Чарльз Дарвин
The Variation of Animals and Plants under Domestication — Volume 1
The actual weight of the main bones of the leg and wing in twelve breeds is given in the two first columns in Table 7.I. The calculated weight of the wing-bones relatively to the leg-bones, in comparison with the leg and wing-bones of G. bankiva, are given in the third column, — the weight of the wing-bones in G. bankiva being called a hundred. (7/73. It may be well to explain how the calculation has been made for the third column. In G. bankiva the leg-bones are to the wing-bones as 86: 54, or as (neglecting decimals) 100: 62; — in Cochins as 311: 162, or as 100: 52; — in Dorkings as 557: 248, or as 100: 44; and so on for the other breeds. We thus get the series of 62, 52, 44 for the relative weights of the wing-bones in G. bankiva, Cochins, Dorkings, etc. And now taking 100, instead of 62, for the weight of the wing-bones in G. bankiva, we get, by another rule of three, 83 as the weight of the wing-bones in Cochins; 70 in the Dorkings; and so on for the remainder of the third column in the table.)
TABLE 7.I. (Weights in grains.)
COLUMN 1. Actual Weight of Femur and Tibia.
COLUMN 2. Actual Weight of Humerus and Ulna.
COLUMN 3. Weight of Wing-bones relatively to the Leg-bones in comparison with these same bones in Gallus bankiva.
1. 2. 3.
Gallus bankiva — wild male 86 54 100
1. Cochin — male 311 162 83 2. Dorking — male 557 248 70 3. Spanish (Minorca) — male 386 183 75 4. Gold-Spangled Polish — male 306 145 75 5. Game, black-breasted — male 293 143 77 6. Malay — female 231 116 80 7. Sultan — male 189 94 79 8. Indian Frizzled — male 206 88 67 9. Burmese Jumper — female 53 36 108 10. Hamburgh (pencilled) — male 157 104 106 11. Hamburgh (pencilled) — female 114 77 108 12. Silk (black-boned) — female 88 57 103
In the eight first birds, belonging to distinct breeds, in this table, we see a decided reduction in the weight of the bones of the wing.
In the Indian Frizzled fowl, which cannot fly, the reduction is carried to the greatest extent, namely, to thirty-three per cent of their proper proportional weight. In the next four birds, including the Silk hen, which is incapable of flight, we see that the wings, relatively to the legs, are slightly increased in weight; but it should be observed that, if in these birds the legs had become from any cause reduced in weight, this would give the false appearance of the wings having increased in relative weight. Now a reduction of this nature has certainly occurred with the Burmese Jumper, in which the legs are abnormally short, and in the two Hamburghs and Silk fowl, the legs, though not short, are formed of remarkably thin and light bones. I make these statements, not judging by mere eyesight, but after having calculated the weights of the leg-bones relatively to those of G. bankiva, according to the only two standards of comparison which I could use, namely, the relative lengths of the head and sternum; for I do not know the weight of the body in G. bankiva, which would have been a better standard. According to these standards, the leg-bones in these four fowls are in a marked manner far lighter than in any other breed. It may therefore be concluded that in all cases in which the legs have not been through some unknown cause much reduced in weight, the wing-bones have become reduced in weight relatively to the leg-bones, in comparison with those of G. bankiva. And this reduction of weight may, I apprehend, safely be attributed to disuse.
To make Table 7.I. quite satisfactory, it ought to have been shown that in the eight first birds the leg-bones have not actually increased in weight out of due proportion with the rest of the body; this I cannot show, from not knowing, as already remarked, the weight of the wild Bankiva. (7/74. Mr. Blyth (in 'Annals and Mag. of Nat. Hist.' 2nd series volume 1 1848 page 456) gives 3 1/4 pounds as the weight of a full-grown male G. bankiva; but from what I have seen of the skins and skeletons of various breeds, I cannot believe that my two specimens of G. bankiva could have weighed so much.) I am indeed inclined to suspect that the leg-bones in the Dorking, No. 2 in the table, are proportionally too heavy; but this bird was a very large one, weighing 7 pounds 2 ounces, though very thin. Its leg-bones were more than ten times as heavy as those of the Burmese Jumper! I tried to ascertain the length both of the leg-bones and wing-bones relatively to other parts of the body and skeleton: but the whole organisation in these birds, which have been so long domesticated, has become so variable, that no certain conclusions could be reached. For instance, the legs of the above Dorking cock were nearly three-quarters of an inch too short relatively to the length of the sternum, and more than three-quarters of an inch too long relatively to the length of the skull, in comparison with these same parts in G. bankiva.
