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—VERtebræ—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[1] 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.[2]
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.[3] 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] Wild rabbits,
if taken young, can be domesticated, though the process is
generally very troublesome.[5] 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.[6] 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,[7] 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.[8] 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 mammæ 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 mammæ. 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.[9] 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.[10]
Illustration: Fig. 5—Half-lop Rabbit.
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,[11] “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;[12] 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[13] 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._[14] 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.[15] These rabbits breed perfectly true. A writer stated in
1857[16] 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[17] 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,[18] 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_[19] 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.”[20] 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.”[21] 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.[22] 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[23] 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.[24] 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.
Illustration: Fig. 6—Skull of Wild Rabbit. Fig. 7—Skull of large
Lop-eared Rabbit.
Illustration: Fig. 8—Part of Zygomatic Arch.
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, fig. 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 fig. 8; but
this circumstance mainly depends on the changed direction of the
meatus. The inter-parietal bone (see fig. 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”[25] of the occiput, instead of being truncated, or
projecting slightly as in the wild rabbit, is in most lop-eared
rabbits pointed, as in fig. 9, C. The paramastoids relatively to
the size of the skull are generally much thicker than in the wild
rabbit.
Illustration: Fig. 9—Posterior end of skull of Rabbits.
Illustration: Fig. 10—Occipital Foramen of Rabbits.
The occipital foramen (fig. 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.
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
fig. 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 (fig. 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!
Illustration: Fig. 11—Skull of Half-lop Rabbit.
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.
_Vertebræ._—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 vertebræ. This is remarkable, as
Gervais gives seven as the number for the whole genus Lepus. The caudal
vertebræ apparently differ by two or three, but I did not attend to
them, and they are difficult to count with certainty.
Illustration: Fig. 12—Atlas Vertebræ of Rabbits.
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 alæ are a little squarer in outline.
Illustration: Fig. 13—Third Cervical Vertebræ, of natural size, of—A.
Wild Rabbit; B. Hare-coloured, large, Lop-eared Rabbit.
_Third cervical vertebra._—In the wild rabbit (fig. 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 vertebræ 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.
Illustration: Fig. 14—Dorsal Vertebræ, 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 vertebræ._—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 vertebræ. In the large
lop-eared rabbits the neural spines of the tenth, ninth, and eighth
vertebræ, 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
vertebræ in some species of hares. In the Angora, Chinchilla, and
Himalayan rabbits, the neural spines of the eighth and ninth
vertebræ 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 vertebræ 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 fig. 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,[26] 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 vertebræ._—I have stated that in two cases there were eight
instead of seven lumbar vertebræ. The third lumbar vertebræ 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 hæmal spine.
Illustration: Fig. 15—Terminal bone of Sternum of Rabbits.
_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.
_Sternum._—The posterior end of the posterior sternal bone in the wild
rabbit (fig. 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.
Illustration: Fig. 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 (fig. 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
vertebræ of the wild and lop-eared rabbits, of which figures have been
given, had been found fossil, palæontologists 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.[27] 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.
I II III IV Name of Breed
WILD AND SEMI-WILD RABBITS. Length of
Skull. Length of
Body from
Incisors
to Anus. Weight
of whole
Body. Capacity
of Skull
measured
by Small
Shot. inches inches lbs ozs grains 1 Wild Rabbit,
Kent 3·15 17·4 3 5 972 2 Wild Rabbit,
Shetland Islands 3·15 — — 979 3 Wild Rabbit,
Ireland 3·15 — — 992 4 Domestic rabbit, run
wild, Sandon 3·15 18·5 — 997 5 Wild, common
variety, small specimen, Kent 2·96 17·0 2 14 875
6 Wild, fawn-coloured variety,
Scotland 3·10 — — 918 7 Silver-grey, small
specimen, Thetford warren 2·95 15·5 2 11 938
8 Feral rabbit, Porto Santo 2·83 — — 893
9 Feral rabbit, Porto Santo 2·85 — — 756
10 Feral Rabbit, Porto Santo 2·95 — — 835
Average of the three Porto Santo rabbits 2·88 — —
828
DOMESTIC RABBITS. 11 Himalayan 3·50 20·5 — 963
12 Moscow 3·25 17·0 3 8 803
13 Angora 3·50 19·5 3 1 697
14 Chinchilla 3·65 22·0 — 995 15 Large
lop-eared 4·10 24·5 7 0 1065 16 Large
lop-eared 4·10 25·0 7 13 1153 17 Large
lop-eared 4·07 — — 1037 18 Large
lop-eared 4·10 25·0 7 4 1208 19 Large
lop-eared 4·30 — — 1232 20 Large
lop-eared 4·25 — — 1124 21 Large
hare-coloured 3·86 24·0 6 14 1131 22 Average of
above seven large lop-eared rabbits 4·11 24·62 7
4 1136
23 Hare (_L. timidus_) English specimen 3·61 — 7
0 1315 24 Hare (_L. timidus_) German specimen 3·82 — 7
0 1415
V VI VII Name of Breed
WILD AND SEMI-WILD RABBITS. Capacity
calculated
according to
Length of Skull
relatively
to that of
No. 1. Difference
between
actual and
calculated
capacities
of Skulls. 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. grains grains 1 Wild Rabbit,
Kent — — 2 Wild Rabbit, Shetland
Islands — — 2 per cent. too heavy
in comparison with No. 1 3 Wild Rabbit, Ireland — —
4 Domestic rabbit, run wild, Sandon 5 Wild, common
variety, small specimen, Kent 913 38 4 per cent.
