DOMESTIC RABBITS.
DOMESTIC RABBITS DESCENDED FROM THE COMMON WILD RABBIT.
ANCIENT DOMESTICATION.
ANCIENT SELECTION.
LARGE LOP-EARED RABBITS.
VARIOUS BREEDS.
FLUCTUATING CHARACTERS.
ORIGIN OF THE HIMALAYAN BREED.
CURIOUS CASE OF INHERITANCE.
FERAL RABBITS IN JAMAICA AND THE FALKLAND ISLANDS.
PORTO SANTO FERAL RABBITS.
OSTEOLOGICAL CHARACTERS.
SKULL.
SKULL OF HALF-LOP RABBITS.
VARIATIONS IN THE SKULL ANALOGOUS TO DIFFERENCES IN DIFFERENT SPECIES OF
HARES.
VERTEBRAE.
STERNUM.
SCAPULA.
EFFECTS OF USE AND DISUSE ON THE PROPORTIONS OF THE LIMBS AND BODY.
CAPACITY OF THE SKULL AND REDUCED SIZE OF THE BRAIN.
SUMMARY ON THE MODIFICATIONS OF DOMESTICATED RABBITS.
All naturalists, with, as far as I know, a single exception, believe that
the several domestic breeds of the rabbit are descended from the common
wild species; I shall therefore describe them more carefully than in the
previous cases. Professor Gervais (4/1. M.P. Gervais 'Hist. Nat. des
Mammiferes' 1854. tome 1 page 288.) states "that the true wild rabbit is
smaller than the domestic; its proportions are not absolutely the same; its
tail is smaller; its ears are shorter and more thickly clothed with hair;
and these characters, without speaking of colour, are so many indications
opposed to the opinion which unites these animals under the same specific
denomination." Few naturalists will agree with this author that such slight
differences are sufficient to separate as distinct species the wild and
domestic rabbit. How extraordinary it would be, if close confinement,
perfect tameness, unnatural food, and careful breeding, all prolonged
during many generations, had not produced at least some effect! The tame
rabbit has been domesticated from an ancient period. Confucius ranges
rabbits among animals worthy to be sacrificed to the gods, and, as he
prescribes their multiplication, they were probably at this early period
domesticated in China. They are mentioned by several of the classical
writers. In 1631 Gervaise Markham writes, "You shall not, as in other
cattell, looke to their shape, but to their richnesse, onely elect your
buckes, the largest and goodliest conies you can get; and for the richnesse
of the skin, that is accounted the richest which hath the equallest mixture
of blacke and white haire together, yet the blacke rather shadowing the
white; the furre should be thicke, deepe, smooth, and shining;...they are
of body much fatter and larger, and, when another skin is worth two or
three pence, they are worth two shillings." From this full description we
see that silver-grey rabbits existed in England at this period; and what is
far more important, we see that the breeding or selection of rabbits was
then carefully attended to. Aldrovandi, in 1637, describes, on the
authority of several old writers (as Scaliger, in 1557), rabbits of various
colours, some "like a hare," and he adds that P. Valerianus (who died a
very old man in 1558) saw at Verona rabbits four times bigger than ours.
(4/2. U. Aldrovandi 'De Quadrupedibus digitatis' 1637 page 383. For
Confucius and G. Markham see a writer who has studied the subject in
'Cottage Gardener' January 22, 1861 page 250.)
From the fact of the rabbit having been domesticated at an ancient period,
we must look to the northern hemisphere of the Old World, and to the warmer
temperate regions alone, for the aboriginal parent-form; for the rabbit
cannot live without protection in countries as cold as Sweden, and, though
it has run wild in the tropical island of Jamaica, it has never greatly
multiplied there. It now exists, and has long existed, in the warmer
temperate parts of Europe, for fossil remains have been found in several
countries. (4/3. Owen 'British Fossil Mammals' page 212.) The domestic
rabbit readily becomes feral in these same countries, and when variously
coloured kinds are turned out they generally revert to the ordinary grey
colour. (4/4. Bechstein 'Naturgesch. Deutschlands' 1801 b. 1 page 1133. I
have received similar accounts with respect to England and Scotland.) Wild
rabbits, if taken young, can be domesticated, though the process is
generally very troublesome. (4/5. 'Pigeons and Rabbits' by E.S. Delamer
1854 page 133. Sir J. Sebright 'Observations on Instinct' 1836 page 10)
speaks most strongly on the difficulty. But this difficulty is not
invariable, as I have received two accounts of perfect success in taming
and breeding from the wild rabbit. See also Dr. P. Broca in 'Journal de la
Physiologie' tome 2 page 368.) The various domestic races are often
crossed, and are believed to be quite fertile together, and a perfect
gradation can be shown to exist from the largest domestic kinds, having
enormously developed ears, to the common wild kind. The parent-form must
have been a burrowing animal, a habit not common, as far as I can discover,
to any other species in the large genus Lepus. Only one wild species is
known with certainty to exist in Europe; but the rabbit (if it be a true
rabbit) from Mount Sinai, and likewise that from Algeria, present slight
differences; and these forms have been considered by some authors as
specifically distinct. (4/6. Gervais 'Hist. Nat. des Mammiferes' tome 1
page 292.) But such slight differences would aid us little in explaining
the more considerable differences characteristic of the several domestic
races. If the latter are the descendants of two or more closely allied
species, these, with the exception of the common rabbit, have been
exterminated in a wild state; and this is very improbable, seeing with what
pertinacity this animal holds its ground. From these several reasons we may
infer with safety that all the domestic breeds are the descendants of the
common wild species. But from what we hear of the marvellous success in
France in rearing hybrids between the hare and rabbit (4/7. See Dr. P.
Broca's interesting memoir on this subject in Brown-Sequard 'Journ. de.
Phys.' volume 2 page 367.), it is possible, though not probable, from the
great difficulty in making the first cross, that some of the larger races,
which are coloured like the hare, may have been modified by crosses with
this animal. Nevertheless, the chief differences in the skeletons of the
several domestic breeds cannot, as we shall presently see, have been
derived from a cross with the hare.
There are many breeds which transmit their characters more or less truly.
Every one has seen the enormous lop-eared rabbits exhibited at our shows;
various allied sub-breeds are reared on the Continent, such as the so-
called Andalusian, which is said to have a large head with a round
forehead, and to attain a greater size than any other kind; another large
Paris breed is named the Rouennais, and has a square head; the so-called
Patagonian rabbit has remarkably short ears and a large round head.
Although I have not seen all these breeds, I feel some doubt about there
being any marked difference in the shape of their skulls. (4/8. The skulls
of these breeds are briefly described in the 'Journal of Horticulture' May
7, 1861 page 108.) English lop-eared rabbits often weigh 8 pounds or 10
pounds, and one has been exhibited weighing 18 pounds; whereas a full-sized
wild rabbit weighs only about 3 1/4 pounds. The head or skull in all the
large lop-eared rabbits examined by me is much longer relatively to its
breadth than in the wild rabbit. Many of them have loose transverse folds
of skin or dewlaps beneath the throat, which can be pulled out so as to
reach nearly to the ends of the jaws. Their ears are prodigiously
developed, and hang down on each side of their faces. A rabbit was
exhibited in 1867 with its two ears, measured from the tip of one to the
tip of the other, 22 inches in length, and each ear 5 3/8 inches in
breadth. In 1869 one was exhibited with ears, measured in the same manner,
23 1/8 in length and 5 1/2 in breadth; "thus exceeding any rabbit ever
exhibited at a prize show." In a common wild rabbit I found that the length
of two ears, from tip to tip, was 7 5/8 inches, and the breadth only 1 7/8
inch. The weight of body in the larger rabbits, and the development of
their ears, are the qualities which win prizes, and have been carefully
selected.
