cautious in claiming to prove anything, but we think he has justified
his claim to have shown that telegony by no means always occurs, as many
breeders believe. His experiments so far support the view of Continental
mule-breeders that telegony, if it takes place, occurs very seldom. But
the experiments are not complete, and it is much to be hoped that they
may be continued. If it should subsequently appear that out of fifty
pure-bred foals from dams which have been previously mated with the
zebra no single instance of telegony be found, the doctrine may surely
be neglected by breeders; and if in the experiments which are now being
carried out with various other mammals and birds telegony does not
occur, the doctrine may be relegated to what the Americans would term
the ‘dumping-ground’ of old superstitions. The present state of the
matter may be summed up in the Professor’s own words: ‘The experiments,
as far as they have gone, afford no evidence in support of the telegony
hypothesis.’ Nothing has occurred which is not explicable on the theory
of reversion.
Partly owing to a certain doubt or distrust which has recently been
expressed as to the existence of reversion, and no doubt partly because
it is reasonable to hold that the phenomena of telegony may all be
referred to reversion, Professor Ewart has made some direct experiments
on this subject. Darwin, Tegetmeier, and many others have made numerous
breeding experiments on pigeons, with the result that we may say that
the crossing of extreme forms usually tends to reversion in the
offspring. The ancestor of the domestic pigeon is known with tolerable
certainty to have been the blue-rock pigeon, _Columba livia_. By
crossing a male barb-fantail and a female barb-spot Darwin produced a
bird ‘which was hardly distinguishable from the wild Shetland species’
of blue-rock. In his description of this experiment, Darwin, as Weismann
points out, confines himself chiefly to the coloration: he does not
inquire how far reversion also appears in the structure of the bird.
This question has been answered by one of Professor Ewart’s many
experiments with pigeons. He crossed a white fantail cock with the
offspring of an owl and an archangel. The fantail was pure white, with
thirty feathers in its tail, and was so prepotent as to produce white
offspring when mated with blue pouters. The owl-archangel was more of an
owl than an archangel. One of the young of this complex pair had the
coloration of the Shetland rock pigeon, which has a white croup and the
wings in front of the bars a uniform blue; the other resembled the
Indian rock pigeon in having a blue croup and the front part of the
wings chequered. In this second bird there was complete reversion as to
colour, and in the first, wherever measurements were possible, there
was practically complete reversion also as to form. ‘In its
measurements it is relatively almost identical with a typical Shetland
blue-rock.’ The tail feathers are twelve in number, and show but the
faintest indications of any colour-inheritance from their immediate
parents. An additional point of interest is that in disposition this
bird seems wilder and more shy than the domesticated breeds usually are.
It is vigorous and hardy, and is much admired by the fanciers.
Another bird whose wild ancestor is known with a high degree of
certainty is the barn-door fowl. It has sprung from the jungle fowl,
_Gallus bankiva_, and less remotely from the game fowl. Hence, if fowls
of different breeds are crossed, the offspring, should reversion occur,
ought to resemble either the jungle fowl or their less remote ancestors,
the game fowl. A dark red-breasted bantam was crossed with an Indian
game Dorking; of the nine chickens which resulted, six resembled
Dorkings, and three in both form and colour resembled game birds. Two of
the three grew up, and the only visible trace of their parentage was a
double comb inherited from their cross-bred father. Here again the
reversion does not stop at the colour and form, but extends to
disposition; the birds are very shy, and fly about like wild birds. The
above are but two instances out of many which might be quoted from the
Penycuik experiments; they are, however, unusually clear cases, and
should do something to restore confidence amongst recent doubters of
reversion.