TABLE 7.II.
COLUMN 1. Length of Sternum (in inches and decimals.)
COLUMN 2. Depth of Crest of Sternum (in inches and decimals.).
COLUMN 3. Depth of Crest relatively to the length of the Sternum, in comparison with Gallus bankiva.
1. 2. 3.
Gallus bankiva — male. 4.20 1.40 100
1. Cochin — male. 5.83 1.55 78 2. Dorking — male. 6.95 1.97 84 3. Spanish — male. 6.10 1.83 90 4. Polish — male. 5.07 1.50 87 5. Game — male. 5.55 1.55 81 6. Malay — female. 5.10 1.50 87 7. Sultan — male. 4.47 1.36 90 8. Frizzled hen — male. 4.25 1.20 84 9. Burmese Jumper — female. 3.06 0.85 81 10. Hamburgh — male. 5.08 1.40 81 11. Hamburgh — female. 4.55 1.26 81 12. Silk fowl — female. 4.49 1.01 66
In Table 7.II. in the two first columns we see in inches and decimals the length of the sternum, and the extreme depth of its crest to which the pectoral muscles are attached. In the third column we have the calculated depth of the crest, relatively to the length of the sternum, in comparison with these same parts in G. bankiva. (7/75. The third column is calculated on the same principle as explained in footnote 7/73 above.)
By looking to the third column we see that in every case the depth of the crest relatively to the length of the sternum, in comparison with G. bankiva, is diminished, generally between 10 and 20 per cent. But the degree of reduction varies much, partly in consequence of the frequently deformed state of the sternum. In the Silk fowl, which cannot fly, the crest is 34 per cent less deep than what it ought to have been. This reduction of the crest in all the breeds probably accounts for the great variability, before referred to, in the curvature of the furculum, and in the shape of its sternal extremity. Medical men believe that the abnormal form of the spine so commonly observed in women of the higher ranks results from the attached muscles not being fully exercised. So it is with our domestic fowls, for they use their pectoral muscles but little, and, out of twenty-five sternums examined by me, three alone were perfectly symmetrical, ten were moderately crooked, and twelve were deformed to an extreme degree. Mr. Romanes, however, believes that the malformation is due to fowls whilst young resting their sternums on the sticks on which they roost.]
Finally, we may conclude with respect to the various breeds of the fowl, that the main bones of the wing have probably been shortened in a very slight degree; that they have certainly become lighter relatively to the leg-bones in all the breeds in which these latter bones are not unnaturally short or delicate; and that the crest of the sternum, to which the pectoral muscles are attached, has invariably become less prominent, the whole sternum being also extremely liable to deformity. These results we may attribute to the lessened use of the wings.
CORRELATION OF GROWTH.
I will here sum up the few facts which I have collected on this obscure, but important, subject. In Cochin and Game fowls there is perhaps some relation between the colour of the plumage and the darkness of the egg- shell. In Sultans the additional sickle-feathers in the tail are apparently related to the general redundancy of the plumage, as shown by the feathered legs, large crest, and beard. In two tailless fowls which I examined the oil-gland was aborted. A large crest of feathers, as Mr. Tegetmeier has remarked, seems always accompanied by a great diminution or almost entire absence of the comb. A large beard is similarly accompanied by diminished or absent wattles. These latter cases apparently come under the law of compensation or balancement of growth. A large beard beneath the lower jaw and a large top-knot on the skull often go together. The comb when of any peculiar shape, as with Horned, Spanish, and Hamburgh fowls, affects in a corresponding manner the underlying skull; and we have seen how wonderfully this is the case with Crested fowls when the crest is largely developed. With the protuberance of the frontal bones the shape of the internal surface of the skull and of the brain is greatly modified. The presence of a crest influences in some unknown way the development of the ascending branches of the premaxillary bone, and of the inner processes of the nasal bones; and likewise the shape of the external orifice of the nostrils. There is a plain and curious correlation between a crest of feathers and the imperfectly ossified condition of the skull. Not only does this hold good with nearly all crested fowls, but likewise with tufted ducks, and as Dr. Gunther informs me with tufted geese in Germany.