The hare-coloured, or, as it is sometimes called, the Belgian rabbit,
differs in nothing except colour from the other large breeds; but Mr. J.
Young, of Southampton, a great breeder of this kind, informs me that the
females, in all the specimens examined by him, had only six mammae; and
this certainly was the case with two females which came into my possession.
Mr. B.P. Brent, however, assures me that the number is variable with other
domestic rabbits. The common wild rabbit always has ten mammae. The Angora
rabbit is remarkable from the length and fineness of its fur, which even on
the soles of the feet is of considerable length. This breed is the only one
which differs in its mental qualities, for it is said to be much more
sociable than other rabbits, and the male shows no wish to destroy its
young. (4/9. 'Journal of Horticulture' 1861 page 380.) Two live rabbits
were brought to me from Moscow, of about the size of the wild species, but
with long soft fur, different from that of the Angora. These Moscow rabbits
had pink eyes and were snow-white, excepting the ears, two spots near the
nose, the upper and under surface of the tail, and the hinder tarsi, which
were blackish-brown. In short, they were coloured nearly like the so-called
Himalayan rabbits, presently to be described, and differed from them only
in the character of their fur. There are two other breeds which come true
to colour, but differ in no other respect, namely silver-greys and
chinchillas. Lastly, the Nicard or Dutch rabbit may be mentioned, which
varies in colour, and is remarkable from its small size, some specimens
weighing only 1 1/4 pounds; rabbits of this breed make excellent nurses for
other and more delicate kinds. (4/10. 'Journal of Horticulture' May 28,
1861 page 169.)
(FIGURE 5. HALF-LOP RABBIT. (Copied from E.S. Delamer's work.)
Certain characters are remarkably fluctuating, or are very feebly
transmitted by domestic rabbits: thus, one breeder tells me that with the
smaller kinds he has hardly ever raised a whole litter of the same colour:
with the large lop-eared breeds "it is impossible," says a great judge
(4/11. 'Journal of Horticulture' 1861 page 327. With respect to the ears
see Delamer on 'Pigeons and Rabbits' 1854 page 141; also 'Poultry
Chronicle' volume 2 page 499 and ditto for 1854 page 586.), "to breed true
to colour, but by judicious crossing a great deal may be done towards it.
The fancier should know how his does are bred, that is, the colour of their
parents." Nevertheless, certain colours, as we shall presently see, are
transmitted truly. The dewlap is not strictly inherited. Lop-eared rabbits,
with their ears hanging down flat on each side of the face, do not transmit
this character at all truly. Mr. Delamer remarks that, "with fancy rabbits,
when both the parents are perfectly formed, have model ears, and are
handsomely marked, their progeny do not invariably turn out the same." When
one parent, or even both, are oar-laps, that is, have their ears sticking
out at right angles, or when one parent or both are half-lops, that is,
have only one ear dependent, there is nearly as good a chance of the
progeny having both ears full-lop, as if both parents had been thus
characterised. But I am informed, if both parents have upright ears, there
is hardly a chance of a full-lop. In some half-lops the ear that hangs down
is broader and longer than the upright ear (4/12. Delamer 'Pigeons and
Rabbits' page 136. See also 'Journal of Horticulture' 1861 page 375.); so
that we have the unusual case of a want of symmetry on the two sides. This
difference in the position and size of the two ears probably indicates that
the lopping results from the great length and weight of the ear, favoured
no doubt by the weakness of the muscles consequent on disuse. Anderson
(4/13. 'An Account of the different Kinds of Sheep in the Russian
Dominions' 1794 page 39.) mentions a breed having only a single ear; and
Professor Gervais another breed destitute of ears.
We come now to the Himalayan breed, which is sometimes called Chinese,
Polish, or Russian. These pretty rabbits are white, or occasionally yellow,
excepting their ears, nose, feet, and the upper side of the tail, which are
all brownish-black; but as they have red eyes, they may be considered as
albinoes. I have received several accounts of their breeding perfectly
true. From their symmetrical marks, they were at first ranked as
specifically distinct, and were provisionally named L. nigripes. (4/14.
'Proc. Zoolog. Soc.' June 23, 1857 page 159.) Some good observers thought
that they could detect a difference in their habits, and stoutly maintained
that they formed a new species. The origin of this breed is so curious,
both in itself and as throwing some light on the complex laws of
inheritance that it is worth giving in detail. But it is first necessary
briefly to describe two other breeds: silver-greys or silver-sprigs
generally have black heads and legs, and their fine grey fur is
interspersed with numerous black and white long hairs. They breed perfectly
true, and have long been kept in warrens. When they escape and cross with
common rabbits, the product, as I hear from Mr. Wyrley Birch, of Wretham
Hall, is not a mixture of the two colours, but about half take after the
one parent, and the other half after the other parent. Secondly,
chinchillas or tame silver-greys (I will use the former name) have short,
paler, mouse or slate-coloured fur, interspersed with long, blackish,
slate-coloured, and white hairs. (4/15. 'Journal of Horticulture' April 9,
1861 page 35.) These rabbits breed perfectly true. A writer stated in 1857
(4/16. 'Cottage Gardener' 1857 page 141.) that he had produced Himalayan
rabbits in the following manner. He had a breed of chinchillas which had
been crossed with the common black rabbit, and their offspring were either
blacks or chinchillas. These latter were again crossed with other
chinchillas (which had also been crossed with silver-greys), and from this
complicated cross Himalayan rabbits were raised. From these and other
similar statements, Mr. Bartlett (4/17. Mr. Bartlett in 'Proc. Zoolog Soc.'
1861 page 40.) was led to make a careful trial in the Zoological Gardens,
and he found that by simply crossing silver-greys with chinchillas he could
always produce some few Himalayans; and the latter, notwithstanding their
sudden origin, if kept separate, bred perfectly true. But I have recently
been assured the pure silver-greys of any sub-breed occasionally produce
Himalayans.
The Himalayans, when first born, are quite white, and are then true
albinoes; but in the course of a few months they gradually assume their
dark ears, nose, feet, and tail. Occasionally, however, as I am informed by
Mr. W.A. Wooler and the Rev. W.D. Fox, the young are born of a very pale
grey colour, and specimens of such fur were sent me by the former
gentleman. The grey tint, however, disappears as the animal comes to
maturity. So that with these Himalayans there is a tendency, strictly
confined to early youth, to revert to the colour of the adult silver-grey
parent-stock. Silver-greys and chinchillas, on the other hand, present a
remarkable contrast with the Himalayans in their colour whilst quite young,
for they are born perfectly black, but soon assume their characteristic
grey or silver tints. The same thing occurs with grey horses, which, as
long as they are foals, are generally of a nearly black colour, but soon
become grey, and get whiter and whiter as they grow older. Hence the usual
rule is that Himalayans are born white and afterwards become in certain
parts of their bodies dark-coloured; whilst silver-greys are born black and
afterwards become sprinkled with white. Exceptions, however, and of a
directly opposite nature, occasionally occur in both cases. For young
silver-greys are sometimes born in warrens, as I hear from Mr. W. Birch, of
a cream-colour, but these young animals ultimately become black. The
Himalayans, on the other hand, sometimes produce, as is stated by an
experienced amateur (4/18. 'Phenomenon in Himalayan Rabbits' in 'Journal of
Horticulture' January 27, 1865 page 102.), a single black young one in a
litter; and this, before two months elapse, becomes perfectly white.
