CHAPTER 2.XIII.

INHERITANCE continued--REVERSION OR ATAVISM.

DIFFERENT FORMS OF REVERSION.

IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, FOWLS, HORNLESS CATTLE AND SHEEP,

IN CULTIVATED PLANTS.

REVERSION IN FERAL ANIMALS AND PLANTS.

REVERSION IN CROSSED VARIETIES AND SPECIES.

REVERSION THROUGH BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR

FRUIT.

IN DIFFERENT PARTS OF THE BODY IN THE SAME ANIMAL.

THE ACT OF CROSSING A DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH

INSTINCTS.

OTHER PROXIMATE CAUSES OF REVERSION.

LATENT CHARACTERS.

SECONDARY SEXUAL CHARACTERS.

UNEQUAL DEVELOPMENT OF THE TWO SIDES OF THE BODY.

APPEARANCE WITH ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS.

THE GERM, WITH ALL ITS LATENT CHARACTERS, A WONDERFUL OBJECT.

MONSTROSITIES.

PELORIC FLOWERS DUE IN SOME CASES TO REVERSION.

The great principle of inheritance to be discussed in this chapter has been

recognised by agriculturists and authors of various nations, as shown by the

scientific term ATAVISM, derived from atavus, an ancestor; by the English

terms of REVERSION, or THROWING-BACK; by the French PAS-EN-ARRIERE; and by the

German RUCKSCHLAG, or RUCKSCHRITT. When the child resembles either grandparent

more closely than its immediate parents, our attention is not much arrested,

though in truth the fact is highly remarkable; but when the child resembles

some remote ancestor or some distant member in a collateral line,--and in the

last case we must attribute this to the descent of all the members from a

common progenitor,--we feel a just degree of astonishment. When one parent

alone displays some newly-acquired and generally inheritable character, and

the offspring do not inherit it, the cause may lie in the other parent having

the power of prepotent transmission. But when both parents are similarly

characterised, and the child does not, whatever the cause may be, inherit the

character in question, but resembles its grandparents, we have one of the

simplest cases of reversion. We continually see another and even more simple

case of atavism, though not generally included under this head, namely, when

the son more closely resembles his maternal than his paternal grand-sire in

some male attribute, as in any peculiarity in the beard of man, the horns of

the bull, the hackles or comb of the cock, or, as in certain diseases

necessarily confined to the male sex; for as the mother cannot possess or

exhibit such male attributes, the child must inherit them, through her blood,

from his maternal grandsire.

The cases of reversion may be divided into two main classes which, however, in

some instances, blend into one another; namely, first, those occurring in a

variety or race which has not been crossed, but has lost by variation some

character that it formerly possessed, and which afterwards reappears. The

second class includes all cases in which an individual with some

distinguishable character, a race, or species, has at some former period been

crossed, and a character derived from this cross, after having disappeared

during one or several generations, suddenly reappears. A third class,

differing only in the manner of reproduction, might be formed to include all

cases of reversion effected by means of buds, and therefore independent of

true or seminal generation. Perhaps even a fourth class might be instituted,

to include reversions by segments in the same individual flower or fruit, and

in different parts of the body in the same individual animal as it grows old.

But the two first main classes will be sufficient for our purpose.

REVERSION TO LOST CHARACTERS BY PURE OR UNCROSSED FORMS.

Striking instances of this first class of cases were given in the sixth

chapter, namely, of the occasional reappearance, in variously-coloured breeds

of the pigeon, of blue birds with all the marks characteristic of the wild

Columba livia. Similar cases were given in the case of the fowl. With the

common ass, as the legs of the wild progenitor are almost always striped, we

may feel assured that the occasional appearance of such stripes in the

domestic animal is a case of simple reversion. But I shall be compelled to

refer again to these cases, and therefore here pass them over.

The aboriginal species from which our domesticated cattle and sheep are

descended, no doubt possessed horns; but several hornless breeds are now well

established. Yet in these--for instance, in Southdown sheep--"it is not

unusual to find among the male lambs some with small horns." The horns, which

thus occasionally reappear in other polled breeds, either "grow to the full

size," or are curiously attached to the skin alone and hang "loosely down, or

drop off." (13/1. 'Youatt on Sheep' pages 20, 234. The same fact of loose

horns occasionally appearing in hornless breeds has been observed in Germany;

Bechstein 'Naturgesch. Deutschlands.' b. 1 s. 362.) The Galloways and Suffolk

cattle have been hornless for the last 100 or 150 years, but a horned calf,

with the horn often loosely attached, is occasionally produced. (13/2. 'Youatt

on Cattle' pages 155, 174.)

There is reason to believe that sheep in their early domesticated condition

were "brown or dingy black;" but even in the time of David certain flocks were

spoken of as white as snow. During the classical period the sheep of Spain are

described by several ancient authors as being black, red, or tawny. (13/3.

'Youatt on Sheep' 1838 pages 17, 145.) At the present day, notwithstanding the

great care which is taken to prevent it, particoloured lambs and some entirely

black are occasionally, or even frequently, dropped by our most highly

improved and valued breeds, such as the Southdowns. Since the time of the

famous Bakewell, during the last century, the Leicester sheep have been bred

with the most scrupulous care; yet occasionally grey-faced, or black-spotted,

or wholly black lambs appear. (13/4. I have been informed of this fact through

the Rev. W.D. Fox on the excellent authority of Mr. Wilmot: see also remarks

on this subject in an article in the 'Quarterly Review' 1849 page 395.) This

occurs still more frequently with the less improved breeds, such as the

Norfolks. (13/5. Youatt pages 19, 234.) As bearing on this tendency in sheep

to revert to dark colours, I may state (though in doing so I trench on the

reversion of crossed breeds, and likewise on the subject of prepotency) that

the Rev. W.D. Fox was informed that seven white Southdown ewes were put to a

so-called Spanish ram, which had two small black spots on his sides, and they

produced thirteen lambs, all perfectly black. Mr. Fox believes that this ram

belonged to a breed which he has himself kept, and which is always spotted

with black and white; and he finds that Leicester sheep crossed by rams of

this breed always produce black lambs: he has gone on recrossing these crossed

sheep with pure white Leicesters during three successive generations, but

always with the same result. Mr. Fox was also told by the friend from whom the

spotted breed was procured, that he likewise had gone on for six or seven

generations crossing with white sheep, but still black lambs were invariably

produced.

Similar facts could be given with respect to tailless breeds of various

animals. For instance, Mr. Hewitt (13/6. 'The Poultry Book' by Mr. Tegetmeier

1866 page 231.) states that chickens bred from some rumpless fowls, which were

reckoned so good that they won a prize at an exhibition, "in a considerable

number of instances were furnished with fully developed tail-feathers." On

inquiry, the original breeder of these fowls stated that, from the time when

he had first kept them, they had often produced fowls furnished with tails;

but that these latter would again reproduce rumpless chickens.

Analogous cases of reversion occur in the vegetable kingdom; thus "from seeds

gathered from the finest cultivated varieties of Heartsease (Viola tricolor),

plants perfectly wild both in their foliage and their flowers are frequently

produced;" (13/7. Loudon's 'Gardener's Mag.' volume 10 1834 page 396: a

nurseryman, with much experience on this subject, has likewise assured me that

this sometimes occurs.) but the reversion in this instance is not to a very

ancient period, for the best existing varieties of the heartsease are of

comparatively modern origin. With most of our cultivated vegetables there is

some tendency to reversion to what is known to be, or may be presumed to be,

their aboriginal state; and this would be more evident if gardeners did not

generally look over their beds of seedlings, and pull up the false plants or

"rogues" as they are called. It has already been remarked, that some few

seedling apples and pears generally resemble, but apparently are not identical

with, the wild trees from which they are descended. In our turnip (13/8.

'Gardener's Chronicle' 1855 page 777.) and carrot-beds a few plants often

"break "--that is, flower too soon; and their roots are generally hard and

stringy, as in the parent-species. By the aid of a little selection, carried

on during a few generations, most of our cultivated plants could probably be

brought back, without any great change in their conditions of life, to a wild

or nearly wild condition: Mr. Buckman has effected this with the parsnip

(13/9. Ibid 1862 page 721.); and Mr. Hewett C. Watson, as he informs me,

selected, during three generations, "the most diverging plants of Scotch kail,

perhaps one of the least modified varieties of the cabbage; and in the third

generation some of the plants came very close to the forms now established in

England about old castle-walls, and called indigenous."