Lastly, the feathers composing the crest in male Polish fowls resemble hackles, and differ greatly in shape from those in the crest of the female. The neck, wing-coverts, and loins in the male bird are properly covered with hackles, and it would appear that feathers of this shape have spread by correlation to the head of the male. This little fact is interesting; because, though both sexes of some wild gallinaceous birds have their heads similarly ornamented, yet there is often a difference in the size and shape of feathers forming their crests. Furthermore, there is in some cases, as in the male Gold and in the male Amherst pheasants (P. pictus and amherstiae), a close relation in colour, as well as in structure, between the plumes on the head and on the loins. It would therefore appear that the same law has regulated the state of the feathers on the head and body, both with species living under natural conditions, and with birds which have varied under domestication.
CHAPTER 1.VIII
DUCK — GOOSE — PEACOCK — TURKEY — GUINEA-FOWL — CANARY-BIRD — GOLD-FISH — HIVE- BEES — SILK-MOTHS.
DUCKS, SEVERAL BREEDS OF. PROGRESS OF DOMESTICATION. ORIGIN OF FROM THE COMMON WILD-DUCK. DIFFERENCES IN THE DIFFERENT BREEDS. OSTEOLOGICAL DIFFERENCES. EFFECTS OF USE AND DISUSE ON THE LIMB-BONES.
GOOSE, ANCIENTLY DOMESTICATED. LITTLE VARIATION OF. SEBASTOPOL BREED.
PEACOCK, ORIGIN OF BLACK-SHOULDERED BREED.
TURKEY, BREEDS OF. CROSSED WITH THE UNITED STATES SPECIES. EFFECTS OF CLIMATE ON.
GUINEA-FOWL, CANARY-BIRD, GOLD-FISH, HIVE-BEES.
SILK-MOTHS, SPECIES AND BREEDS OF. ANCIENTLY DOMESTICATED. CARE IN THEIR SELECTION. DIFFERENCES IN THE DIFFERENT RACES. IN THE EGG, CATERPILLAR, AND COCOON STATES. INHERITANCE OF CHARACTERS. IMPERFECT WINGS. LOST INSTINCTS. CORRELATED CHARACTERS.
I will, as in previous cases, first briefly describe the chief domestic breeds of the duck: —
[BREED 1. COMMON DOMESTIC DUCK.
Varies much in colour and in proportions, and differs in instincts and disposition from the wild duck. There are several sub-breeds: —
1. The Aylesbury, of great size, white, with pale-yellow beak and legs; abdominal dermal sack largely developed.
2. The Rouen, of great size, coloured like the wild duck, with green or mottled beak; dermal sack largely developed.
3. Tufted Duck, with a large top-knot of fine downy feathers, supported on a fleshy mass, with the skull perforated beneath. The top-knot in a duck which I imported from Holland was two and a half inches in diameter.
4. Labrador (or Canadian, or Buenos Ayres, or East Indian); plumage entirely black; beak broader, relatively to its length, than in the wild duck; eggs slightly tinted with black. This sub-breed perhaps ought to be ranked as a breed; it includes two sub-varieties, one as large as the common domestic duck, which I have kept alive, and the other smaller and often capable of flight. (8/1. 'Poultry Chronicle' 1854 volume 2 page 91 and volume 1 page 330.) I presume it is this latter sub-variety which has been described in France (8/2. Dr. Turral 'Bull. Soc. d'Acclimat.' tome 7 1860 page 541.) as flying well, being rather wild, and when cooked having the flavour of the wild duck; nevertheless this sub-variety is polygamous, like other domesticated ducks and unlike the wild duck. These black Labrador ducks breed true; but a case is given by Dr. Turral of the French sub-variety producing young with some white feathers on the head and neck, and with an ochre-coloured patch on the breast.