To sum up the whole curious case: wild silver-greys may be considered as
black rabbits which become grey at an early period of life. When they are
crossed with common rabbits, the offspring are said not to have blended
colours, but to take after either parent; and in this respect they resemble
black and albino varieties of most quadrupeds, which often transmit their
colours in this same manner. When they are crossed with chinchillas, that
is, with a paler sub-variety, the young are at first pure albinoes, but
soon become dark-coloured in certain parts of their bodies, and are then
called Himalayans. The young Himalayans, however, are sometimes at first
either pale grey or completely black, in either case changing after a time
to white. In a future chapter I shall advance a large body of facts showing
that, when two varieties are crossed both of which differ in colour from
their parent-stock, there is a strong tendency in the young to revert to
the aboriginal colour; and what is very remarkable, this reversion
occasionally supervenes, not before birth, but during the growth of the
animal. Hence, if it could be shown that silver-greys and chinchillas were
the offspring of a cross between a black and albino variety with the
colours intimately blended--a supposition in itself not improbable, and
supported by the circumstance of silver-greys in warrens sometimes
producing creamy-white young, which ultimately become black--then all the
above given paradoxical facts on the changes of colour in silver-greys and
in their descendants the Himalayans would come under the law of reversion,
supervening at different periods of growth and in different degrees, either
to the original black or to the original albino parent-variety.
It is, also, remarkable that Himalayans, though produced so suddenly; breed
true. But as, whilst young, they are albinoes, the case falls under a very
general rule; albinism being well known to be strongly inherited, for
instance with white mice and many other quadrupeds, and even white flowers.
But why, it may be asked, do the ears, tail, nose, and feet, and no other
part of the body, revert to a black colour? This apparently depends on a
law, which generally holds good, namely, that characters common to many
species of a genus--and this, in fact, implies long inheritance from the
ancient progenitor of the genus--are found to resist variation, or to
reappear if lost, more persistently than the characters which are confined
to the separate species. Now, in the genus Lepus, a large majority of the
species have their ears and the upper surface of the tail tinted black; but
the persistence of these marks is best seen in those species which in
winter become white: thus, in Scotland the L. variabilis (4/19. G.R.
Waterhouse 'Natural History of Mammalia: Rodents' 1846 pages 52, 60, 105.)
in its winter dress has a shade of colour on its nose, and the tips of its
ears are black: in the L. tibetanus the ears are black, the upper surface
of the tail greyish-black, and the soles of the feet brown: in L. glacialis
the winter fur is pure white, except the soles of the feet and the points
of the ears. Even in the variously-coloured fancy rabbits we may often
observe a tendency in these same parts to be more darkly tinted than the
rest of the body. Thus the several coloured marks on the Himalayan rabbits,
as they grow old, are rendered intelligible. I may add a nearly analogous
case: fancy rabbits very often have a white star on their foreheads; and
the common English hare, whilst young, generally has, as I have myself
observed, a similar white star on its forehead.
When variously coloured rabbits are set free in Europe, and are thus placed
under their natural conditions, they generally revert to the aboriginal
grey colour; this may be in part due to the tendency in all crossed
animals, as lately observed, to revert to their primordial state. But this
tendency does not always prevail; thus silver-grey rabbits are kept in
warrens, and remain true though living almost in a state of nature; but a
warren must not be stocked with both silver-greys and common rabbits;
otherwise "in a few years there will be none but common greys surviving."
(4/20. Delamer on 'Pigeons and Rabbits' page 114.) When rabbits run wild in
foreign countries under new conditions of life, they by no means always
revert to their aboriginal colour. In Jamaica the feral rabbits are
described as having been "slate-coloured, deeply tinted with sprinklings of
white on the neck, on the shoulders, and on the back; softening off to
blue-white under the breast and belly." (4/21. Gosse 'Sojourn in Jamaica'
1851 page 441 as described by an excellent observer, Mr. R. Hill. This is
the only known case in which rabbits have become feral in a hot country.
They can be kept, however, at Loanda (see Livingstone 'Travels' page 407).
In parts of India, as I am informed by Mr. Blyth, they breed well.) But in
this tropical island the conditions were not favourable to their increase,
and they never spread widely, and are now extinct, as I hear from Mr. R.
Hill, owing to a great fire which occurred in the woods. Rabbits during
many years have run wild in the Falkland Islands; they are abundant in
certain parts, but do not spread extensively. Most of them are of the
common grey colour; a few, as I am informed by Admiral Sulivan, are hare-
coloured, and many are black, often with nearly symmetrical white marks on
their faces. Hence, M. Lesson described the black variety as a distinct
species, under the name of Lepus magellanicus, but this, as I have
elsewhere shown, is an error. (4/22. Darwin 'Journal of Researches' page
193; and 'Zoology of the Voyage of the Beagle: Mammalia' page 92.) Within
recent times the sealers have stocked some of the small outlying islets in
the Falkland group with rabbits; and on Pebble Islet, as I hear from
Admiral Sulivan, a large proportion are hare-coloured, whereas on Rabbit
Islet a large proportion are of a bluish colour, which is not elsewhere
seen. How the rabbits were coloured which were turned out of these islets
is not known.
The rabbits which have become feral on the island of Porto Santo, near
Madeira, deserve a fuller account. In 1418 or 1419, J. Gonzales Zarco
(4/23. Kerr 'Collection of Voyages' volume 2 page 177: page 205 for Cada
Mosto. According to a work published in Lisbon in 1717 entitled 'Historia
Insulana' written by a Jesuit, the rabbits were turned out in 1420. Some
authors believe that the island was discovered in 1413.) happened to have a
female rabbit on board which had produced young during the voyage, and he
turned them all out on the island. These animals soon increased so rapidly,
that they became a nuisance, and actually caused the abandonment of the
settlement. Thirty-seven years subsequently, Cada Mosto describes them as
innumerable; nor is this surprising, as the island was not inhabited by any
beast of prey or by any terrestrial mammal. We do not know the character of
the mother-rabbit; but it was probably the common domesticated kind. The
Spanish peninsula, whence Zarco sailed, is known to have abounded with the
common wild species at the most remote historical period; and as these
rabbits were taken on board for food, it is improbable that they should
have been of any peculiar breed. That the breed was well domesticated is
shown by the doe having littered during the voyage. Mr. Wollaston, at my
request, brought home two of these feral rabbits in spirits of wine; and,
subsequently, Mr. W. Haywood sent to me three more specimens in brine, and
two alive. These seven specimens, though caught at different periods,
closely resembled each other. They were full grown, as shown by the state
of their bones. Although the conditions of life in Porto Santo are
evidently highly favourable to rabbits, as proved by their extraordinarily
rapid increase, yet they differ conspicuously in their small size from the
wild English rabbit. Four English rabbits, measured from the incisors to
the anus, varied between 17 and 17 3/4 inches in length; whilst two of the
Porto Santo rabbits were only 14 1/2 and 15 inches in length. But the
decrease in size is best shown by weight; four wild English rabbits
averaged 3 pounds 5 ounces, whilst one of the Porto Santo rabbits, which
had lived for four years in the Zoological Gardens, but had become thin,
weighed only 1 pound 9 ounces. A fairer test is afforded by the comparison
of the well-cleaned limb-bones of a Porto Santo rabbit killed on the island
with the same bones of a wild English rabbit of average size, and they
differed in the proportion of rather less than five to nine. So that the
Porto Santo rabbits have decreased nearly three inches in length, and
almost half in weight of body. (4/24. Something of the same kind has
occurred on the island of Lipari, where, according to Spallanzani ('Voyage
dans les deux Siciles' quoted by Godron 'De l'Espece' page 364), a
countryman turned out some rabbits which multiplied prodigiously, but, says
Spallanzani, "les lapins de l'ile de Lipari sont plus petits que ceux qu'on
eleve en domesticite.") The head has not decreased in length proportionally
with the body; and the capacity of the brain case is, as we shall hereafter
see, singularly variable. I prepared four skulls, and these resembled each
other more closely than do generally the skulls of wild English rabbits;
but the only difference in structure which they presented was that the
supra-orbital processes of the frontal bones were narrower.