An animal is said to be prepotent when it strongly impresses its own
peculiarities of form, colour, temperament, etc., on its offspring. In
the above-mentioned experiment with pigeons the owl had been prepotent
over the archangel in the mother of the offspring which showed such
marked reversion. There is no factor in breeding of more importance
than prepotency, and none which it is more difficult to estimate. The
term is necessarily a relative one, and, further, it may affect some
characters and not others. Often it must go undetected, as in the case
of the leader of a herd of wild cattle, who may be highly prepotent, but
whose prepotency, unless he is mated with members of another herd
displaying different characters, may pass unnoticed. Breeders claim to
be able to produce cattle so prepotent that they will produce their like
however mated. A well-known dealer in highly-bred ponies used to boast
that he had a filly so prepotent that, though she were sent to the best
Clydesdale stallion in Scotland, she would throw a colt showing no
cart-horse blood. Prepotency is usually obtained by inbreeding, which up
to a certain point fixes the character of a race, and in all cases tends
to check variation and reversion--the Jews, for instance, as a race are
strongly prepotent--but there is no doubt that it may also arise as a
sport, and this is probably its more usual origin in a state of nature.
Professor Ewart, however, believes that inbreeding is much commoner
among wild animals than has usually been conceded, and he holds the
opinion that the prepotency so induced has played a considerable part in
the origin of species. This, if true, would to some extent take the
place of Romanes’ ‘physiological selection’; for Romanes also thought
that, though of great importance, variation and natural selection were
insufficient to account for the origin of species without some factor
which would help to mitigate the swamping effect of intercrossing--some
such agency as the fences of modern farms and cattle-ranches--without
which the famous cattle breeds of the world would soon disappear in a
general ‘regression towards mediocrity.’
In inbreeding the great difficulty of the breeder is to know when to
stop. Carried too far it undoubtedly leads to degeneracy. In the
‘Domesticated Animals of Great Britain,’ Lowe records the case of a
gentleman who inbred foxhounds to such an extent that ‘the race actually
became monstrous and perished.’ Hogs, if too closely inbred, grow hair
instead of bristles; their legs become short and unable to support the
body; and not only is their fertility diminished, but the mothers cannot
nourish the young. That infertility is induced by inbreeding is further
shown by some experiments of Ritzema Bos with rats. From seven rats of
one family and an unrelated male he continued inbreeding for a period of
some six years, and bred about thirty generations. The average of the
numbers in each litter fell from 7½ in 1887 to 4-7/12 in 1891 and 3⅕ in
1892. Further, the offspring of inbred parents are usually weak. Sir
Everett Millais estimated that 60 to 70 per cent. of inbred dogs
attacked by distemper were carried off.
On the other hand, inbreeding often succeeds even when carried to what
the ordinary man would consider excess. The ‘Herd-book’ contains the
following case in point. The bull Bolingbroke and the cow Phœnix were
more closely related to one another than half-brother is to half-sister.
They were mated, and produced the bull Favourite. Favourite was then
coupled with his dam, and produced the cow Young Phœnix; he was then
coupled with his daughter Young Phœnix, and the world-famed Comet was
the result. Professor Ewart tells us that if there was little crossing
in the production of Comet, there was still less in that of Clarissa,
the mother of the celebrated Restless. An instance of the faith in close
inbreeding which exists in the minds of breeders occurred in a letter
which the _Field_ published in 1898, in which the writer stated he had
heard ‘Mr. Joseph Osborne, the ablest authority living on English
[Illustration: ROMULUS.]
[Illustration: MATOPO.
_To face page 92._]
thoroughbreds, declare that you cannot now get too much of Birdcatcher.’
So far as is known, no direct investigations have been made to test how
far inbreeding may be carried in the Equidæ; but, on the other hand, the
breeding of racehorses may perhaps be looked upon as a gigantic
experiment in this direction. Our English thoroughbreds can be traced
back to a few imported sires--the Byerly Turk, imported in 1689; the
Darley Arabian, in 1710; and the Godolphin Arabian, in 1730. Since then,
by careful breeding and nutrition, they have increased on an average
some 8 or 9 inches in height. There is, however, a widely-spread
impression that at present there is a marked deterioration in the
staying power and in the general ‘fitness’ of the racer. The falling off
is further shown by a fact commented on by Sir Walter Gilbey--viz., ‘the
smallness of the percentage of even tolerably successful horses out of a
prodigious number bred at an enormous outlay.’ In support of this he
quotes a sentence from the _Times_ (December 27, 1897), referring to a
sale in which thirty-two yearlings had been sold for 51,250 guineas.