BREED 2. HOOK-BILLED DUCK.
This bird presents an extraordinary appearance from the downward curvature of the beak. The head is often tufted. The common colour is white, but some are coloured like wild ducks. It is an ancient breed, having been noticed in 1676. (8/3. Willughby's 'Ornithology' by Ray page 381. This breed is also figured by Albin in 1734 in his 'Nat. Hist. of Birds' volume 2 page 86.) It shows its prolonged domestication by almost incessantly laying eggs, like the fowls which are called everlasting layers. (8/4. F. Cuvier in 'Annales du Museum' tome 9 page 128 says that moulting and incubation alone stops these ducks laying. Mr. B.P. Brent makes a similar remark in the 'Poultry Chronicle' 1855 volume 3 page 512.)
BREED 3. CALL DUCK.
Remarkable from its small size, and from the extraordinary loquacity of the female. Beak short. These birds are either white, or coloured like the wild duck.
BREED 4. PENGUIN DUCK.
This is the most remarkable of all the breeds, and seems to have originated in the Malayan archipelago. It walks with its body extremely erect, and with its thin neck stretched straight upwards. Beak rather short. Tail upturned, including only 18 feathers. Femur and metatarsus elongated.]
Almost all naturalists admit that the several breeds are descended from the common wild duck (Anas boschas); most fanciers, on the other hand, take as usual a very different view. (8/5. Rev. E.S. Dixon 'Ornamental and Domestic Poultry' 1848 page 117. Mr. B.P. Brent in 'Poultry Chronicle' volume 3 1855 page 512.) Unless we deny that domestication, prolonged during centuries, can affect even such unimportant characters as colour, size, and in a slight degree proportional dimensions and mental disposition, there is no reason whatever to doubt that the domestic duck is descended from the common wild species, for the one differs from the other in no important character. We have some historical evidence with respect to the period and progress of the domestication of the duck. It was unknown (8/6. Crawfurd on the 'Relation of Domesticated Animals to Civilisation' read before the Brit. Assoc. at Oxford 1860.) to the ancient Egyptians, to the Jews of the Old Testament, and to the Greeks of the Homeric period. About eighteen centuries ago Columella (8/7. Dureau de La Malle in 'Annales des Sciences Nat.' tome 17 page 164; and tome 21 page 55. Rev. E.S. Dixon 'Ornamental Poultry' page 118. Tame ducks were not known in Aristotle's time, as remarked by Volz in his 'Beitrage zur Kulturgeschichte' 1852 s. 78.) and Varro speak of the necessity of keeping ducks in netted enclosures like other wild fowl, so that at this period there was danger of their flying away. Moreover, the plan recommended by Columella to those who wish to increase their stock of ducks, namely, to collect the eggs of the wild bird and to place them under a hen, shows, as Mr. Dixon remarks, "that the duck had not at this time become a naturalised and prolific inmate of the Roman poultry-yard." The origin of the domestic duck from the wild species is recognised in nearly every language of Europe, as Aldrovandi long ago remarked, by the same name being applied to both. The wild duck has a wide range from the Himalayas to North America. It crosses readily with the domestic bird, and the crossed offspring are perfectly fertile.