In colour the Porto Santo rabbit differs considerably from the common
rabbit; the upper surface is redder, and is rarely interspersed with any
black or black-tipped hairs. The throat and certain parts of the under
surface, instead of being pure white, are generally pale grey or leaden
colour. But the most remarkable difference is in the ears and tail; I have
examined many fresh English rabbits, and the large collection of skins in
the British Museum from various countries, and all have the upper surface
of the tail and the tips of the ears clothed with blackish-grey fur; and
this is given in most works as one of the specific characters of the
rabbit. Now in the seven Porto Santo rabbits the upper surface of the tail
was reddish-brown, and the tips of the ears had no trace of the black
edging. But here we meet with a singular circumstance: in June, 1861 I
examined two of these rabbits recently sent to the Zoological Gardens, and
their tails and ears were coloured as just described; but when one of their
dead bodies was sent to me in February, 1865, the ears were plainly edged,
and the upper surface of the tail was covered with blackish-grey fur, and
the whole body was much less red; so that under the English climate this
individual rabbit had recovered the proper colour of its fur in rather less
than four years!
The two little Porto Santo rabbits, whilst alive in the Zoological Gardens,
had a remarkably different appearance from the common kind. They were
extraordinarily wild and active, so that many persons exclaimed on seeing
them that they were more like large rats than rabbits. They were nocturnal
to an unusual degree in their habits, and their wildness was never in the
least subdued; so that the superintendent, Mr. Bartlett, assured me that he
had never had a wilder animal under his charge. This is a singular fact,
considering that they are descended from a domesticated breed. I was so
much surprised at it, that I requested Mr. Haywood to make inquiries on the
spot, whether they were much hunted by the inhabitants, or persecuted by
hawks, or cats, or other animals; but this is not the case, and no cause
can be assigned for their wildness. They live both on the central, higher
rocky land and near the sea-cliffs, and, from being exceedingly shy and
timid, seldom appear in the lower and cultivated districts. They are said
to produce from four to six young at a birth, and their breeding season is
in July and August. Lastly, and this is a highly remarkable fact, Mr.
Bartlett could never succeed in getting these two rabbits, which were both
males, to associate or breed with the females of several breeds which were
repeatedly placed with them.
If the history of these Porto Santo rabbits had not been known, most
naturalists, on observing their much reduced size, their colour, reddish
above and grey beneath, their tails and ears not tipped with black, would
have ranked them as a distinct species. They would have been strongly
confirmed in this view by seeing them alive in the Zoological Gardens, and
hearing that they refused to couple with other rabbits. Yet this rabbit,
which there can be little doubt would thus have been ranked as a distinct
species, as certainly originated since the year 1420. Finally, from the
three cases of the rabbits which have run wild in Porto Santo, Jamaica, and
the Falkland Islands, we see that these animals do not, under new
conditions of life, revert to or retain their aboriginal character, as is
so generally asserted to be the case by most authors.
OSTEOLOGICAL CHARACTERS.
When we remember, on the one hand, how frequently it is stated that
important parts of the structure never vary; and, on the other hand, on
what small differences in the skeleton fossil species have often been
founded, the variability of the skull and of some other bones in the
domesticated rabbit well deserves attention. It must not be supposed that
the more important differences immediately to be described strictly
characterise any one breed; all that can be said is, that they are
generally present in certain breeds. We should bear in mind that selection
has not been applied to fix any character in the skeleton, and that the
animals have not had to support themselves under uniform habits of life. We
cannot account for most of the differences in the skeleton; but we shall
see that the increased size of the body, due to careful nurture and
continued selection, has affected the head in a particular manner. Even the
elongation and lopping of the ears have influenced in a small degree the
form of the whole skull. The want of exercise has apparently modified the
proportional length of the limbs in comparison with that of the body.
[As a standard of comparison, I prepared skeletons of two wild rabbits from
Kent, one from the Shetland Islands, and one from Antrim in Ireland. As all
the bones in these four specimens from such distant localities closely
resembled each other, presenting scarcely any appreciable difference, it
may be concluded that the bones of the wild rabbit are generally uniform in
character.
SKULL.
I have carefully examined skulls of ten large lop-eared rabbits, and of
five common domestic rabbits, which latter differ from the lop-eared only
in not having such large bodies or ears, yet both larger than in the wild
rabbit. First for the ten lop-eared rabbits: in all these the skull is
remarkably elongated in comparison with its breadth. In a wild rabbit the
length was 3.15 inches, in a large fancy rabbit 4.3; whilst the breadth of
the cranium enclosing the brain was in both almost exactly the same. Even
by taking as the standard of comparison the widest part of the zygomatic
arch, the skulls of the lop-eared are proportionally to their breadth
three-quarters of an inch too long. The depth of the head has increased
almost in the same proportion with the length; it is the breadth alone
which has not increased. The parietal and occipital bones enclosing the
brain are less arched, both in a longitudinal and transverse line, than in
the wild rabbit, so that the shape of the cranium is somewhat different.
The surface is rougher, less cleanly sculptured, and the lines of sutures
are more prominent.
Although the skulls of the large lop-eared rabbits in comparison with those
of the wild rabbit are much elongated relatively to their breadth, yet,
relatively to the size of body, they are far from elongated. The lop-eared
rabbits which I examined were, though not fat, more than twice as heavy as
the wild specimens; but the skull was very far from being twice as long.
Even if we take the fairer standard of the length of body, from the nose to
the anus, the skull is not on an average as long as it ought to be by a
third of an inch. In the small feral Porto Santo rabbit, on the other hand,
the head relatively to the length of body is about a quarter of an inch too
long.
This elongation of the skull relatively to its breadth, I find a universal
character, not only with the large lop-eared rabbits, but in all the
artificial breeds; as is well seen in the skull of the Angora. I was at
first much surprised at the fact, and could not imagine why domestication
could produce this uniform result; but the explanation seems to lie in the
circumstance that during a number of generations the artificial races have
been closely confined, and have had little occasion to exert either their
senses, or intellect, or voluntary muscles; consequently the brain, as we
shall presently more fully see, has not increased relatively with the size
of body. As the brain has not increased, the bony case enclosing it has not
increased, and this has evidently affected through correlation the breadth
of the entire skull from end to end.
(FIGURE 6. SKULL OF WILD RABBIT, of natural size.
FIGURE 7. SKULL OF LARGE LOP-EARED RABBIT, of natural size.
FIGURE 8. PART OF ZYGOMATIC ARCH, showing the projecting end of the malar
bone of the auditory meatus: of natural size. Upper figure, Wild Rabbit.
Lower figure, Lop-eared, hare-coloured Rabbit.
FIGURE 9. POSTERIOR END OF SKULL, of natural size, showing the inter-
parietal bone. A. Wild Rabbit. B. Feral Rabbit from island of P. Santo,
near Madeira. C. Large Lop-eared Rabbit.)