‘These thirty-two yearlings’ (said the _Times_) ‘are represented by
two winners of five races, Florio Rubattino and La Reine, who have
contributed about £2,000 to the total cost; and there is not, so
far as can be known, a single one of the thirty others with any
prospect of making a racehorse.’
If, then, it is true that the English racehorse is on the down grade,
what steps should be taken to arrest this descent? Sir Everett Millais
restored a pack of basset hounds by crossing them with a bloodhound, the
original forefather of bassets. The resulting pups were bassets in form,
but not quite bassets in colour; when, however, these cross-breeds were
mated with bassets the majority of the pups turned out to be perfect
bassets both in shape and coloration. This indicates that one way to
rejuvenate the racehorse would be to have recourse to a new importation
of the best Arab mares that the plains of Arabia can produce. Breeders
hesitate to adopt this course, because their present breed is not only
larger, but, over very short distances, fleeter than its forefathers.
The shortening of the course in recent years is probably a further sign
of the degeneracy of our present racers. Were new blood introduced, and
more three-or four-mile races instituted, we should doubtless soon have
a return to the champion form of bygone days. Another method would be to
import some of the racers of Australia or New Zealand, and cross them
with the home product. Different surroundings, food, etc., soon
influence the constitution, and this being so, it would be advisable to
select those horses of pure descent which have been longest subjected to
these altered conditions. Thus the chance of reversion occurring would
be increased.
It has been noticed more than once in the preceding pages that a young
animal showing reversion is strong and vigorous. It is the belief of
dog-breeders that those members of an inbred litter which show reversion
are the strongest and best. Similarly, experience shows that if an
inbred sire and dam produce a dun-coloured striped foal it almost always
turns out well. Reversion is accompanied by a rejuvenescence; it is as
though the young animal had appeared at an earlier period in the
life-history of the race, before the race had undergone those changes in
the way of deterioration which so often accompany inbreeding.
Wild animals are frequently thought to be prepotent over tame ones, but
of the eleven zebra-hybrids bred at Penycuik only two took markedly
after their sire, the zebra Matopo.[2] There are other experiments
recounted which tell the other way, and at present this matter remains
in a state of considerable uncertainty. Further experiment may probably
show that though in most cases the oldest type is likely to prevail, the
offspring may take after the most inbred of its parents. The matter is
not altogether as simple as the above statements would imply. For
instance, a sport is often strongly prepotent. Standfuss’s experiments
in hybridizing butterflies tend to show this, and Mr. Galton even looks
upon prepotency as a sport or an aberrant variation. These butterfly
experiments also indicate that the male is usually prepotent over the
female; but so many questions of nutrition, the maturity of the
germ-cells, etc., enter into these intricate problems that it is
exceedingly difficult to disentangle the several factors which play a
part in the constitution of every living being.
Some years ago it used to be taught that species are infertile _inter
se_; nowadays it almost seems that we are giving up the idea of species
altogether. No two naturalists take precisely the same view of what
constitutes a species, and no one has succeeded in defining shortly and
clearly what a species is. The intersterility test has broken down; the
common goose and the Chinese goose, the common duck and the pintail
duck, various species of pheasant, the ox of Europe and the American
bison or the Indian zebu, not only breed together, but yield hybrids
which are themselves fertile; and the same is true of many plants. Why
the hybrids of Equidæ should prove sterile is not clear.
This article must not close without a word or two more about the
zebra-hybrids. It is mentioned above that only two out of the eleven
which have already been born took strongly after their father. This is
no proof that the wilder animal is not prepotent. Recent experiments in
hybridizing echinoderms, star-fish, seaurchins, etc., show that the
hybrid tends to resemble that species whose germ-cells are most nearly
approaching maturity; and thus the nutrition of the germ-cell is but
another thread in that complex tangle of heredity which must not be
overlooked in attempting to estimate the part played by prepotency and
reversion.