Both in North America and Europe the wild duck has been found easy to tame and breed. In Sweden this experiment was carefully tried by Tiburtius; he succeeded in rearing wild ducks for three generations, but, though they were treated like common ducks, they did not vary even in a single feather. The young birds suffered from being allowed to swim about in cold water (8/8. I quote this account from 'Die Enten- und Schwanenzucht' Ulm 1828 s. 143. See Audubon 'Ornithological Biography' volume 3 page 168 on the taming of ducks on the Mississippi. For the same fact in England see Mr. Waterton in Loudon's 'Mag. of Nat. Hist.' volume 8 1835 page 542; and Mr. St. John 'Wild Sports and Nat. Hist. of the Highlands' 1846 page 129.), as is known to be the case, though the fact is a strange one, with the young of the common domestic duck. An accurate and well-known observer in England (8/9. Mr. E. Hewitt in 'Journal of Horticulture' 1862 page 773; and 1863 page 39.) has described in detail his often repeated and successful experiments in domesticating the wild duck. Young birds are easily reared from eggs hatched under a bantam; but to succeed it is indispensable not to place the eggs of both the wild and tame duck under the same hen, for in this case "the young wild ducks die off, leaving their more hardy brethren in undisturbed possession of their foster-mother's care. The difference of habit at the onset in the newly-hatched ducklings almost entails such a result to a certainty." The wild ducklings were from the first quite tame towards those who took care of them as long as they wore the same clothes, and likewise to the dogs and cats of the house. They would even snap with their beaks at the dogs, and drive them away from any spot which they coveted. But they were much alarmed at strange men and dogs. Differently from what occurred in Sweden, Mr. Hewitt found that his young birds always changed and deteriorated in character in the course of two or three generations; notwithstanding that great care was taken to prevent their crossing with tame ducks. After the third generation his birds lost the elegant carriage of the wild species, and began to acquire the gait of the common duck. They increased in size in each generation, and their legs became less fine. The white collar round the neck of the mallard became broader and less regular, and some of the longer primary wing-feathers became more or less white. When this occurred, Mr. Hewitt destroyed nearly the whole of his stock and procured fresh eggs from wild nests; so that he never bred the same family for more than five or six generations. His birds continued to pair together, and never became polygamous like the common domestic duck. I have given these details, because no other case, as far as I know, has been so carefully recorded by a competent observer of the progress of change in wild birds reared for several generations in a domestic condition.
From these considerations there can hardly be a doubt that the wild duck is the parent of the common domestic kind; nor need we look to other species for the parentage of the more distinct breeds, namely, Penguin, Call, Hook- billed, Tufted, and Labrador ducks. I will not repeat the arguments used in the previous chapters on the improbability of man having in ancient times domesticated several species since become unknown or extinct, though ducks are not readily exterminated in the wild state; — on some of the supposed parent-species having had abnormal characters in comparison with all the other species of the genus, as with Hook-billed and Penguin ducks; — on all the breeds, as far as is known being fertile together (8/10. I have met with several statements on the fertility of the several breeds when crossed. Mr. Yarrell assured me that Call and common ducks are perfectly fertile together. I crossed Hook-billed and common ducks, and a Penguin and Labrador, and the crossed Ducks were quite fertile, though they were not bred inter se, so that the experiment was not fully tried. Some half-bred Penguins and Labradors were again crossed with Penguins, and subsequently bred by me inter se, and they were extremely fertile.); — on all the breeds having the same general disposition, instinct, etc. But one fact bearing on this question may be noticed: in the great duck family, one species alone, namely, the male of A. boschas, has its four middle tail-feathers curled upwardly; now in every one of the above-named domestic breeds these curled feathers exist, and on the supposition that they are descended from distinct species, we must assume that man formerly hit upon species all of which had this now unique character. Moreover, sub-varieties of each breed are coloured almost exactly like the wild duck, as I have seen with the largest and smallest breeds, namely Rouens and Call ducks, and, as Mr. Brent states (8/11. 'Poultry Chronicle' 1855 volume 3 page 512.), is the case with Hook-billed ducks. This gentleman, as he informs me, crossed a white Aylesbury drake and a black Labrador duck, and some of the ducklings as they grew up assumed the plumage of the wild duck.
With respect to Penguins, I have not seen many specimens, and none were coloured precisely like the wild duck; but Sir James Brooke sent me three skins from Lombok and Bali, in the Malayan archipelago; the two females were paler and more rufous than the wild duck, and the drake differed in having the whole under and upper surface (excepting the neck, tail-coverts, tail, and wings) silver-grey, finely pencilled with dark lines, closely like certain parts of the plumage of the wild mallard. But I found this drake to be identical in every feather with a variety of the common breed procured from a farm-yard in Kent, and I have occasionally elsewhere seen similar specimens. The occurrence of a duck bred under so peculiar a climate as that of the Malayan archipelago, where the wild species does not exist, with exactly the same plumage as may occasionally be seen in our farm-yards, is a fact worth notice. Nevertheless the climate of the Malayan archipelago apparently tends to cause the duck to vary much, for Zollinger (8/12. 'Journal of the Indian Archipelago' volume 5 page 334.), speaking of the Penguin breed, says that in Lombok "there is an unusual and very wonderful variety of ducks." One Penguin drake which I kept alive differed from those of which the skins were sent me from Lombok, in having its breast and back partially coloured with chestnut-brown, thus more closely resembling the Mallard.