In all the skulls of the large lop-eared rabbits, the supra-orbital plates
or processes of the frontal bones are much broader than in the wild rabbit,
and they generally project more upwards. In the zygomatic arch the
posterior or projecting point of the malar-bone is broader and blunter; and
in the specimen, figure 8, it is so in a remarkable degree. This point
approaches nearer to the auditory meatus than in the wild rabbit, as may be
best seen in figure 8; but this circumstance mainly depends on the changed
direction of the meatus. The inter-parietal bone (see figure 9) differs
much in shape in the several skulls; generally it is more oval, that is
more extended in the line of the longitudinal axis of the skull, than in
the wild rabbit. The posterior margin of "the square raised platform"
(4/25. Waterhouse 'Nat. Hist. Mammalia' volume 2 page 36.) of the occiput,
instead of being truncated, or projecting slightly as in the wild rabbit,
is in most lop-eared rabbits pointed, as in figure 9, C. The paramastoids
relatively to the size of the skull are generally much thicker than in the
wild rabbit.
(FIGURE 10. OCCIPITAL FORAMEN, of natural size, in--A. Wild Rabbit; B.
Large Lop-eared Rabbit.)
The occipital foramen (figure 10) presents some remarkable differences: in
the wild rabbit, the lower edge between the condyles is considerably and
almost angularly hollowed out, and the upper edge is deeply and squarely
notched; hence the longitudinal axis exceeds the transverse axis. In the
skulls of the lop-eared rabbits the transverse axis exceeds the
longitudinal; for in none of these skulls was the lower edge between the
condyles so deeply hollowed out; in five of them there was no upper square
notch, in three there was a trace of the notch, and in two alone it was
well developed. These differences in the shape of the foramen are
remarkable, considering that it gives passage to so important a structure
as the spinal marrow, though apparently the outline of the latter is not
affected by the shape of the passage.
(FIGURE 11. SKULL, of natural size, of Half-lop Rabbit, showing the
different direction of the auditory meatus on the two sides, and the
consequent general distortion of the skull. The left ear of the animal (or
right side of figure) lopped forwards.)
In all the skulls of the large lop-eared rabbits, the bony auditory meatus
is conspicuously larger than in the wild rabbit. In a skull 4.3 inches in
length, and which barely exceeded in breadth the skull of a wild rabbit
(which was 3.15 inches in length), the longer diameter of the meatus was
exactly twice as great. The orifice is more compressed, and its margin on
the side nearest the skull stands up higher than the outer side. The whole
meatus is directed more forwards. As in breeding lop-eared rabbits the
length of the ears, and their consequent lopping and lying flat on the
face, are the chief points of excellence, there can hardly be a doubt that
the great change in the size, form, and direction of the bony meatus,
relatively to this same part in the wild rabbit, is due to the continued
selection of individuals having larger and larger ears. The influence of
the external ear on the bony meatus is well shown in the skulls (I have
examined three) of half-lops (see figure 5), in which one ear stands
upright, and the other and longer ear hangs down; for in these skulls there
was a plain difference in the form and direction of the bony meatus on the
two sides. But it is a much more interesting fact, that the changed
direction and increased size of the bony meatus have slightly affected on
the same side the structure of the whole skull. I here give a drawing
(figure 11) of the skull of a half-lop; and it may be observed that the
suture between the parietal and frontal bones does not run strictly at
right angles to the longitudinal axis of the skull; the left frontal bone
projects beyond the right one; both the posterior and anterior margins of
the left zygomatic arch on the side of the lopping ear stand a little in
advance of the corresponding bones on the opposite side. Even the lower jaw
is affected, and the condyles are not quite symmetrical, that on the left
standing a little in advance of that on the right. This seems to me a
remarkable case of correlation of growth. Who would have surmised that by
keeping an animal during many generations under confinement, and so leading
to the disuse of the muscles of the ears, and by continually selecting
individuals with the longest and largest ears, he would thus indirectly
have affected almost every suture in the skull and the form of the lower
jaw!
In the large lop-eared rabbits the only difference in the lower jaw, in
comparison with that of the wild rabbit, is that the posterior margin of
the ascending ramus is broader and more inflected. The teeth in neither jaw
present any difference, except that the small incisors, beneath the large
ones, are proportionately a little longer. The molar teeth have increased
in size proportionately with the increased width of the skull, measured
across the zygomatic arch, and not proportionally with its increased
length. The inner line of the sockets of the molar teeth in the upper jaw
of the wild rabbit forms a perfectly straight line; but in some of the
largest skulls of the lop-eared this line was plainly bowed inwards. In one
specimen there was an additional molar tooth on each side of the upper jaw,
between the molars and premolars; but these two teeth did not correspond in
size; and as no rodent has seven molars, this is merely a monstrosity,
though a curious one.
The five other skulls of common domestic rabbits, some of which approach in
size the above-described largest skulls, whilst the others exceed but
little those of the wild rabbit, are only worth notice as presenting a
perfect gradation in all the above-specified differences between the skulls
of the largest lop-eared and wild rabbits. In all, however, the supra-
orbital plates are rather larger, and in all the auditory meatus is larger,
in conformity with the increased size of the external ears, than in the
wild rabbit. The lower notch in the occipital foramen in some was not so
deep as in the wild rabbit, but in all five skulls the upper notch was well
developed.
The skull of the Angora rabbit, like the latter five skulls, is
intermediate in general proportions, and in most other characters, between
those of the largest lop-eared and wild rabbits. It presents only one
singular character: though considerably longer than the skull of the wild
rabbit, the breadth measured within the posterior supra-orbital fissures is
nearly a third less than in the wild. The skulls of the silver-grey, and
chinchilla and Himalayan rabbits are more elongated than in the wild, with
broader supra-orbital plates, but differ little in any other respect,
excepting that the upper and lower notches of the occipital foramen are not
so deep or so well developed. The skull of the Moscow rabbit scarcely
differs at all from that of the wild rabbit. In the Porto Santo feral
rabbits the supra-orbital plates are generally narrower and more pointed
than in our wild rabbits.
As some of the largest lop-eared rabbits of which I prepared skeletons were
coloured almost like hares, and as these latter animals and rabbits have,
as it is affirmed, been recently crossed in France, it might be thought
that some of the above-described characters had been derived from a cross
at a remote period with the hare. Consequently I examined skulls of the
hare, but no light could thus be thrown on the peculiarities of the skulls
of the larger rabbits. It is, however, an interesting fact, as illustrating
the law that varieties of one species often assume the characters of other
species of the same genus, that I found, on comparing the skulls of ten
species of hares in the British Museum, that they differed from each other
chiefly in the very same points in which domestic rabbits vary,--namely, in
general proportions, in the form and size of the supra-orbital plates, in
the form of the free end of the malar bone, and in the line of suture
separating the occipital and frontal bones. Moreover two eminently variable
characters in the domestic rabbit, namely, the outline of the occipital
foramen and the shape of the "raised platform" of the occiput, were
likewise variable in two instances in the same species of hare.
VERTEBRAE.
The number is uniform in all the skeletons which I have examined, with two
exceptions, namely, in one of the small feral Porto Santo rabbits and in
one of the largest lop-eared kinds; both of these had as usual seven
cervical, twelve dorsal with ribs, but, instead of seven lumbar, both had
eight lumbar vertebrae. This is remarkable, as Gervais gives seven as the
number for the whole genus Lepus. The caudal vertebrae apparently differ by
two or three, but I did not attend to them, and they are difficult to count
with certainty.
(FIGURE 12. ATLAS VERTEBRAE, of natural size; inferior surface viewed
obliquely. Upper figure, Wild Rabbit. Lower figure, Hare-coloured, large,
Lop-eared Rabbit, a, supra-median, atlantoid process; b, infra-median
process.)