REVERSION IN ANIMALS AND PLANTS WHICH HAVE RUN WILD.

In the cases hitherto considered, the reverting animals and plants have not

been exposed to any great or abrupt change in their conditions of life which

could have induced this tendency; but it is very different with animals and

plants which have become feral or run wild. It has been repeatedly asserted in

the most positive manner by various authors, that feral animals and plants

invariably return to their primitive specific type. It is curious on what

little evidence this belief rests. Many of our domesticated animals could not

subsist in a wild state; thus, the more highly improved breeds of the pigeon

will not "field" or search for their own food. Sheep have never become feral,

and would be destroyed by almost every beast of prey. (13/10. Mr. Boner speaks

('Chamois-hunting' 2nd edition 1860 page 92) of sheep often running wild in

the Bavarian Alps; but, on making further inquiries at my request, he found

that they are not able to establish themselves; they generally perish from the

frozen snow clinging to their wool, and they have lost the skill necessary to

pass over steep icy slopes. On one occasion two ewes survived the winter, but

their lambs perished.) In several cases we do not know the aboriginal parent-

species, and cannot possibly tell whether or not there has been any close

degree of reversion. It is not known in any instance what variety was first

turned out; several varieties have probably in some cases run wild, and their

crossing alone would tend to obliterate their proper character. Our

domesticated animals and plants, when they run wild, must always be exposed to

new conditions of life, for, as Mr. Wallace (13/11. See some excellent remarks

on this subject by Mr. Wallace 'Journal Proc. Linn. Soc.' 1858 volume 3 page

60.) has well remarked, they have to obtain their own food, and are exposed to

competition with the native productions. Under these circumstances, if our

domesticated animals did not undergo change of some kind, the result would be

quite opposed to the conclusions arrived at in this work. Nevertheless, I do

not doubt that the simple fact of animals and plants becoming feral, does

cause some tendency to reversion to the primitive state; though this tendency

has been much exaggerated by some authors.

[I will briefly run through the recorded cases. With neither horses nor cattle

is the primitive stock known; and it has been shown in former chapters that

they have assumed different colours in different countries. Thus the horses

which have run wild in South America are generally brownish-bay, and in the

East dun-coloured; their heads have become larger and coarser, and this may be

due to reversion. No careful description has been given of the feral goat.

Dogs which have run wild in various countries have hardly anywhere assumed a

uniform character; but they are probably descended from several domestic

races, and aboriginally from several distinct species. Feral cats, both in

Europe and La Plata, are regularly striped; in some cases they have grown to

an unusually large size, but do not differ from the domestic animal in any

other character. When variously-coloured tame rabbits are turned out in

Europe, they generally reacquire the colouring of the wild animal; there can

be no doubt that this does really occur, but we should remember that oddly-

coloured and conspicuous animals would suffer much from beasts of prey and

from being easily shot; this at least was the opinion of a gentleman who tried

to stock his woods with a nearly white variety; if thus destroyed, they would

be supplanted by, instead of being transformed into, the common rabbit. We

have seen that the feral rabbits of Jamaica, and especially of Porto Santo,

have assumed new colours and other new characters. The best known case of

reversion, and that on which the widely spread belief in its universality

apparently rests, is that of pigs. These animals have run wild in the West

Indies, South America, and the Falkland Islands, and have everywhere acquired

the dark colour, the thick bristles, and great tusks of the wild boar; and the

young have reacquired longitudinal stripes. But even in the case of the pig,

Roulin describes the half-wild animals in different parts of South America as

differing in several respects. In Louisiana the pig (13/12. Dureau de la Malle

'Comptes Rendus' tome 41 1855 page 807. From the statements above given, the

author concludes that the wild pigs of Louisiana are not descended from the

European Sus scrofa.) has run wild, and is said to differ a little in form,

and much in colour, from the domestic animal, yet does not closely resemble

the wild boar of Europe. With pigeons and fowls (13/13. Capt. W. Allen, in his

'Expedition to the Niger' states that fowls have run wild on the island of

Annobon, and have become modified in form and voice. The account is so meagre

and vague that it did not appear to me worth copying; but I now find that

Dureau de la Malle ('Comptes Rendus' tome 41 1855 page 690) advances this as a

good instance of reversion to the primitive stock, and as confirmatory of a

still more vague statement in classical times by Varro.), it is not known what

variety was first turned out, nor what character the feral birds have assumed.

The guinea-fowl in the West Indies, when feral, seems to vary more than in the

domesticated state.

With respect to plants run wild, Dr. Hooker (13/14. 'Flora of Australia' 1859

Introduction page 9.) has strongly insisted on what slight evidence the common

belief in their reversion to a primitive state rests. Godron (13/15. 'De

l'Espece' tome 2 pages 54, 58, 60.) describes wild turnips, carrots, and

celery; but these plants in their cultivated state hardly differ from their

wild prototypes, except in the succulency and enlargement of certain parts,--

characters which would certainly be lost by plants growing in poor soil and

struggling with other plants. No cultivated plant has run wild on so enormous

a scale as the cardoon (Cynara cardunculus) in La Plata. Every botanist who

has seen it growing there, in vast beds, as high as a horse's back, has been

struck with its peculiar appearance; but whether it differs in any important

point from the cultivated Spanish form, which is said not to be prickly like

its American descendant, or whether it differs from the wild Mediterranean

species, which is said not to be social (though this may be due merely to the

nature of the conditions), I do not know.]

REVERSION TO CHARACTERS DERIVED FROM A CROSS, IN THE CASE OF SUB-VARIETIES,

RACES, AND SPECIES.

When an individual having some recognisable peculiarity unites with another of

the same sub-variety, not having the peculiarity in question, it often

reappears in the descendants after an interval of several generations. Every

one must have noticed, or heard from old people of children closely resembling

in appearance or mental disposition, or in so small and complex a character as

expression, one of their grandparents, or some more distant collateral

relation. Very many anomalies of structure and diseases (13/16. Mr. Sedgwick

gives many instances in the 'British and Foreign Med.-Chirurg. Review' April

and July 1863 pages 448, 188.) of which instances have been given in the last

chapter, have come into a family from one parent, and have reappeared in the

progeny after passing over two or three generations. The following case has

been communicated to me on good authority, and may, I believe, be fully

trusted: a pointer-bitch produced seven puppies; four were marked with blue

and white, which is so unusual a colour with pointers that she was thought to

have played false with one of the greyhounds, and the whole litter was

condemned; but the gamekeeper was permitted to save one as a curiosity. Two

years afterwards a friend of the owner saw the young dog, and declared that he

was the image of his old pointer-bitch Sappho, the only blue and white pointer

of pure descent which he had ever seen. This led to close inquiry, and it was

proved that he was the great-great-grandson of Sappho; so that, according to

the common expression, he had only 1/16th of her blood in his veins. I may

give one other instance, on the authority of Mr. R. Walker, a large cattle-

breeder in Kincardineshire. He bought a black bull, the son of a black cow

with white legs, white belly and part of the tail white; and in 1870 a calf

the gr.-gr.-gr.-gr.-grandchild of this cow was born coloured in the same very

peculiar manner; all the intermediate offspring having been black. In these

cases there can hardly be a doubt that a character derived from a cross with

an individual of the same variety reappeared after passing over three

generations in the one case, and five in the other.

When two distinct races are crossed, it is notorious that the tendency in the

offspring to revert to one or both parent-forms is strong, and endures for

many generations. I have myself seen the clearest evidence of this in crossed

pigeons and with various plants. Mr. Sidney (13/17. In his edition of 'Youatt

on the Pig' 1860 page 27.) states that, in a litter of Essex pigs, two young

ones appeared which were the image of the Berkshire boar that had been used

twenty-eight years before in giving size and constitution to the breed. I

observed in the farmyard at Betley Hall some fowls showing a strong likeness

to the Malay breed, and was told by Mr. Tollet that he had forty years before

crossed his birds with Malays; and that, though he had at first attempted to

get rid of this strain, he had subsequently given up the attempt in despair,

as the Malay character would reappear.