From these several facts, more especially from the drakes of all the breeds having curled tail-feathers, and from certain sub-varieties in each breed occasionally resembling in general plumage the wild duck, we may conclude with confidence that all the breeds are descended from A. boschas.
[I will now notice some of the peculiarities characteristic of the several breeds. The eggs vary in colour; some common ducks laying pale-greenish and others quite white eggs. The eggs which are first laid during each season by the black Labrador duck, are tinted black, as if rubbed with ink. A good observer assured me that one year his ducks of this breed laid almost perfectly white eggs. Another curious case shows what singular variations sometimes occur and are inherited; Mr. Hansell (8/13. 'The Zoologist' volumes 7, 8 1849-1850 page 2353.) relates that he had a common duck which always laid eggs with the yolk of a dark-brown colour like melted glue; and the young ducks, hatched from these eggs, laid the same kind of eggs, so that the breed had to be destroyed.
(FIGURE 39. SKULLS, viewed laterally, reduced to two-thirds of the natural size. A. Wild Duck. B. Hook-billed Duck.)
The Hook-billed duck is highly remarkable (see figure 39, of skull); and its peculiar beak has been inherited at least since the year 1676. This structure is evidently analogous with that described in the Bagadotten carrier pigeon. Mr. Brent (8/14. 'Poultry Chronicle' 1855 volume 3 page 512.) says that, when Hook-billed ducks are crossed with common ducks, "many young ones are produced with the upper mandible shorter than the lower, which not unfrequently causes the death of the bird." With ducks a tuft of feathers on the head is by no means a rare occurrence; namely, in the True-tufted breed, the Hook-billed, the common farm-yard kind, and in a duck having no other peculiarity which was sent to me from the Malayan archipelago. The tuft is only so far interesting as it affects the skull, which is thus rendered slightly more globular, and is perforated by numerous apertures. Call ducks are remarkable from their extraordinary loquacity: the drake only hisses like common drakes; nevertheless, when paired with the common duck, he transmits to his female offspring a strong quacking tendency. This loquacity seems at first a surprising character to have been acquired under domestication. But the voice varies in the different breeds; Mr. Brent (8/15. 'Poultry Chronicle' volume 3 1855 page 312. With respect to Rouens see ditto volume 1 1854 page 167.) says that Hook-billed ducks are very loquacious, and that Rouens utter a "dull, loud, and monotonous cry, easily distinguishable by an experienced ear." As the loquacity of the Call duck is highly serviceable, these birds being used in decoys, this quality may have been increased by selection. For instance, Colonel Hawker says, if young wild ducks cannot be got for a decoy, "by way of make-shift, SELECT tame birds which are the most clamorous, even if their colour should not be like that of wild ones." (8/16. Col. Hawker 'Instructions to young Sportsmen' quoted by Mr. Dixon in his 'Ornamental Poultry' page 125.) It has been erroneously asserted that Call ducks hatch their eggs in less time than common ducks. (8/17. 'Cottage Gardener' April 9, 1861.)
The Penguin duck is the most remarkable of all the breeds; the thin neck and body are carried erect; the wings are small; the tail is upturned; and the thigh-bones and metatarsi are considerably lengthened in proportion with the same bones in the wild duck. In five specimens examined by me there were only eighteen tail-feathers instead of twenty as in the wild duck; but I have also found only eighteen and nineteen tail-feathers in two Labrador ducks. On the middle toe, in three specimens, there were twenty- seven or twenty-eight scutellae, whereas in two wild ducks there were thirty-one and thirty-two. The Penguin when crossed transmits with much power its peculiar form of body and gait to its offspring; this was manifest with some hybrids raised in the Zoological Gardens between one of these birds and the Egyptian goose (Anser aegyptiacus) (8/18. These hybrids have been described by M. Selys-Longchamps in the 'Bulletins (tome 12 № 10) Acad. Roy. de Bruxelles.'), and likewise with some mongrels which I raised between the Penguin and Labrador duck. I am not much surprised that some writers should maintain that this breed must be descended from an unknown and distinct species; but from the reasons already assigned, it seems to me far more probable that it is the descendant, much modified by domestication under an unnatural climate, of Anas boschas.