In the first cervical vertebra, or atlas, the anterior margin of the neural
arch varies a little in wild specimens, being either nearly smooth, or
furnished with a small supra-median atlantoid process; I have figured a
specimen with the largest process (a) which I have seen; but it will be
observed how inferior this is in size and different in shape to that in a
large lop-eared rabbit. In the latter, the infra-median process (b) is also
proportionally much thicker and longer. The alae are a little squarer in
outline.
(FIGURE 13. THIRD CERVICAL VERTEBRAE, of natural size, of: A. Wild Rabbit;
B. Hare-coloured, large, Lop-eared Rabbit, a, a, inferior surface; b, b,
anterior articular surfaces.)
THIRD CERVICAL VERTEBRA.
In the wild rabbit (figure 13, A a) this vertebra, viewed on the inferior
surface, has a transverse process, which is directed obliquely backwards,
and consists of a single pointed bar; in the fourth vertebra this process
is slightly forked in the middle. In the large lop-eared rabbits this
process (B a) is forked in the third vertebra, as in the fourth of the wild
rabbit. But the third cervical vertebrae of the wild and lop-eared (A b, B
b) rabbits differ more conspicuously when their anterior articular surfaces
are compared; for the extremities of the antero-dorsal processes in the
wild rabbit are simply rounded, whilst in the lop-eared they are trifid,
with a deep central pit. The canal for the spinal marrow in the lop-eared
(B b) is more elongated in a transverse direction than in the wild rabbit;
and the passages for the arteries are of a slightly different shape. These
several differences in this vertebra seem to me well deserving attention.
FIRST DORSAL VERTEBRA.
Its neural spine varies in length in the wild rabbit; being sometimes very
short, but generally more than half as long as that of the second dorsal;
but I have seen it in two large lop-eared rabbits three-fourths of the
length of that of the second dorsal vertebra.
(FIGURE 14. DORSAL VERTEBRAE, from sixth to tenth inclusive, of natural
size, viewed laterally. A. Wild Rabbit. B. Large, Hare-coloured, so called
Spanish Rabbit.)
NINTH AND TENTH DORSAL VERTEBRAE.
In the wild rabbit the neural spine of the ninth vertebra is just
perceptibly thicker than that of the eighth; and the neural spine of the
tenth is plainly thicker and shorter than those of all the anterior
vertebrae. In the large lop-eared rabbits the neural spines of the tenth,
ninth, and eighth vertebrae, and even in a slight degree that of the
seventh, are very much thicker, and of somewhat different shape, in
comparison with those of the wild rabbit. So that this part of the
vertebral column differs considerably in appearance from the same part in
the wild rabbit, and closely resembles in an interesting manner these same
vertebrae in some species of hares. In the Angora, Chinchilla, and
Himalayan rabbits, the neural spines of the eighth and ninth vertebrae are
in a slight degree thicker than in the wild. On the other hand, in one of
the feral Porto Santo rabbits, which in most of its characters deviates
from the common wild rabbit, in a direction exactly opposite to that
assumed by the large lop-eared rabbits, the neural spines of the ninth and
tenth vertebrae were not at all larger than those of the several anterior
vertebra. In this same Porto Santo specimen there was no trace in the ninth
vertebra of the anterior lateral processes (see figure 14), which are
plainly developed in all British wild rabbits, and still more plainly
developed in the large lop-eared rabbits. In a half-wild rabbit from Sandon
Park (4/26. These rabbits have run wild for a considerable time in Sandon
Park, and in other places in Staffordshire and Shropshire. They originated,
as I have been informed by the gamekeeper, from variously-coloured domestic
rabbits which had been turned out. They vary in colour; but many are
symmetrically coloured, being white with a streak along the spine, and with
the ears and certain marks about the head of a blackish-grey tint. They
have rather longer bodies than common rabbits), a haemal spine was
moderately well developed on the under side of the twelfth dorsal vertebra,
and I have seen this in no other specimen.
LUMBAR VERTEBRAE.
I have stated that in two cases there were eight instead of seven lumbar
vertebrae. The third lumbar vertebrae in one skeleton of a wild British
rabbit, and in one of the Porto Santo feral rabbits, had a haemal spine;
whilst in four skeletons of large lop-eared rabbits, and in the Himalayan
rabbit, this same vertebra had a well developed haemal spine.
PELVIS.
In four wild specimens this bone was almost absolutely identical in shape;
but in several domesticated breeds shades of differences could be
distinguished. In the large lop-eared rabbits, the whole upper part of the
ilium is straighter, or less splayed outwards, than in the wild rabbit; and
the tuberosity on the inner lip of the anterior and upper part of the ilium
is proportionally more prominent.
(FIGURE 15. TERMINAL BONE OF STERNUM, of natural size, A. Wild Rabbit. B.
Hare-coloured, Lop-eared Rabbit. C. Hare-coloured Spanish Rabbit. (N.B. The
left-hand angle of the upper articular extremity of B was broken, and has
been accidentally thus represented.))
STERNUM.
The posterior end of the posterior sternal bone in the wild rabbit (figure
15, A) is thin and slightly enlarged; in some of the large lop-eared
rabbits (B) it is much more enlarged towards the extremity; whilst in other
specimens (C) it keeps nearly of the same breadth from end to end, but is
much thicker at the extremity.
(FIGURE 16. ACROMION OF SCAPULA, of natural size. A. Wild Rabbit. B, C, D,
Large, Lop-eared Rabbits.)
SCAPULA.
The acromion sends out a rectangular bar, ending in an oblique knob, which
latter in the wild rabbit (figure 16, A) varies a little in shape and size,
as does the apex of the acromion in sharpness, and the part just below the
rectangular bar in breadth. But the variations in these respects in the
wild rabbit are very slight: whilst in the large lop-eared rabbits they are
considerable. Thus in some specimens (B) the oblique terminal knob is
developed into a short bar, forming an obtuse angle with the rectangular
bar. In another specimen (C) these two unequal bars form nearly a straight
line. The apex of the acromion varies much in breadth and sharpness, as may
be seen by comparing figures B, C, and D.
LIMBS.
In these I could detect no variation; but the bones of the feet were too
troublesome to compare with much care.]
I have now described all the differences in the skeletons which I have
observed. It is impossible not to be struck with the high degree of
variability or plasticity of many of the bones. We see how erroneous the
often-repeated statement is, that only the crests of the bones which give
attachment to muscles vary in shape, and that only parts of slight
importance become modified under domestication. No one will say, for
instance, that the occipital foramen, or the atlas, or the third cervical
vertebra is a part of slight importance. If the several vertebrae of the
wild and lop-eared rabbits, of which figures have been given, had been
found fossil, palaeontologists would have declared without hesitation that
they had belonged to distinct species.
[THE EFFECTS OF THE USE AND DISUSE OF PARTS.
In the large lop-eared rabbits the relative proportional length of the
bones of the same leg, and of the front and hind legs compared with each
other, have remained nearly the same as in the wild rabbit; but in weight,
the bones of the hind legs apparently have not increased in due proportion
with the front legs. The weight of the whole body in the large rabbits
examined by me was from twice to twice and a half as great as that of the
wild rabbit; and the weight of the bones of the front and hind limbs taken
together (excluding the feet, on account of the difficulty of cleaning so
many small bones) has increased in the large lop-eared rabbits in nearly
the same proportion; consequently in due proportion to the weight of body
which they have to support. If we take the length of the body as the
standard of comparison, the limbs of the large rabbits have not increased
in length in due proportion by one inch and a half. Again, if we take as
the standard of comparison the length of the skull, which, as we have
before seen, has not increased in length in due proportion to the length of
body, the limbs will be found to be, proportionally with those of the wild
rabbit, from half to three-quarters of an inch too short. Hence, whatever
standard of comparison be taken, the limb-bones of the large lop-eared
rabbits have not increased in length, though they have in weight, in full
proportion to the other parts of the frame; and this, I presume, may be
accounted for by the inactive life which during many generations they have
spent. Nor has the scapula increased in length in due proportion to the
increased length of the body.