This strong tendency in crossed breeds to revert has given rise to endless

discussions in how many generations after a single cross, either with a

distinct breed or merely with an inferior animal, the breed may be considered

as pure, and free from all danger of reversion. No one supposes that less than

three generations suffices, and most breeders think that six, seven, or eight

are necessary, and some go to still greater lengths. (13/18. Dr. P. Lucas,

'Hered. Nat.' tome 2 pages 314, 892: see a good practical article on the

subject in 'Gardener's Chronicle' 1856 page 620. I could add a vast number of

references, but they would be superfluous.) But neither in the case of a breed

which has been contaminated by a single cross, nor when, in the attempt to

form an intermediate breed, half-bred animals have been matched together

during many generations, can any rule be laid down how soon the tendency to

reversion will be obliterated. It depends on the difference in the strength or

prepotency of transmission in the two parent-forms, on their actual amount of

difference, and on the nature of the conditions of life to which the crossed

offspring are exposed. But we must be careful not to confound these cases of

reversion to characters which were gained by a cross, with those under the

first class, in which characters originally common to BOTH parents, but lost

at some former period, reappear; for such characters may recur after an almost

indefinite number of generations.

The law of reversion is as powerful with hybrids, when they are sufficiently

fertile to breed together, or when they are repeatedly crossed with either

pure parent-form, as in the case of mongrels. It is not necessary to give

instances. With plants almost every one who has worked on this subject, from

the time of Kolreuter to the present day, has insisted on this tendency.

Gartner has recorded some good instances; but no one has given more striking

ones than Naudin. (13/19. Kolreuter gives curious cases in his 'Dritte

Fortsetzung' 1766 ss. 53, 59; and in his well-known 'Memoirs on Lavatera and

Jalapa.' Gartner 'Bastarderzeugung' ss. 437, 441, etc. Naudin in his

"Recherches sur l'Hybridite" 'Nouvelles Archives du Museum' tome 1 page 25.)

The tendency differs in degree or strength in different groups, and partly

depends, as we shall presently see, on whether the parent-plants have been

long cultivated. Although the tendency to reversion is extremely general with

nearly all mongrels and hybrids, it cannot be considered as invariably

characteristic of them; it may also be mastered by long-continued selection;

but these subjects will more properly be discussed in a future chapter on

Crossing. From what we see of the power and scope of reversion, both in pure

races, and when varieties or species are crossed, we may infer that characters

of almost every kind are capable of reappearing after having been lost for a

great length of time. But it does not follow from this that in each particular

case certain characters will reappear; for instance, this will not occur when

a race is crossed with another endowed with prepotency of transmission.

Sometimes the power of reversion wholly fails, without our being able to

assign any cause for the failure: thus it has been stated that in a French

family in which 85 out of above 600 members, during six generations, had been

subject to night-blindness, "there has not been a single example of this

affection in the children of parents who were themselves free from it."

(13/20. Quoted by Mr. Sedgwick in 'Med.-Chirurg. Review' April 1861 page 485.

Dr. H. Dobell in 'Med.-Chirurg. Transactions' volume 46 gives an analogous

case in which, in a large family, fingers with thickened joints were

transmitted to several members during five generations; but when the blemish

once disappeared it never reappeared.)

REVERSION THROUGH BUD-PROPAGATION--PARTIAL REVERSION, BY SEGMENTS IN THE SAME

FLOWER OR FRUIT, OR IN DIFFERENT PARTS OF THE BODY IN THE SAME INDIVIDUAL

ANIMAL.

In the eleventh chapter many cases of reversion by buds, independently of

seminal generation, were given--as when a leaf-bud on a variegated, a curled,

or laciniated variety suddenly reassumes its proper character; or as when a

Provence-rose appears on a moss-rose, or a peach on a nectarine-tree. In some

of these cases only half the flower or fruit, or a smaller segment, or mere

stripes, reassume their former character; and here we have reversion by

segments. Vilmorin (13/21. Verlot 'Des Varietes' 1865 page 63.) has also

recorded several cases with plants derived from seed, of flowers reverting by

stripes or blotches to their primitive colours: he states that in all such

cases a white or pale-coloured variety must first be formed, and, when this is

propagated for a length of time by seed, striped seedlings occasionally make

their appearance; and these can afterwards by care be multiplied by seed.

The stripes and segments just referred to are not due, as far as is known, to

reversion to characters derived from a cross, but to characters lost by

variation. These cases, however, as Naudin (13/22. 'Nouvelles Archives du

Museum' tome 1 page 25. Alex. Braun (in his 'Rejuvenescence' Ray Soc. 1853

page 315) apparently holds a similar opinion.) insists in his discussion on

disjunction of character, are closely analogous with those given in the

eleventh chapter, in which crossed plants have been known to produce half-and-

half or striped flowers and fruit, or distinct kinds of flowers on the same

root resembling the two parent-forms. Many piebald animals probably come under

this same head. Such cases, as we shall see in the chapter on Crossing,

apparently result from certain characters not readily blending together, and,

as a consequence of this incapacity for fusion, the offspring either perfectly

resemble one of their two parents, or resemble one parent in one part, and the

other parent in another part; or whilst young are intermediate in character,

but with advancing age revert wholly or by segments to either parent-form, or

to both. Thus, young trees of the Cytisus adami are intermediate in foliage

and flowers between the two parent-forms; but when older the buds continually

revert either partially or wholly to both forms. The cases given in the

eleventh chapter on the changes which occurred during growth in crossed plants

of Tropaeolum, Cereus, Datura, and Lathyrus are all analogous. As, however,

these plants are hybrids of the first generation, and as their buds after a

time come to resemble their parents and not their grandparents, these cases do

not at first appear to come under the law of reversion in the ordinary sense

of the word; nevertheless, as the change is effected through a succession of

bud-generations on the same plant, they may be thus included.

Analogous facts have been observed in the animal kingdom, and are more

remarkable, as they occur in the same individual in the strictest sense, and

not as with plants through a succession of bud-generations. With animals the

act of reversion, if it can be so designated, does not pass over a true

generation, but merely over the early stages of growth in the same individual.

For instance, I crossed several white hens with a black cock, and many of the

chickens were, during the first year, perfectly white, but acquired during the

second year black feathers; on the other hand, some of the chickens which were

at first black, became during the second year piebald with white. A great

breeder (13/23. Mr. Teebay in 'The Poultry Book' by Mr. Tegetmeier 1866 page

72.) says, that a Pencilled Brahma hen which has any of the blood of the Light

Brahma in her, will "occasionally produce a pullet well pencilled during the

first year, but she will most likely moult brown on the shoulders and become

quite unlike her original colours in the second year." The same thing occurs

with light Brahmas if of impure blood. I have observed exactly similar cases

with the crossed offspring from differently coloured pigeons. But here is a

more remarkable fact: I crossed a turbit, which has a frill formed by the

feathers being reversed on its breast, with a trumpeter; and one of the young

pigeons thus raised at first showed not a trace of the frill, but, after

moulting thrice, a small yet unmistakably distinct frill appeared on its

breast. According to Girou (13/24. Quoted by Hofacker 'Ueber die

Eigenschaften' etc. s. 98.) calves produced from a red cow by a black bull, or

from a black cow by a red bull, are not rarely born red, and subsequently

become black. I possess a dog, the daughter of a white terrier by a fox-

coloured bulldog; as a puppy she was quite white, but when about six months

old a black spot appeared on her nose, and brown spots on her ears. When a

little older she was badly wounded on the back, and the hair which grew on the

cicatrix was of a brown colour, apparently derived from her father. This is

the more remarkable, as with most animals having coloured hair, that which

grows on a wounded surface is white.

In the foregoing cases, the characters which with advancing age reappeared,

were present in the immediately preceding generations; but characters

sometimes reappear in the same manner after a much longer interval of time.

Thus the calves of a hornless race of cattle which originated in Corrientes,

though at first quite hornless, as they become adult sometimes acquire small,

crooked, and loose horns; and these in succeeding years occasionally become

attached to the skull. (13/25. Azara 'Essais Hist. Nat. de Paraguay' tome 2

1801 page 372.) White and black Bantams, both of which generally breed true,

sometimes assume as they grow old a saffron or red plumage. For instance, a

first-rate black bantam has been described, which during three seasons was

perfectly black, but then annually became more and more red; and it deserves

notice that this tendency to change, whenever it occurs in a bantam, "is

almost certain to prove hereditary." (13/26. These facts are given on the high

authority of Mr. Hewitt in 'The Poultry Book' by Mr. Tegetmeier 1866 page

248.) The cuckoo or blue-mottled Dorking cock, when old, is liable to acquire

yellow or orange hackles in place of his proper bluish-grey hackles. (13/27.

