the above broad assertion as follows: "The sheep and the goat propagate. The buck goat is found to produce, with the ewe, an animal which, in two or three generations, returns to the sheep, and seems to retain no marks of its ancient progenitor." How the breeding goes on during these "two or three generations," we are not informed, but we take it for granted that the progeny are bred towards the sheep. Surely, no one would pretend, from this evidence, to aver that such hybrids were permanently fertile, much less that they constitute a self-supporting race. Now, let us see what the author of Illustra tions of Nat. Hist., p. 151, with all these remarks before him, has to say upon the subject:
"Although the goat is a distinct species, and, possibly, further removed from the sheep than the horse is from the ass, yet the buck will propagate with the ewe. But although these intercourses happen very frequently, and are sometimes prolific, yet no intermediate species has ever been found between them." "No new or middle race has
It seems, then, that all that we know with certainty is, that the goat and the sheep, in their domestic state, frequently have intercourse, and not that they have free intercourse, as exist between members of the same species; that this intercourse is sometimes" (not uniformly) prolific, and that here the propagation, per se, ends. If you desire to continue the progeny, you must call in the aid of some one belonging to the original parents. And even this breeding is somewhat doubtful; for one of our correspondents, viz: Mr. Samuel Patterson, of Patterson's Mills, Washington county, Pennsylvania, in a letter to us upon this subject, says: "I have made inquiry, but have heard of no case of intercourse between the sheep and the goat being prolific. I have tried the experiment to some extent, myself, with the goat and the ewe, but without production. I have never seen the ram having intercourse with the she goat, although I have had them running together at tupping time. Mr. Plummer, a neighbor of mine, has made the experiment more fully than I have, but with the same result. I am perfectly satisfied that the fine woolled sheep (the woolly sheep) and the goat will not mix. I know of no case where it has been tried with the coarse hairy sheep." From all that has been said, we feel warranted in believing that the best rule we possess of discriminating between species is, to inquire whether nature has thrown any impediment between the animals to free sexual intercourse, and whether the progeny form a permanent, self-supporting race of animals, which inherit equally the properties of both parents. And we feel confident that a trial of the hairy sheep and the woolly sheep by
this law, in order to ascertain whether they are one and the same, or two distinct species, will result entirely in favor of the ground we havetaken. Mr. Youatt, when speaking of the attempt in England to amalgamate the South Down sheep (which is itself a hybrid, being a mixture of the hairy and the woolly species) with the Leicester sheep,(which belongs to the hairy species,) pronounces it a failure; and he adds that the promised advantages to be derived from the South Down with the merinos WERE DELUSIVE. (See Essay upon Sheep, p. 233.) It is true that this author does not appear to be aware of the cause of this failure-one of the reasons why the expectations to which he has referred were delusive; but he has furnished us with the facts, and the inferences to be adduced from them, which are irresistible. Dr. Robert Knox, an English lecturer on anatomy, and corresponding member of the Natural Academy of Medicine in France, in a recent work upon the races of men, p. 52, says: "The theories put forth, from time to time, of the production of a new variety, permanent and self-supporting, independent of any drafts or supplies from the pure breeds, have been distinctly dispoved. It holds neither in sheep nor cattle." And again, on page 68: "But the statement in question is not even true of sheep; for by no effort, saving that of constant, never-ceasing intermixture, or draft on the pure breeds, can a mixed breed be maintained."
So Colonel Randall (in Sheep Husbandry in the South, p. 170) admits, that any attempt to unite the merinos and the Leicester by crosses is an unqualified absurdity. It is true that this last gentleman (incautiously, as we presume) advises the crossing of the South Down and the merino; but such a crossing of a hybrid, formed from an amalgamation of the two species with the pure race of one of the species, is no less an "unqualified absurdity;" although the reason may not at first be quite so apparent to every one. We have not only the pleasure to hope,but the vanity to antici pate, that Col. Randall, after further reflection upon this important question, will agree with us in opinion. If he does not, we would like to hear from himself why the crossing of the South Down and the merino merits his recommendation, while the mixture of the merino and the Leicester is so inconsistent with reason and common sense. Having satisfied ourselves that the hairy sheep and the woolly sheep are members of two species, the next step in the inquiry is, What is the consequence of their amalgamation? Will it promote or mar the great object of the American sheep-breeder? Considering the very great extent to which sheep are now raised in the United States, and the general prevalence of crossing,.. these are important questions. The grand desideratum of the American sheep-breeder is, to form and preserve either one permanent and self-supporting race of animals-which shall inherit equally the good qualities of both parents, which shall produce, with the least trouble and expense, either the greatest quantity of the finest quality of fine, soft, and strong wool, which will felt and full in the greatest perfection, or the greatest quantity of the finest quality of fine, strong, and soft fleece, that will not shrink or two races, one answering to either of these requirements. Now, to perform either or both of these, he must, in each flock, confine himself to one species; for as often as the parents are of different species, the offspring will be hybrids; none of which possess the power of permanently fixing and self supporting a race such as has been mentioned. Among all animals, intelligent and instinctive, there exists a natural abhorrence