The capacity of the osseous case of the brain is a more interesting point,
to which I was led to attend by finding, as previously stated, that with
all domesticated rabbits the length of the skull relatively to its breadth
has greatly increased in comparison with that of the wild rabbits. If we
had possessed a large number of domesticated rabbits of nearly the same
size with the wild rabbits, it would have been a simple task to have
measured and compared the capacities of their skulls. But this is not the
case: almost all the domestic breeds have larger bodies than wild rabbits,
and the lop-eared kinds are more than double their weight. As a small
animal has to exert its senses, intellect, and instincts equally with a
large animal, we ought not by any means to expect an animal twice or thrice
as large as another to have a brain of double or treble the size. (4/27.
See Prof. Owen's remarks on this subject in his paper on the 'Zoological
Significance of the Brain, etc., of Man, etc.' read before Brit.
Association 1862: with respect to Birds see 'Proc. Zoolog. Soc.' January
11, 1848 page 8.) Now, after weighing the bodies of four wild rabbits, and
of four large but not fattened lop-eared rabbits, I find that on an average
the wild are to the lop-eared in weight as 1 to 2.17; in average length of
body as 1 to 1.41; whilst in capacity of skull they are as 1 to 1.15. Hence
we see that the capacity of the skull, and consequently the size of the
brain, has increased but little, relatively to the increased size of the
body; and this fact explains the narrowness of the skull relatively to its
length in all domestic rabbits.
TABLE 3: MEASUREMENTS OF WILD AND SEMI-WILD RABBITS.
I. Length of Skull (inches).
II. Length of Body from Incisors to Anus (inches).
III. Weight of whole Body (pounds and ounces).
IV. Capacity of Skull measured by Small Shot (grains).
V. Capacity calculated according to Length of Skull relatively to that of
No. 1 (Wild Rabbit, Kent) (grains).
VI. Difference between actual and calculated capacities of Skulls (grains).
VII. Showing how much per cent the Brain, by calculation according to the
length of the Skull is too light (-) or too heavy (+), relatively to the
Brain of the Wild Rabbit No. 1.
NAME OF BREED: I. II. III. IV. V. VI.
VII.
WILD AND SEMI-WILD RABBITS:
1. Wild Rabbit, Kent: 3.15 17.4 3,5 972 .. ..
+2
2. Wild Rabbit, Shetland Islands: 3.15 .. .. 979 .. ..
+2
3. Wild Rabbit, Ireland: 3.15 .. .. 992 .. ..
+2
4. Domestic rabbit, run wild,
Sandon: 3.15 18.5 .. 977 .. ..
+2
5. Wild, common variety,
small specimen, Kent: 2.96 17.0 2,14 875 913 38 -
4
6. Wild, fawn-coloured variety,
Scotland: 3.1 .. .. 918 950 32 -
3
7. Silver-grey, small specimen,
Thetford warren: 2.95 15.5 2,11 938 910 28
+3
8. Feral rabbit, Porto Santo: 2.83 .. .. 893 873 20
+2
9. Feral rabbit, Porto Santo: 2.85 .. .. 756 879 123 -
16
10.Feral rabbit, Porto Santo: 2.95 .. .. 835 910 75 -
9
Average of three Porto Santo
rabbits: 2.88 .. .. 828 888 60 -
7
DOMESTIC RABBITS:
11.Himalayan: 3.5 20.5 .. 963 1080 117 -
12
12.Moscow: 3.25 17.0 3,8 803 1002 199 -
24
13.Angora: 3.5 19.5 3,1 697 1080 383 -
54
14.Chinchilla: 3.65 22.0 .. 995 1126 131 -
13
15.Large lop-eared: 4.1 24.5 7,0 1065 1265 200 -
18
16.Large lop-eared: 4.1 25.0 7,13 1153 1265 112 -
9
17.Large lop-eared: 4.07 .. .. 1037 1255 218 -
21
18.Large lop-eared: 4.1 25.0 7,4 1208 1265 57 -
4
19.Large lop-eared: 4.3 .. .. 1232 1326 94 -
7
20.Large lop-eared: 4.25 .. .. 1124 1311 187 -
16
21.Large hare-coloured: 3.86 24.0 6,14 1131 1191 60 -
5
22.Average of above seven large
lop-eared rabbits: 4.11 24.62 7,4 1136 1268 132 -
11
23.Hare (L. timidus)
English specimen: 3.61 7,0 1315
24.Hare (L. timidus)
German specimen: 3.82 7,0 1455
In the upper half of Table 3 I have given the measurements of the skull of
ten wild rabbits; and in the lower half, of eleven thoroughly domesticated
kinds. As these rabbits differ so greatly in size, it is necessary to have
some standard by which to compare the capacities of their skulls. I have
selected the length of skull as the best standard, for in the larger
rabbits it has not, as already stated, increased in length so much as the
body; but as the skull, like every other part, varies in length, neither it
nor any other part affords a perfect standard.
In the first column of figures the extreme length of the skull is given in
inches and decimals. I am aware that these measurements pretend to greater
accuracy than is possible; but I have found it the least trouble to record
the exact length which the compass gave. The second and third columns give
the length and weight of body, whenever these observations were made. The
fourth column gives the capacity of the skull by the weight of small shot
with which the skulls were filled; but it is not pretended that these
weights are accurate within a few grains. In the fifth column the capacity
is given which the skull ought to have had by calculation, according to the
length of skull, in comparison with that of the wild rabbit No. 1; in the
sixth column the difference between the actual and calculated capacities,
and in the seventh the percentage of increase or decrease, are given. For
instance, as the wild rabbit No. 5 has a shorter and lighter body than the
wild rabbit No. 1, we might have expected that its skull would have had
less capacity; the actual capacity, as expressed by the weight of shot, is
875 grains, which is 97 grains less than that of the first rabbit. But
comparing these two rabbits by the length of their skulls, we see that in
No. 1 the skull is 3.15 inches in length, and in No. 5 2.96 inches in
length; according to this ratio, the brain of No. 5 ought to have had a
capacity of 913 grains of shot, which is above the actual capacity, but
only by 38 grains. Or, to put the case in another way (as in column VII),
the brain of this small rabbit, No. 5, for every 100 grains of weight is
only 4 grains too light,--that is, it ought, according to the standard
rabbit No. 1, to have been 4 per cent heavier. I have taken the rabbit No.
1 as the standard of comparison because, of the skulls having a full
average length, this has the least capacity; so that it is the least
favourable to the result which I wish to show, namely, that the brain in
all long-domesticated rabbits has decreased in size, either actually, or
relatively to the length of the head and body, in comparison with the brain
of the wild rabbit. Had I taken the Irish rabbit, No. 3, as the standard,
the following results would have been somewhat more striking.