'The Poultry Book' by Tegetmeier 1866 page 97.) Now as Gallus bankiva is

coloured red and orange, and as Dorking fowls and bantams are descended from

this species, we can hardly doubt that the change which occasionally occurs in

the plumage of these birds as their age advances, results from a tendency in

the individual to revert to the primitive type.

CROSSING AS A DIRECT CAUSE OF REVERSION.

It has long been notorious that hybrids and mongrels often revert to both or

to one of their parent-forms, after an interval of from two to seven or eight,

or, according to some authorities, even a greater number of generations. But

that the act of crossing in itself gives an impulse towards reversion, as

shown by the reappearance of long-lost characters, has never, I believe, been

hitherto proved. The proof lies in certain peculiarities, which do not

characterise the immediate parents, and therefore cannot have been derived

from them, frequently appearing in the offspring of two breeds when crossed,

which peculiarities never appear, or appear with extreme rarity, in these same

breeds, as long as they are precluded from crossing. As this conclusion seems

to me highly curious and novel, I will give the evidence in detail.

[My attention was first called to this subject, and I was led to make numerous

experiments, by MM. Boitard and Corbie having stated that, when they crossed

certain breeds of pigeons, birds coloured like the wild C. livia, or the

common dovecote--namely, slaty-blue, with double black wing-bars, sometimes

chequered with black, white loins, the tail barred with black, with the outer

feathers edged with white,--were almost invariably produced. The breeds which

I crossed, and the remarkable results attained, have been fully described in

the sixth chapter. I selected pigeons belonging to true and ancient breeds,

which had not a trace of blue or any of the above specified marks; but when

crossed, and their mongrels recrossed, young birds were often produced, more

or less plainly coloured slaty-blue, with some or all of the proper

characteristic marks. I may recall to the reader's memory one case, namely,

that of a pigeon, hardly distinguishable from the wild Shetland species, the

grandchild of a red-spot, white fantail, and two black barbs, from any of

which, when purely-bred, the production of a pigeon coloured like the wild C.

livia would have been almost a prodigy.

I was thus led to make the experiments, recorded in the seventh chapter, on

fowls. I selected long-established pure breeds, in which there was not a trace

of red, yet in several of the mongrels feathers of this colour appeared; and

one magnificent bird, the offspring of a black Spanish cock and white Silk

hen, was coloured almost exactly like the wild Gallus bankiva. All who know

anything of the breeding of poultry will admit that tens of thousands of pure

Spanish and of pure white Silk fowls might have been reared without the

appearance of a red feather. The fact, given on the authority of Mr.

Tegetmeier, of the frequent appearance, in mongrel fowls, of pencilled or

transversely-barred feathers, like those common to many gallinaceous birds, is

likewise apparently a case of reversion to a character formerly possessed by

some ancient progenitor of the family. I owe to the kindness of this excellent

observer the opportunity of inspecting some neck-hackles and tail-feathers

from a hybrid between the common fowl and a very distinct species, the Gallus

varius; and these feathers are transversely striped in a conspicuous manner

with dark metallic blue and grey, a character which could not have been

derived from either immediate parent.

I have been informed by Mr. B.P. Brent, that he crossed a white Aylesbury

drake and a black so-called Labrador duck, both of which are true breeds, and

he obtained a young drake closely like the mallard (A. boschas). Of the musk-

duck (Cairina moschata, Linn.) there are two sub-breeds, namely, white and

slate-coloured; and these I am informed breed true, or nearly true. But the

Rev. W.D. Fox tells me that, by putting a white drake to a slate-coloured

duck, black birds, pied with white, like the wild musk-duck, were always

produced. I hear from Mr. Blyth that hybrids from the canary and gold-finch

almost always have streaked feathers on their backs; and this streaking must

be derived from the original wild canary.

We have seen in the fourth chapter, that the so-called Himalayan rabbit, with

its snow-white body, black ears, nose, tail, and feet, breeds perfectly true.

This race is known to have been formed by the union of two varieties of

silver-grey rabbits. Now, when a Himalayan doe was crossed by a sandy-coloured

buck, a silver-grey rabbit was produced; and this is evidently a case of

reversion to one of the parent varieties. The young of the Himalayan rabbit

are born snow-white, and the dark marks do not appear until some time

subsequently; but occasionally young Himalayan rabbits are born of a light

silver-grey, which colour soon disappears; so that here we have a trace of

reversion, during an early period of life, to the parent varieties,

independently of any recent cross.

In the third chapter it was shown that at an ancient period some breeds of

cattle in the wilder parts of Britain were white with dark ears, and that the

cattle now kept half wild in certain parks, and those which have run quite

wild in two distant parts of the world, are likewise thus coloured. Now, an

experienced breeder, Mr. J. Beasley, of Northamptonshire (13/28. 'Gardener's

Chronicle and Agricultural Gazette' 1866 page 528.), crossed some carefully

selected West Highland cows with purely-bred shorthorn bulls. The bulls were

red, red and white, or dark roan; and the Highland cows were all of a red

colour, inclining to a light or yellow shade. But a considerable number of the

offspring--and Mr. Beasley calls attention to this as a remarkable fact--were

white, or white with red ears. Bearing in mind that none of the parents were

white, and that they were purely-bred animals, it is highly probable that here

the offspring reverted, in consequence of the cross, to the colour of some

ancient and half-wild parent-breed. The following case, perhaps, comes under

the same head: cows in their natural state have their udders but little

developed, and do not yield nearly so much milk as our domesticated animals.

Now there is some reason to believe (13/29. Ibid 1860 page 343. I am glad to

find that so experienced a breeder of cattle as Mr. Willoughby Wood,

'Gardener's Chronicle' 1869 page 1216, admits my principle of a cross giving a

tendency to reversion.) that cross-bred animals between two kinds, both of

which are good milkers, such as Alderneys and Shorthorns, often turn out

worthless in this respect.

In the chapter on the Horse reasons were assigned for believing that the

primitive stock was striped and dun-coloured; and details were given, showing

that in all parts of the world stripes of a dark colour frequently appear

along the spine, across the legs, and on the shoulders, where they are

occasionally double or treble, and even sometimes on the face and body of

horses of all breeds and of all colours. But the stripes appear most

frequently on the various kinds of duns. In foals they are sometimes plainly

seen, and subsequently disappear. The dun-colour and the stripes are strongly

transmitted when a horse thus characterised is crossed with any other; but I

was not able to prove that striped duns are generally produced from the

crossing of two distinct breeds, neither of which are duns, though this does

sometimes occur.

The legs of the ass are often striped, and this may be considered as a

reversion to the wild parent form, the Equus taeniopus of Abyssinia (13/30.

Sclater in 'Proc. Zoolog. Soc.' 1862 page 163.), which is generally thus

striped. In the domestic animal the stripes on the shoulder are occasionally

double, or forked at the extremity, as in certain zebrine species. There is

reason to believe that the foal is more frequently striped on the legs than

the adult animal. As with the horse, I have not acquired any distinct evidence

that the crossing of differently-coloured varieties of the ass brings out the

stripes.

But now let us turn to the result of crossing the horse and ass. Although

mules are not nearly so numerous in England as asses, I have seen a much

greater number with striped legs, and with the stripes far more conspicuous

than in either parent-form. Such mules are generally light-coloured, and might

be called fallow-duns. The shoulder-stripe in one instance was deeply forked

at the extremity, and in another instance was double, though united in the

middle. Mr. Martin gives a figure of a Spanish mule with strong zebra-like

marks on its legs (13/31. 'History of the Horse' page 212.), and remarks that

mules are particularly liable to be thus striped on their legs. In South

America, according to Roulin (13/32. 'Mem. presentes par divers Savans a

l'Acad. Royale' tome 6 1835 page 338.), such stripes are more frequent and

conspicuous in the mule than in the ass. In the United States, Mr. Gosse

(13/33. 'Letters from Alabama' 1859 page 280.), speaking of these animals,

says, "that in a great number, perhaps in nine out of every ten, the legs are

banded with transverse dark stripes."

Many years ago I saw in the Zoological Gardens a curious triple hybrid, from a

bay mare, by a hybrid from a male ass and female zebra. This animal when old

had hardly any stripes; but I was assured by the superintendent, that when

young it had shoulder-stripes, and faint stripes on its flanks and legs. I

mention this case more especially as an instance of the stripes being much

plainer during youth than in old age.