too light. 6 Wild, fawn-coloured variety, Scotland
950 32 3 per cent. too light. 7 Silver-grey, small
specimen, Thetford warren 910 28 3 per cent. too
heavy. 8 Feral rabbit, Porto Santo 873 20 2 per
cent. too heavy. 9 Feral rabbit, Porto Santo
879 123 16 per cent. too light. 10 Feral Rabbit, Porto
Santo 910 75 9 per cent. too light. Average of the
three Porto Santo rabbits 888 60 7 per cent. too
light.
DOMESTIC RABBITS. 11 Himalayan 1080 117 12 per cent.
too light. 12 Moscow 1002 199 24 per cent. too light.
13 Angora 1080 383 54 per cent. too light.
14 Chinchilla 1126 131 13 per cent. too light.
15 Large lop-eared 1265 200 18 per cent. too light.
16 Large lop-eared 1265 112 9 per cent. too light.
17 Large lop-eared 1255 218 21 per cent. too light.
18 Large lop-eared 1265 57 4 per cent. too light.
19 Large lop-eared 1326 94 7 per cent. too light.
20 Large lop-eared 1311 187 16 per cent. too light.
21 Large hare-coloured 1191 60 5 per cent. too
light. 22 Average of above seven large lop-eared
rabbits 1268 132 11 per cent. too light.
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.[28]
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 vertebræ have similarly
assumed characters proper to the tenth and posterior vertebræ. 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.
REFERENCES
[1] M. P. Gervais, ‘Hist. Nat. des Mammifères,’ 1854, tom. i., p. 288.
[2] U. Aldrovandi ‘De Quadrupedibus digitatis,’ 1637, p. 383. For
Confucius and G. Markham _see_ a writer who has studied the subject in
‘Cottage Gardener,’ Jan. 22, 1861, p. 250.
[3] Owen, ‘British Fossil Mammals,’ p. 212.
[4] Bechstein, ‘Naturgesch. Deutschlands,’ 1801, B. i. p. 1133. I have
received similar accounts with respect to England and Scotland.
[5] ‘Pigeons and Rabbits,’ by E. S. Delamer, 1854, p. 133. Sir J.
Sebright (‘Observations on Instinct,’ 1836, p. 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,’ tom. ii. p. 368.
[6] Gervais, ‘Hist. Nat. des Mammifères,’ tom. i. p. 292.
[7] _See_ Dr. P. Broca’s interesting memoir on this subject in
Brown-Séquard’s ‘Journ. de. Phys.,’ vol. ii. p. 367.
[8] The skulls of these breeds are briefly described in the ‘Journal
of Horticulture,’ May 7, 1861, p. 108.
[9] ‘Journal of Horticulture,’ 1861, p. 380.
[10] ‘Journal of Horticulture,’ May 28, 1861, p. 169.
[11] ‘Journal of Horticulture,’ 1861, p. 327. With respect to the ears
_see_ Delamer on ‘Pigeons and Rabbits,’ 1854, p. 141; also ‘Poultry
Chronicle,’ vol. ii. p. 499, and ditto for 1854, p. 586.
[12] Delamer, ‘Pigeons and Rabbits,’ p. 136. _See also_ ‘Journal of
Horticulture,’ 1861, p. 375.
[13] ‘An Account of the different Kinds of Sheep in the Russian
Dominions,’ 1794, p. 39.
[14] ‘Proc. Zoolog. Soc.,’ June 23, 1857, p. 159.
[15] ‘Journal of Horticulture,’ April 9, 1861, p. 35.
[16] ‘Cottage Gardener,’ 1857, p. 141.
[17] Mr. Bartlett, in ‘Proc. Zoolog Soc.,’ 1861, p. 40.
[18] ‘Phenomenon in Himalayan Rabbits,’ in ‘Journal of Horticulture,’
Jan. 27, 1865, p. 102.
[19] G. R. Waterhouse, ‘Natural History of Mammalia: Rodents,’ 1846,
pp. 52, 60, 105.
[20] Delamer on ‘Pigeons and Rabbits,’ p. 114.
[21] Gosse’s ‘Sojourn in Jamaica,’ 1851, p. 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’s ‘Travels,’ p. 407). In parts of India,
as I am informed by Mr. Blyth, they breed well.
[22] Darwin’s ‘Journal of Researches,’ p. 193; and ‘Zoology of the
Voyage of the Beagle: Mammalia,’ p. 92.
[23] Kerr’s ‘Collection of Voyages,’ vol. ii. p. 177: p. 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.
[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’Espèce,’ p. 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 élève en
domesticité.”
[25] Waterhouse, ‘Nat. Hist. Mammalia,’ vol. ii. p. 36.
[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.
[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.,’ Jan. 11, 1848, p. 8.
[28] This standard is apparently considerably too low, for Dr. Crisp
(‘Proc. Zoolog. Soc.,’ 1861, p. 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.