Those who have seen the young hybrids playing about in the fields at
Penycuik must agree that they are the most charming and compactly built
little animals possible; ‘_marvellous steeds, striped as a melon is, all
black and white_,’ as the poet has it. Of Romulus, the eldest of the
herd, Professor Ewart says:
‘When a few days old [he] was the most attractive little creature I
have ever seen. He seemed to combine all the grace and beauty of an
antelope and a well-bred Arab foal.... What has struck me from the
first has been his alertness and the expedition with which he
escapes from suspicious or unfamiliar objects. When quite young, if
caught napping in the paddock, the facility with which he, as it
were, rolled on to his feet and darted off was wonderful.’
The writer can fully confirm all the praise Professor Ewart lavishes on
his pets; in truth Romulus has been well described as a ‘bonnie colt
with rare quality of bone ... and with the dainty step and dignity of
the zebra.’ Remus, the offspring of the Irish mare, was from the first
more friendly than his half-brother; he objected less to the process of
weaning, and promised to be the handsomest and fleetest of the existing
hybrids.
On the whole the hybrids are unusually hardy; at the time of writing
only two have been lost--one, a twin, which died almost as soon as it
was born, and
[Illustration: ROMULUS.
_To face page 96._]
another which lived some three months and then succumbed. It is only
fair to say that the dam of the latter, who was only three years old
when the hybrid was born, had been much weakened by attacks of the
strongylus worm, and that she was the victim of close inbreeding. Both
the zebras and the hybrids which have been under observation at Penycuik
show a remarkable capacity for recovering from wounds. Accidental
injuries heal with great rapidity. On one occasion the surviving twin
was discovered with a flap of skin some five inches long hanging down
over the front of the left fetlock. The skin was stitched into its place
again, during which operation the little hybrid fought desperately, and
cried piteously; but it soon recovered, the wound healed, and now
scarcely a scar remains. There was no lameness and no swelling either at
the fetlock or above the knee. Some time ago four hybrid colts and three
ordinary foals were attacked by that scourge of the stable, the
strongylus worm. One of the latter died and another was reduced almost
to a skeleton: the hybrids, though obviously affected, suffered much
less than the others, and soon recovered. It is further noticeable that
the hybrids suffer less from colds and other slight ailments than the
mares and horses amongst which they live. Thus it seems that Colonel
Lugard’s hope has to some extent proved true. Some years ago, when
administering British East Africa, he strongly recommended the breeding
of zebra mules from both the horse and the donkey, believing that they
would prove exceptionally hardy and possibly impervious to the tsetse
fly. So far as Professor’s Ewart’s experiments go, the first part of the
forecast has proved correct. Unfortunately, the latter half has not been
justified.
The much dreaded tsetse fly, which has interfered so seriously with the
colonization of whole tracts of South Africa, is now known not to be
the direct cause of the disease which follows its puncture, but to be
the means by which the organism which causes the disease is introduced
into the body. In this respect the tsetse fly resembles the malarial
mosquito. It is not thought that the organism--a hæmatozoon--passes
through any of the stages of its life-history within the body of the
fly, but that the proboscis of that insect merely acts like an
inoculating needle. An answer to the important question, Are
zebra-hybrids fly-proof or not? has been attempted. Professor Ewart
generously allowed an experiment to be tried on two of his hybrids,
which were inoculated with the hæmatozoon, supplied from the
Pathological Laboratory at Cambridge. The result was unfortunate, for,
although the hybrids resisted the disease far longer than a mare which
was also inoculated as a control experiment, both ultimately succumbed.
There is no doubt that it is a comparatively easy matter to breed these
hybrids, and that they are not only extremely attractive animals to the
eye, but hardy and vigorous, possessed of great staying powers, and
promising to be capable of severe work. It is recognized that one of the
gravest difficulties which the Indian Army Corps has to contend with is
the paucity of mules, both for transport and mountain-battery work; and
at the time of the South African War a Commission was busily employed
purchasing mules both in Italy and in Texas, and elsewhere. Should these
hybrids turn out as well as they at present promise, they may fill a
want which is acutely felt by those responsible for the conduct of our
frequent ‘small wars,’ and, if bred largely in East Africa, may, as
Colonel Lugard suggested, prove a source of wealth and revenue in the
future.