As the zebra has such a conspicuously striped body and legs, it might have

been expected that the hybrids from this animal and the common ass would have

had their legs in some degree striped; but it appears from the figures given

in Dr. Gray's 'Knowsley Gleanings' and still more plainly from that given by

Geoffroy and F. Cuvier (13/34. 'Hist. Nat. des Mammiferes' 1820 tome 1), that

the legs are much more conspicuously striped than the rest of the body; and

this fact is intelligible only on the belief that the ass aids in giving,

through the power of reversion, this character to its hybrid offspring.

The quagga is banded over the whole front part of its body like a zebra, but

has no stripes on its legs, or mere traces of them. But in the famous hybrid

bred by Lord Morton (13/35. 'Philosoph. Transact.' 1821 page 20.) from a

chestnut, nearly purely-bred, Arabian mare, by a male quagga, the stripes were

"more strongly defined and darker than those on the legs of "the quagga." The

mare was subsequently put to a black Arabian horse, and bore two colts, both

of which, as formerly stated, were plainly striped on the legs, and one of

them likewise had stripes on the neck and body.

The Equus indicus (13/36. Sclater in 'Proc. Zoolog. Soc.' 1862 page 163: this

species is the Ghor-Khur of N.W. India, and has often been called the Hemionus

of Pallas. See also Mr. Blyth's excellent paper in 'Journal of Asiatic Soc. of

Bengal' volume 28 1860 page 229.) is characterised by a spinal stripe, without

shoulder or leg stripes; but traces of these latter stripes may occasionally

be seen even in the adult (13/37. Another species of wild ass, the true E.

hemionus or Kiang, which ordinarily has no shoulder-stripes, is said

occasionally to have them; and these, as with the horse and ass, are sometimes

double: see Mr. Blyth in the paper just quoted and in 'Indian Sporting Review'

1856 page 320: and Col. Hamilton Smith in 'Nat. Library, Horses' page 318; and

'Dict. Class. d'Hist. Nat.' tome 3 page 563.) and Colonel S. Poole, who has

had ample opportunities for observation, informs me that in the foal, when

first born, the head and legs are often striped, but the shoulder-stripe is

not so distinct as in the domestic ass; all these stripes, excepting that

along the spine, soon disappear. Now a hybrid, raised at Knowsley (13/38.

Figured in the 'Gleanings from the Knowsley Menageries' by Dr. J.E. Gray.)

from a female of this species by a male domestic ass, had all four legs

transversely and conspicuously striped, had three short stripes on each

shoulder and had even some zebra-like stripes on its face! Dr. Gray informs me

that he has seen a second hybrid of the same parentage, similarly striped.

From these facts we see that the crossing of the several equine species tends

in a marked manner to cause stripes to appear on various parts of the body,

especially on the legs. As we do not know whether the parent-form of the genus

was striped, the appearance of the stripes can only hypothetically be

attributed to reversion. But most persons, after considering the many

undoubted cases of variously coloured marks reappearing by reversion in my

experiments on crossed pigeons and fowls, will come to the same conclusion

with respect to the horse-genus; and if so, we must admit that the progenitor

of the group was striped on the legs, shoulders, face, and probably over the

whole body, like a zebra.

Lastly, Professor Jaeger has given (13/39. 'Darwin'sche Theorie und ihre

Stellung zu Moral und Religion' page 85.) a good case with pigs. He crossed

the Japanese or masked breed with the common German breed, and the offspring

were intermediate in character. He then re-crossed one of these mongrels with

the pure Japanese, and in the litter thus produced one of the young resembled

in all its characters a wild pig; it had a long snout and upright ears, and

was striped on the back. It should be borne in mind that the young of the

Japanese breed are not striped, and that they have a short muzzle and ears

remarkably dependent.]

A similar tendency to the recovery of long lost characters holds good even

with the instincts of crossed animals. There are some breeds of fowls which

are called "everlasting layers," because they have lost the instinct of

incubation; and so rare is it for them to incubate that I have seen notices

published in works on poultry, when hens of such breeds have taken to sit.

(13/40. Cases of both Spanish and Polish hens sitting are given in the

'Poultry Chronicle' 1855 volume 3 page 477.) Yet the aboriginal species was of

course a good incubator; and with birds in a state of nature hardly any

instinct is so strong as this. Now, so many cases have been recorded of the

crossed offspring from two races, neither of which are incubators, becoming

first-rate sitters, that the reappearance of this instinct must be attributed

to reversion from crossing. One author goes so far as to say, "that a cross

between two non-sitting varieties almost invariably produces a mongrel that

becomes broody, and sits with remarkable steadiness." (13/41. 'The Poultry

Book' by Mr. Tegetmeier 1866 pages 119, 163. The author, who remarks on the

two negatives ('Journ. of Hort.' 1862 page 325), states that two broods were

raised from a Spanish cock and Silver-pencilled Hamburgh hen, neither of which

are incubators, and no less than seven out of eight hens in these two broods

"showed a perfect obstinacy in sitting." The Rev. E.S. Dixon ('Ornamental

Poultry' 1848 page 200) says that chickens reared from a cross between Golden

and Black Polish fowls, are "good and steady birds to sit." Mr. B.P. Brent

informs me that he raised some good sitting hens by crossing Pencilled

Hamburgh and Polish breeds. A cross-bred bird from a Spanish non-incubating

cock and Cochin incubating hen is mentioned in the 'Poultry Chronicle' volume

3 page 13, as an "exemplary mother." On the other hand, an exceptional case is

given in the 'Cottage Gardener' 1860 page 388 of a hen raised from a Spanish

cock and black Polish hen which did not incubate.) Another author, after

giving a striking example, remarks that the fact can be explained only on the

principle that "two negatives make a positive." It cannot, however, be

maintained that hens produced from a cross between two non-sitting breeds

invariably recover their lost instinct, any more than that crossed fowls or

pigeons invariably recover the red or blue plumage of their prototypes. Thus I

raised several chickens from a Polish hen by a Spanish cock,--breeds which do

not incubate,--and none of the young hens at first showed any tendency to sit;

but one of them--the only one which was preserved--in the third year sat well

on her eggs and reared a brood of chickens. So that here we have the

reappearance with advancing age of a primitive instinct, in the same manner as

we have seen that the red plumage of the Gallus bankiva is sometimes

reacquired both by crossed and purely-bred fowls of various kinds as they grow

old.

The parents of all our domesticated animals were of course aboriginally wild

in disposition; and when a domesticated species is crossed with a distinct

species, whether this is a domesticated or only a tamed animal, the hybrids

are often wild to such a degree, that the fact is intelligible only on the

principle that the cross has caused a partial return to a primitive

disposition. Thus, the Earl of Powis formerly imported some thoroughly

domesticated humped cattle from India, and crossed them with English breeds,

which belong to a distinct species; and his agent remarked to me, without any

question having been asked, how oddly wild the cross-bred animals were. The

European wild boar and the Chinese domesticated pig are almost certainly

specifically distinct: Sir F. Darwin crossed a sow of the latter breed with a

wild Alpine boar which had become extremely tame, but the young, though having

half-domesticated blood in their veins, were "extremely wild in confinement,

and would not eat swill like common English pigs." Captain Hutton, in India,

crossed a tame goat with a wild one from the Himalaya, and he remarked to me

how surprisingly wild the offspring were. Mr. Hewitt, who has had great

experience in crossing tame cock-pheasants with fowls belonging to five

breeds, gives as the character of all "extraordinary wildness" (13/42. 'The

Poultry Book' by Tegetmeier 1866 pages 165, 167.); but I have myself seen one

exception to this rule. Mr. S. J. Salter (13/43. 'Natural History Review' 1863

April page 277.) who raised a large number of hybrids from a bantam-hen by

Gallus sonneratii, states that "all were exceedingly wild." Mr. Waterton

(13/44. 'Essays on Natural History' page 917.) bred some wild ducks from eggs

hatched under a common duck, and the young were allowed to cross freely both

amongst themselves and with the tame ducks; they were "half wild and half

tame; they came to the windows to be fed, but still they had a wariness about

them quite remarkable."