Turning to Table 3: the first four wild rabbits have skulls of the same
length, and these differ but little in capacity. The Sandon rabbit (No. 4)
is interesting, as, though now wild, it is known to be descended from a
domesticated breed, as is still shown by its peculiar colouring and longer
body; nevertheless the skull has recovered its normal length and full
capacity. The next three rabbits are wild, but of small size, and they all
have skulls with slightly lessened capacities. The three Porto Santo feral
rabbits (Nos. 8 to 10) offer a perplexing case; their bodies are greatly
reduced in size, as in a lesser degree are their skulls in length and in
actual capacity, in comparison with the skulls of wild English rabbits. But
when we compare the capacities of the skull in the three Porto Santo
rabbits, we observe a surprising difference, which does not stand in any
relation to the slight difference in the length of their skulls, nor, as I
believe, to any difference in the size of their bodies; but I neglected
weighing separately their bodies. I can hardly suppose that the medullary
matter of the brain in these three rabbits, living under similar
conditions, can differ as much as is indicated by the proportional
difference of capacity in their skulls; nor do I know whether it is
possible that one brain may contain considerably more fluid than another.
Hence I can throw no light on this case.
Looking to the lower half of Table 3, which gives the measurements of
domesticated rabbits, we see that in all the capacity of the skull is less,
but in very various degrees, than might have been anticipated according to
the length of their skulls, relatively to that of the wild rabbit No. 1. In
line 22 the average measurements of seven large lop-eared rabbits are
given. Now the question arises, has the average capacity of the skull in
these seven large rabbits increased as much as might have been expected
from the greatly increased size of body. We may endeavour to answer this
question in two ways: in the upper half of the Table we have measurements
of the skulls of six small wild rabbits (Nos. 5 to 10), and we find that on
an average the skulls are .18 of an inch shorter, and in capacity 91 grains
less, than the average length and capacity of the three first wild rabbits
on the list. The seven large lop-eared rabbits, on an average, have skulls
4.11 inches in length, and 1136 grains in capacity; so that these skulls
have increased in length more than five times as much as the skulls of the
six small wild rabbits have decreased in length; hence we might have
expected that the skulls of the large lop-eared rabbits would have
increased in capacity five times as much as the skulls of the six small
rabbits have decreased in capacity; and this would have given an average
increased capacity of 455 grains, whilst the real average increase is only
155 grains. Again, the large lop-eared rabbits have bodies of nearly the
same weight and size as the common hare, but their heads are longer;
consequently, if the lop-eared rabbits had been wild, it might have been
expected that their skulls would have had nearly the same capacity as that
of the skull of the hare. But this is far from being the case; for the
average capacity of the two hare-skulls (Nos. 23, 24) is so much larger
than the average capacity of the seven lop-eared skulls, that the latter
would have to be increased 21 per cent to come up to the standard of the
hare. (4/23. This standard is apparently considerably too low, for Dr.
Crisp ('Proc. Zoolog. Soc.' 1861 page 86) gives 210 grains as the actual
weight of the brain of a hare which weighed 7 pounds, and 125 grains as the
weight of the brain of a rabbit which weighed 3 pounds 5 ounces, that is,
the same weight as the rabbit No. 1 in my list. Now the contents of the
skull of rabbit No. 1 in shot is in my table 972 grains; and according to
Dr. Crisp's ratio of 125 to 210, the skull of the hare ought to have
contained 1632 grains of shot, instead of only (in the largest hare in my
table) 1455 grains.)
I have previously remarked that, if we had possessed many domestic rabbits
of the same average size with the wild rabbit, it would have been easy to
compare the capacity of their skulls. Now the Himalayan, Moscow, and Angora
rabbits (Nos. 11, 12, 13 of Table 3) are only a little larger in body and
have skulls only a little longer, than the wild animal, and we see that the
actual capacity of their skulls is less than in the wild animal, and
considerably less by calculation (column 7), according to the difference in
the length of their skulls. The narrowness of the brain-case in these three
rabbits could be plainly seen and proved by external measurement. The
Chinchilla rabbit (No. 14) is a considerably larger animal than the wild
rabbit, yet the capacity of its skull only slightly exceeds that of the
wild rabbit. The Angora rabbit, No. 13, offers the most remarkable case;
this animal in its pure white colour and length of silky fur bears the
stamp of long domesticity. It has a considerably longer head and body than
the wild rabbit, but the actual capacity of its skull is less than that of
even the little wild Porto Santo rabbits. By the standard of the length of
skull the capacity (see column 7) is only half of what it ought to have
been! I kept this individual animal alive, and it was not unhealthy nor
idiotic. This case of the Angora rabbit so much surprised me, that I
repeated all the measurements and found them correct. I have also compared
the capacity of the skull of the Angora with that of the wild rabbit by
other standards, namely, by the length and weight of the body, and by the
weight of the limb-bones; but by all these standards the brain appears to
be much too small, though in a less degree when the standard of the limb-
bones was used; and this latter circumstance may probably be accounted for
by the limbs of this anciently domesticated breed having become much
reduced in weight, from its long-continued inactive life. Hence I infer
that in the Angora breed, which is said to differ from other breeds in
being quieter and more social, the capacity of the skull has really
undergone a remarkable amount of reduction.]
From the several facts above given,--namely, firstly, that the actual
capacity of the skull in the Himalayan, Moscow, and Angora breeds, is less
than in the wild rabbit, though they are in all their dimensions rather
larger animals; secondly, that the capacity of the skull of the large lop-
eared rabbits has not been increased in nearly the same ratio as the
capacity of the skull of the smaller wild rabbits has been decreased; and
thirdly, that the capacity of the skull in these same large lop-eared
rabbits is very inferior to that of the hare, an animal of nearly the same
size,--I conclude, notwithstanding the remarkable differences in capacity
in the skulls of the small Porto Santo rabbits, and likewise in the large
lop-eared kinds, that in all long-domesticated rabbits the brain has either
by no means increased in due proportion with the increased length of the
head and increased size of the body, or that it has actually decreased in
size, relatively to what would have occurred had these animals lived in a
state of nature. When we remember that rabbits, from having been
domesticated and closely confined during many generations, cannot have
exerted their intellect, instincts, senses, and voluntary movements, either
in escaping from various dangers or in searching for food, we may conclude
that their brains will have been feebly exercised, and consequently have
suffered in development. We thus see that the most important and
complicated organ in the whole organisation is subject to the law of
decrease in size from disuse.
Finally, let us sum up the more important modifications which domestic
rabbits have undergone, together with their causes as far as we can
obscurely see them. By the supply of abundant and nutritious food, together
with little exercise, and by the continued selection of the heaviest
individuals, the weight of the larger breeds has been more than doubled.
The bones of the limbs taken together have increased in weight, in due
proportion with the increased weight of body, but the hind legs have
increased less than the front legs; but in length they have not increased
in due proportion, and this may have been caused by the want of proper
exercise. With the increased size of the body the third cervical has
assumed characters proper to the fourth cervical vertebra; and the eighth
and ninth dorsal vertebrae have similarly assumed characters proper to the
tenth and posterior vertebrae. The skull in the larger breeds has increased
in length, but not in due proportion with the increased length of body; the
brain has not duly increased in dimensions, or has even actually decreased,
and consequently the bony case for the brain has remained narrow, and by
correlation has affected the bones of the face and the entire length of the
skull. The skull has thus acquired its characteristic narrowness. From
unknown causes the supra-orbital process of the frontal bones and the free
end of the malar bones have increased in breadth; and in the larger breeds
the occipital foramen is generally much less deeply notched than in wild
rabbits. Certain parts of the scapula and the terminal sternal bones have
become highly variable in shape. The ears have been increased enormously in
length and breadth through continued selection; their weight, conjoined
probably with the disuse of their muscles, has caused them to lop
downwards; and this has affected the position and form of the bony auditory
meatus; and this again, by correlation, the position in a slight degree of
almost every bone in the upper part of the skull, and even the position of
the condyles of the lower jaw.