OSTEOLOGICAL CHARACTERS.
The skulls of the several breeds differ from each other and from the skull of the wild duck in very little except in the proportional length and curvature of the premaxillaries. These latter bones in the Call duck are short, and a line drawn from their extremities to the summit of the skull is nearly straight, instead of being concave as in the common duck; so that the skull resembles that of a small goose. In the Hook-billed duck (figure 39), these same bones as well as the lower jaw curve downwards in a most remarkable manner, as represented. In the Labrador duck the premaxillaries are rather broader than in the wild duck; and in two skulls of this breed the vertical ridges on each side of the supra-occipital bone are very prominent. In the Penguin the premaxillaries are relatively shorter than in the wild duck; and the inferior points of the paramastoids more prominent. In a Dutch tufted duck, the skull under the enormous tuft was slightly more globular and was perforated by two large apertures; in this skull the lachrymal bones were produced much further backwards, so as to have a different shape and nearly to touch the post. lat. processes of the frontal bones, thus almost completing the bony orbit of the eye. As the quadrate and pterygoid bones are of such complex shape and stand in relation with so many other bones, I carefully compared them in all the principal breeds; but excepting in size they presented no difference.
(FIGURE 40. — CERVICAL VERTEBRA, of natural size. A. Eighth cervical vertebra of Wild Duck viewed on haemal surface. B. Eighth cervical vertebra of Call Duck, viewed as above. C. Twelfth cervical vertebra of Wild Duck viewed laterally. D. Twelfth cervical vertebra of Aylesbury Duck, viewed laterally.)
VERTEBRAE AND RIBS.
In one skeleton of the Labrador duck there were the usual fifteen cervical vertebrae and the usual nine dorsal vertebrae bearing ribs; in the other skeleton there were fifteen cervical and ten dorsal vertebrae with ribs; nor, as far as could be judged, was this owing merely to a rib having been developed on the first lumbar vertebra; for in both skeletons the lumbar vertebrae agreed perfectly in number, shape, and size with those of the wild duck. In two skeletons of the Call duck there were fifteen cervical and nine dorsal vertebrae; in a third skeleton small ribs were attached to the so-called fifteenth cervical vertebra, making ten pairs of ribs; but these ten ribs do not correspond, or arise from the same vertebra, with the ten in the above-mentioned Labrador duck. In the Call duck, which had small ribs attached to the fifteenth cervical vertebra, the haemal spines of the thirteenth and fourteenth (cervical) and of the seventeenth (dorsal) vertebrae corresponded with the spines on the fourteenth, fifteenth, and eighteenth vertebrae of the wild duck: so that each of these vertebrae had acquired a structure proper to one posterior to it in position. In the eighth cervical vertebra of this same Call duck (figure 40, B), the two branches of the haemal spine stand much closer together than in the wild duck (A), and the descending haemal processes are much shortened. In the Penguin duck the neck from its thinness and erectness falsely appears (as ascertained by measurement) to be much elongated, but the cervical and dorsal vertebrae present no difference; the posterior dorsal vertebrae, however, are more completely anchylosed to the pelvis than in the wild duck. The Aylesbury duck has fifteen cervical and ten dorsal vertebrae furnished with ribs, but the same number of lumbar, sacral, and caudal vertebrae, as far as could be traced, as in the wild duck. The cervical vertebrae in this same duck (figure 40, D) were much broader and thicker relatively to their length than in the wild (C); so much so, that I have thought it worth while to give a sketch of the twelfth cervical vertebra in these two birds. From the foregoing statements we see that the fifteenth cervical vertebra occasionally becomes modified into a dorsal vertebra, and when this occurs all the adjoining vertebrae are modified. We also see that an additional dorsal vertebra bearing a rib is occasionally developed, the number of the cervical and lumbar vertebrae apparently remaining the same as usual.