On the other hand, mules from the horse and ass are certainly not in the least

wild, though notorious for obstinacy and vice. Mr. Brent, who has crossed

canary-birds with many kinds of finches, has not observed, as he informs me,

that the hybrids were in any way remarkably wild: but Mr. Jenner Weir who has

had still greater experience, is of a directly opposite opinion. He remarks

that the siskin is the tamest of finches, but its mules are as wild, when

young, as newly caught birds, and are often lost through their continued

efforts to escape. Hybrids are often raised between the common and musk duck,

and I have been assured by three persons, who have kept these crossed birds,

that they were not wild; but Mr. Garnett (13/45. As stated by Mr. Orton in his

'Physiology of Breeding' page 12.) observed that his hybrids were wild, and

exhibited "migratory propensities" of which there is not a vestige in the

common or musk duck. No case is known of this latter bird having escaped and

become wild in Europe or Asia, except, according to Pallas, on the Caspian

Sea; and the common domestic duck only occasionally becomes wild in districts

where large lakes and fens abound. Nevertheless, a large number of cases have

been recorded (13/46. M. E. de Selys-Longchamps refers ('Bulletin Acad. Roy.

de Bruxelles' tome 12 No. 10) to more than seven of these hybrids shot in

Switzerland and France. M. Deby asserts ('Zoologist' volume 5 1845-46 page

1254) that several have been shot in various parts of Belgium and Northern

France. Audubon ('Ornitholog. Biography' volume 3 page 168), speaking of these

hybrids, says that, in North America, they "now and then wander off and become

quite wild.") of hybrids from these two ducks having been shot in a completely

wild state, although so few are reared in comparison with purely-bred birds of

either species. It is improbable that any of these hybrids could have acquired

their wildness from the musk-duck having paired with a truly wild duck; and

this is known not to be the case in North America; hence we must infer that

they have reacquired, through reversion, their wildness, as well as renewed

powers of flight.

These latter facts remind us of the statements, so frequently made by

travellers in all parts of the world, on the degraded state and savage

disposition of crossed races of man. That many excellent and kind-hearted

mulattos have existed no one will dispute; and a more mild and gentle set of

men could hardly be found than the inhabitants of the island of Chiloe, who

consist of Indians commingled with Spaniards in various proportions. On the

other hand, many years ago, long before I had thought of the present subject,

I was struck with the fact that, in South America, men of complicated descent

between Negroes, Indians, and Spaniards, seldom had, whatever the cause might

be, a good expression. (13/47. 'Journal of Researches' 1845 page 71.)

Livingstone--and a more unimpeachable authority cannot be quoted,--after

speaking of a half-caste man on the Zambesi, described by the Portuguese as a

rare monster of inhumanity, remarks, "It is unaccountable why half-castes,

such as he, are so much more cruel than the Portuguese, but such is

undoubtedly the case." An inhabitant remarked to Livingstone, "God made white

men, and God made black men, but the Devil made halfcastes." (13/48.

'Expedition to the Zambesi' 1865 pages 25, 150.) When two races, both low in

the scale, are crossed the progeny seems to be eminently bad. Thus the noble-

hearted Humboldt, who felt no prejudice against the inferior races, speaks in

strong terms of the bad and savage disposition of Zambos, or half-castes

between Indians and Negroes; and this conclusion has been arrived at by

various observers. (13/49. Dr. P. Broca on 'Hybridity in the Genus Homo'

English translation 1864 page 39.) From these facts we may perhaps infer that

the degraded state of so many half-castes is in part due to reversion to a

primitive and savage condition, induced by the act of crossing, even if mainly

due to the unfavourable moral conditions under which they are generally

reared.

SUMMARY ON THE PROXIMATE CAUSES LEADING TO REVERSION.

When purely-bred animals or plants reassume long-lost characters,--when the

common ass, for instance, is born with striped legs, when a pure race of black

or white pigeons throws a slaty-blue bird, or when a cultivated heartsease

with large and rounded flowers produces a seedling with small and elongated

flowers,--we are quite unable to assign any proximate cause. When animals run

wild, the tendency to reversion, which, though it has been greatly

exaggerated, no doubt exists, is sometimes to a certain extent intelligible.

Thus, with feral pigs, exposure to the weather will probably favour the growth

of the bristles, as is known to be the case with the hair of other

domesticated animals, and through correlation the tusks will tend to be

redeveloped. But the reappearance of coloured longitudinal stripes on young

feral pigs cannot be attributed to the direct action of external conditions.

In this case, and in many others, we can only say that any change in the

habits of life apparently favour a tendency, inherent or latent in the

species, to return to the primitive state.

It will be shown in a future chapter that the position of flowers on the

summit of the axis, and the position of seeds within the capsule, sometimes

determine a tendency towards reversion; and this apparently depends on the

amount of sap or nutriment which the flower-buds and seeds receive. The

position, also, of buds, either on branches or on roots, sometimes determines,

as was formerly shown, the transmission of the character proper to the

variety, or its reversion to a former state.

We have seen in the last section that when two races or species are crossed

there is the strongest tendency to the reappearance in the offspring of long-

lost characters, possessed by neither parent nor immediate progenitor. When

two white, or red, or black pigeons, of well-established breeds, are united,

the offspring are almost sure to inherit the same colours; but when

differently-coloured birds are crossed, the opposed forces of inheritance

apparently counteract each other, and the tendency which is inherent in both

parents to produce slaty-blue offspring becomes predominant. So it is in

several other cases. But when, for instance, the ass is crossed with E.

indicus or with the horse--animals which have not striped legs--and the

hybrids have conspicuous stripes on their legs and even on their faces, all

that can be said is, that an inherent tendency to reversion is evolved through

some disturbance in the organisation caused by the act of crossing.

Another form of reversion is far commoner, indeed is almost universal with the

offspring from a cross, namely, to the characters proper to either pure

parent-form. As a general rule, crossed offspring in the first generation are

nearly intermediate between their parents, but the grandchildren and

succeeding generations continually revert, in a greater or lesser degree, to

one or both of their progenitors. Several authors have maintained that hybrids

and mongrels include all the characters of both parents, not fused together,

but merely mingled in different proportions in different parts of the body;

or, as Naudin (13/50. 'Nouvelles Archives du Museum' tome 1 page 151.) has

expressed it, a hybrid is a living mosaic-work, in which the eye cannot

distinguish the discordant elements, so completely are they intermingled. We

can hardly doubt that, in a certain sense, this is true, as when we behold in

a hybrid the elements of both species segregating themselves into segments in

the same flower or fruit, by a process of self-attraction or self-affinity;

this segregation taking place either by seminal or bud-propagation. Naudin

further believes that the segregation of the two specific elements or essences

is eminently liable to occur in the male and female reproductive matter; and

he thus explains the almost universal tendency to reversion in successive

hybrid generations. For this would be the natural result of the union of

pollen and ovules, in both of which the elements of the same species had been

segregated by self-affinity. If, on the other hand, pollen which included the

elements of one species happened to unite with ovules including the elements

of the other species, the intermediate or hybrid state would still be

retained, and there would be no reversion. But it would, as I suspect, be more

correct to say that the elements of both parent-species exist in every hybrid

in a double state, namely, blended together and completely separate. How this

is possible, and what the term specific essence or element may be supposed to

express, I shall attempt to show in the chapter on the hypothesis of

pangenesis.

But Naudin's view, as propounded by him, is not applicable to the reappearance

of characters lost long ago by variation; and it is hardly applicable to races

or species which, after having been crossed at some former period with a

distinct form, and having since lost all traces of the cross, nevertheless

occasionally yield an individual which reverts (as in the case of the great-

great-grandchild of the pointer Sappho) to the crossing form. The most simple

case of reversion, namely, of a hybrid or mongrel to its grandparents, is

connected by an almost perfect series with the extreme case of a purely-bred

race recovering characters which had been lost during many ages; and we are

thus led to infer that all the cases must be related by some common bond.

Gartner believed that only highly sterile hybrid plants exhibit any tendency

to reversion to their parent-forms. This erroneous belief may perhaps be

accounted for by the nature of the genera crossed by him, for he admits that

the tendency differs in different genera. The statement is also directly

contradicted by Naudin's observations, and by the notorious fact that

perfectly fertile mongrels exhibit the tendency in a high degree,--even in a

higher degree, according to Gartner himself, than hybrids. (13/51.

'Bastarderzeugung' s. 582, 438, etc.)