We have hitherto said little or nothing about the book itself with which
we have been dealing. The larger part consists of three articles
reprinted from the _Veterinarian_ and one from the _Zoologist_; but the
more recent and more important half is the General Introduction,
covering a hundred pages, in which Professor Ewart sums up the results
of his experiments. The form of the work necessarily involves a good
deal of repetition, but in so complex a subject this is on the whole
rather an advantage than otherwise. Professor Ewart’s style is clear,
and his pages abound in apposite illustrations. The book cannot fail to
attract both the man of science and the practical breeder.
From what we have said it is evident that the Penycuik experiments are
of the highest interest both practical and theoretical, and the public
spirit and self-devotion shown by the Edinburgh professor in carrying
them out cannot be too widely recognized. The expense of feeding and
housing some thirty to forty horses, asses, and zebras is very great,
and the initial expenditure in erecting stables, buying land and fencing
it, is also considerable. It is, perhaps, not too much to hope that some
public body may be willing to undertake at least a part of the burden.
The Zoological Society of London possesses, not only the necessary
establishment required, including a well-trained staff, but it also has
facilities for obtaining all kinds of animals which are far greater than
those of any private individual. We hope that the day is not far distant
when experiments of this kind will be systematically carried on under
the direction of the authorities who control the Gardens in Regent’s
Park. Probably such experiments would have better prospects of success
at a farm in the country than in London, and there is much to be said
for such an experimental farm under the management of a body like the
Zoological Society. Apart from the more strictly scientific use to which
it might be put, it would serve as a convenient sanatorium for those
animals which cannot stand the fogs and damp of London.
PASTEUR
_Je suis chimiste, je fais des expériences et je tâche de comprendre ce
qu’elles disent._--PASTEUR.
As one walks down the Rue des Tanneurs, in the small provincial town of
Dôle, where the main line from Paris to Pontarlier sends off a branch
north-east towards Besançon, a small tablet set in the _façade_ of a
humble dwelling catches the eye. It bears the following inscription in
gilt letters: ‘Ici est né Louis Pasteur le 27 décembre 1822.’
Pasteur came of the people. In the heraldic meaning of the term, he was
emphatically not ‘born.’ His forbears were shepherds, peasants, tillers
of the earth, millers, and latterly, tanners. But he came from amongst
the best peasantry in Europe, that peasantry which is still the backbone
of the great French nation. The admirable care with which records are
preserved in France has enabled Pasteur’s son-in-law and latest
biographer to trace the family name in the parish archives back to the
beginning of the seventeenth century, at which period numerous Pasteurs
were living in the villages round about the Priory of Mouthe, ‘en pleine
Franche-Comté.’
The first to emerge clearly from the confused cluster of possible
ancestors is a certain Denis Pasteur, who became miller to the Comte
d’Udressier, after whom he doubtless named his son Claude, born in 1683.
Claude in his turn became a miller, and died in the year 1746. Of his
eight children, the youngest, Claude-Étienne, was the great-grandfather
of Louis Pasteur. The inhabitants of Franche-Comté were, in large part,
serfs--‘gens de mainmorte,’ as they termed them then. Claude-Étienne,
being a serf, at the age of thirty wished to enfranchise himself; and
this he did in 1763, by the special grace of ‘Messire
Philippe-Marie-Francois, Comte d’Udressier, Seigneur d’Ecleux, Cramans,
Lemuy, et autres lieux,’ and on the payment of four _louis-d’or_. He
subsequently married and had children. His third son, Jean-Henri, who
for a time carried on his father’s trade of tanner at Besançon, seems to
have disappeared at the age of twenty-seven, leaving a small boy,
Jean-Joseph Pasteur, born in 1791, who was brought up by his grandmother
and his father’s sister.