Gartner further states that reversions rarely occur with hybrid plants raised

from species which have not been cultivated, whilst, with those which have

been long cultivated, they are of frequent occurrence. This conclusion

explains a curious discrepancy: Max Wichura (13/52. 'Die Bastardbefruchtung...

der Weiden' 1865 s. 23. For Gartner's remarks on this head, see

'Bastarderzeugung' s. 474, 582.) who worked exclusively on willows which had

not been subjected to culture, never saw an instance of reversion; and he goes

so far as to suspect that the careful Gartner had not sufficiently protected

his hybrids from the pollen of the parent-species: Naudin, on the other hand,

who chiefly experimented on cucurbitaceous and other cultivated plants,

insists more strenuously than any other author on the tendency to reversion in

all hybrids. The conclusion that the condition of the parent-species, as

affected by culture, is one of the proximate causes leading to reversion,

agrees well with the converse case of domesticated animals and cultivated

plants being liable to reversion when they become feral; for in both cases the

organisation or constitution must be disturbed, though in a very different

way. (13/53. Prof. Weismann in his very curious essay on the different forms

produced by the same species of butterfly at different seasons ('Saison-

Dimorphismus der Schmetterlinge' pages 27, 28), has come to a similar

conclusion, namely, that any cause which disturbs the organisation, such as

the exposure of the cocoons to heat or even to much shaking, gives a tendency

to reversion.)

Finally, we have seen that characters often reappear in purely-bred races

without our being able to assign any proximate cause; but when they become

feral this is either indirectly or directly induced by the change in their

conditions of life. With crossed breeds, the act of crossing in itself

certainly leads to the recovery of long-lost characters, as well as of those

derived from either parent-form. Changed conditions, consequent on

cultivation, and the relative position of buds, flowers, and seeds on the

plant, all apparently aid in giving this same tendency. Reversion may occur

either through seminal or bud generation, generally at birth, but sometimes

only with an advance of age. Segments or portions of the individual may alone

be thus affected. That a being should be born resembling in certain characters

an ancestor removed by two or three, and in some cases by hundreds or even

thousands of generations, is assuredly a wonderful fact. In these cases the

child is commonly said to inherit such characters directly from its

grandparent, or more remote ancestors. But this view is hardly conceivable.

If, however, we suppose that every character is derived exclusively from the

father or mother, but that many characters lie latent or dormant in both

parents during a long succession of generations, the foregoing facts are

intelligible. In what manner characters may be conceived to lie latent, will

be considered in a future chapter to which I have lately alluded.

LATENT CHARACTERS.

But I must explain what is meant by characters lying latent. The most obvious

illustration is afforded by secondary sexual characters. In every female all

the secondary male characters, and in every male all the secondary female

characters, apparently exist in a latent state, ready to be evolved under

certain conditions. It is well known that a large number of female birds, such

as fowls, various pheasants, partridges, peahens, ducks, etc., when old or

diseased, or when operated on, assume many or all of the secondary male

characters of their species. In the case of the hen-pheasant this has been

observed to occur far more frequently during certain years than during others.

(13/54. Yarrell 'Phil. Transact.' 1827 page 268; Dr. Hamilton in 'Proc.

Zoolog. Soc.' 1862 page 23.) A duck ten years old has been known to assume

both the perfect winter and summer plumage of the drake. (13/55. 'Archiv.

Skand. Beitrage zur Naturgesch.' 8 s. 397-413.) Waterton (13/56. In his

'Essays on Nat. Hist.' 1838 Mr. Hewitt gives analogous cases with hen-

pheasants in 'Journal of Horticulture' July 12, 1864 page 37. Isidore Geoffroy

Saint-Hilaire in his 'Essais de Zoolog. Gen.' ('Suites a Buffon' 1842 pages

496-513), has collected such cases in ten different kinds of birds. It appears

that Aristotle was well aware of the change in mental disposition in old hens.

The case of the female deer acquiring horns is given at page 513.) gives a

curious case of a hen which had ceased laying, and had assumed the plumage,

voice, spurs, and warlike disposition of the cock; when opposed to an enemy

she would erect her hackles and show fight. Thus every character, even to the

instinct and manner of fighting, must have lain dormant in this hen as long as

her ovaria continued to act. The females of two kinds of deer, when old, have

been known to acquire horns; and, as Hunter has remarked, we see something of

an analogous nature in the human species.

On the other hand, with male animals, it is notorious that the secondary

sexual characters are more or less completely lost when they are subjected to

castration. Thus, if the operation be performed on a young cock, he never, as

Yarrell states, crows again; the comb, wattles, and spurs do not grow to their

full size, and the hackles assume an intermediate appearance between true

hackles and the feathers of the hen. Cases are recorded of confinement, which

often affects the reproductive system, causing analogous results. But

characters properly confined to the female are likewise acquired by the male;

the capon takes to sitting on eggs, and will bring up chickens; and what is

more curious, the utterly sterile male hybrids from the pheasant and the fowl

act in the same manner, "their delight being to watch when the hens leave

their nests, and to take on themselves the office of a sitter." (13/57.

'Cottage Gardener' 1860 page 379.) That admirable observer Reaumur (13/58.

'Art de faire Eclore' etc. 1749 tome 2 page 8.) asserts that a cock, by being

long confined in solitude and darkness, can be taught to take charge of young

chickens; he then utters a peculiar cry, and retains during his whole life

this newly acquired maternal instinct. The many well-ascertained cases of

various male mammals giving milk shows that their rudimentary mammary glands

retain this capacity in a latent condition.

We thus see that in many, probably in all cases, the secondary characters of

each sex lie dormant or latent in the opposite sex, ready to be evolved under

peculiar circumstances. We can thus understand how, for instance, it is

possible for a good milking cow to transmit her good qualities through her

male offspring to future generations; for we may confidently believe that

these qualities are present, though latent, in the males of each generation.

So it is with the game-cock, who can transmit his superiority in courage and

vigour through his female to his male offspring; and with man it is known

(13/59. Sir H. Holland 'Medical Notes and Reflections' 3rd edition 1855 page

31.) that diseases, such as hydrocele, necessarily confined to the male sex,

can be transmitted through the female to the grandson. Such cases as these

offer, as was remarked at the commencement of this chapter, the simplest

possible examples of reversion; and they are intelligible on the belief that

characters common to the grandparent and grandchild of the same sex are

present, though latent, in the intermediate parent of the opposite sex.

The subject of latent characters is so important, as we shall see in a future

chapter, that I will give another illustration. Many animals have the right

and left sides of their body unequally developed: this is well known to be the

case with flat-fish, in which the one side differs in thickness and colour and

in the shape of the fins, from the other, and during the growth of the young

fish one eye is gradually twisted from the lower to the upper surface. (13/60.

See Steenstrup on the 'Obliquity of Flounders' in Annals and Mag. of Nat.

Hist.' May 1865 page 361. I have given an abstract of Malm's explanation of

this wonderful phenomenon in the 'Origin of Species' 6th Edition page 186.) In

most flat-fishes the left is the blind side, but in some it is the right;

though in both cases reversed or "wrong fishes," are occasionally developed;

and in Platessa flesus the right or left side is indifferently the upper one.

With gasteropods or shell-fish, the right and left sides are extremely unlike;

the far greater number of species are dextral, with rare and occasional

reversals of development; and some few are normally sinistral; but certain

species of Bulimus, and many Achatinellae (13/61. Dr. E. von Martens in

'Annals and Mag. of Nat. Hist.' March 1866 page 209.) are as often sinistral

as dextral. I will give an analogous case in the great articulate kingdom: the

two sides of Verruca (13/62. Darwin 'Balanidae' Ray Soc. 1854 page 499: see

also the appended remarks on the apparently capricious development of the

thoracic limbs on the right and left sides in the higher crustaceans.) are so

wonderfully unlike, that without careful dissection it is extremely difficult

to recognise the corresponding parts on the opposite sides of the body; yet it

is apparently a mere matter of chance whether it be the right or the left side

that undergoes so singular amount of change. One plant is known to me (13/63.

Mormodes ignea: Darwin 'Fertilisation of Orchids' 1862 page 251.) in which the

flower, according as it stands on the one or other side of the spike, is

unequally developed. In all the foregoing cases the two sides are perfectly

symmetrical at an early period of growth. Now, whenever a species is as liable

to be unequally developed on the one as on the other side, we may infer that

the capacity for such development is present, though latent, in the

undeveloped side. And as a reversal of development occasionally occurs in

animals of many kinds, this latent capacity is probably very common.

The best yet simplest cases of characters lying dormant are, perhaps, those

previously given, in which chickens and young pigeons, raised from a cross

between differently coloured birds, are at first of one colour, but in a year

or two acquire feathers of the colour of the other parent; for in this case

the tendency to a change of plumage is clearly latent in the young bird. So it

is with hornless breeds of cattle, some of which acquire small horns as they

grow old. Purely bred black and white bantams, and some other fowls,

occasionally assume, with advancing years, the red feathers of the parent-

species. I will here add a somewhat different case, as it connects in a

striking manner latent characters of two classes. Mr. Hewitt (13/64. 'Journal

of Horticulture' July 1864 page 38. I have had the opportunity of examining

these remarkable feathers through the kindness of Mr. Tegetmeier.) possessed

an excellent Sebright gold-laced bantam hen, which, as she became old, grew

diseased in her ovaria, and assumed male characters. In this breed the males

resemble the females in all respects except in their combs, wattles, spurs,

and instincts; hence it might have been expected that the diseased hen would

have assumed only those masculine characters which are proper to the breed,

but she acquired, in addition, well-arched tail sickle-feathers quite a foot

in length, saddle-feathers on the loins, and hackles on the neck,--ornaments

which, as Mr. Hewitt remarks, "would be held as abominable in this breed." The

Sebright bantam is known (13/65. 'The Poultry Book' by Mr. Tegetmeier 1866

page 241.) to have originated about the year 1800 from a cross between a

common bantam and a Polish fowl, recrossed by a hen-tailed bantam, and

carefully selected; hence there can hardly be a doubt that the sickle-feathers

and hackles which appeared in the old hen were derived from the Polish fowl or

common bantam; and we thus see that not only certain masculine characters

proper to the Sebright bantam, but other masculine characters derived from the

first progenitors of the breed, removed by a period of above sixty years, were

lying latent in this henbird, ready to be evolved as soon as her ovaria became

diseased.

From these several facts it must be admitted that certain characters,

capacities, and instincts, may lie latent in an individual, and even in a

succession of individuals, without our being able to detect the least sign of

their presence. When fowls, pigeons, or cattle of different colours are

crossed, and their offspring change colour as they grow old, or when the

crossed turbit acquired the characteristic frill after its third moult, or

when rarely-bred bantams partially assume the red plumage of their prototype,

we cannot doubt that these qualities were from the first present, though

latent, in the individual animal, like the characters of a moth in the

caterpillar. Now, if these animals had produced offspring before they had

acquired with advancing age their new characters, nothing is more probable

than that they would have transmitted them to some of their offspring, who in

this case would in appearance have received such characters from their grand-

parents or more distant progenitors. We should then have had a case of

reversion, that is, of the reappearance in the child of an ancestral

character, actually present, though during youth completely latent, in the

parent; and this we may safely conclude is what occurs in all reversions to

progenitors, however remote.

This view of the latency in each generation of all the characters which appear

through reversion, is also supported by their actual presence in some cases

during early youth alone, or by their more frequent appearance and greater

distinctness at this age than during maturity. We have seen that this is often

the case with the stripes on the legs and faces of the several species of the

horse genus. The Himalayan rabbit, when crossed, sometimes produces offspring

which revert to the parent silver-grey breed, and we have seen that in purely

bred animals pale-grey fur occasionally reappears during early youth. Black

cats, we may feel assured, would occasionally produce by reversion tabbies;

and on young black kittens, with a pedigree (13/66. Carl Vogt 'Lectures on

Man' English translation 1864 page 411.) known to have been long pure, faint

traces of stripes may almost always be seen which afterwards disappear.

Hornless Suffolk cattle occasionally produce by reversion horned animals; and

Youatt (13/67. 'On Cattle' page 174.) asserts that even in hornless

individuals "the rudiment of a horn may be often felt at an early age."

No doubt it appears at first sight in the highest degree improbable that in

every horse of every generation there should be a latent capacity and tendency

to produce stripes, though these may not appear once in a thousand

generations; that in every white, black, or other coloured pigeon, which may

have transmitted its proper colour during centuries, there should be a latent

capacity in the plumage to become blue and to be marked with certain

characteristic bars; that in every child in a six-fingered family there should

be the capacity for the production of an additional digit; and so in other

cases. Nevertheless, there is no more inherent improbability in this being the

case than in a useless and rudimentary organ, or even in only a tendency to

the production of a rudimentary organ, being inherited during millions of

generations, as is well known to occur with a multitude of organic beings.

There is no more inherent improbability in each domestic pig, during a

thousand generations, retaining the capacity and tendency to develop great

tusks under fitting conditions, than in the young calf having retained, for an

indefinite number of generations rudimentary incisor teeth, which never

protrude through the gums.

I shall give at the end of the next chapter a summary of the three preceding

chapters; but as isolated and striking cases of reversion have here been

chiefly insisted on, I wish to guard the reader against supposing that

reversion is due to some rare or accidental combination of circumstances. When

a character, lost during hundreds of generations, suddenly reappears, no doubt

some such combination must occur; but reversions, to the immediately preceding

generations may be constantly observed, at least, in the offspring of most

unions. This has been universally recognised in the case of hybrids and

mongrels, but it has been recognised simply from the difference between the

united forms rendering the resemblance of the offspring to their grandparents

or more remote progenitors of easy detection. Reversion is likewise almost

invariably the rule, as Mr. Sedgwick has shown, with certain diseases. Hence

we must conclude that a tendency to this peculiar form of transmission is an

integral part of the general law of inheritance.

MONSTROSITIES.

A large number of monstrous growths and of lesser anomalies are admitted by

every one to be due to an arrest of development, that is, to the persistence

of an embryonic condition. But many monstrosities cannot be thus explained;

for parts of which no trace can be detected in the embryo, but which occur in

other members of the same class of animals occasionally appear, and these may

probably with truth be attributed to reversion. As, however, I have treated

this subject as fully as I could in my 'Descent of Man' (ch. 1 2nd edition), I

will not here recur to it.

[When flowers which have normally an irregular structure become regular or

peloric, the change is generally looked at by botanists as a return to the

primitive state. But Dr. Maxwell Masters (13/68. 'Natural Hist. Review' April

1863 page 258. See also his Lecture, Royal Institution, March 16, 1860. On

same subject see Moquin-Tandon 'Elements de Teratologie' 1841 pages 184, 352.

Dr. Peyritsch has collected a large number of very interesting cases 'Sitzb.

d. k. Akad. d. Wissensch.' Wien b. 60 and especially b. 66 1872 page 125.),

who has ably discussed this subject, remarks that when, for instance, all the

sepals of a Tropaeolum become green and of the same shape, instead of being

coloured with one prolonged into a spur, or when all the petals of a Linaria

become simple and regular, such cases may be due merely to an arrest of

development; for in these flowers all the organs during their earliest

condition are symmetrical, and, if arrested at this stage of growth, they

would not become irregular. If, moreover, the arrest were to take place at a

still earlier period of development, the result would be a simple tuft of

green leaves; and no one probably would call this a case of reversion. Dr.

Masters designates the cases first alluded to as regular peloria; and others,

in which all the corresponding parts assume a similar form of irregularity, as

when all the petals in a Linaria become spurred, as irregular peloria. We have

no right to attribute these latter cases to reversion, until it can be shown

that the parent-form, for instance, of the genus Linaria had had all its

petals spurred; for a chance of this nature might result from the spreading of

an anomalous structure, in accordance with the law, to be discussed in a

future chapter, of homologous parts tending to vary in the same manner. But as

both forms of peloria frequently occur on the same individual plant of the

Linaria (13/69. Verlot 'Des Varietes' 1865 page 89; Naudin 'Nouvelles Archives

du Museum' tome 1 page 137.), they probably stand in some close relation to

one another. On the doctrine that peloria is simply the result of an arrest of

development, it is difficult to understand how an organ arrested at a very

early period of growth should acquire its full functional perfection;--how a

petal, supposed to be thus arrested, should acquire its brilliant colours, and

serve as an envelope to the flower, or a stamen produce efficient pollen; yet

this occurs with many peloric flowers. That pelorism is not due to mere chance

variability, but either to an arrest of development or to reversion, we may

infer from an observation made by Ch. Morren (13/70. In his discussion on some

curious peloric Calceolarias quoted in 'Journal of Horticulture' February 24,

1863 page 152.) namely, that families which have irregular flowers often

"return by these monstrous growths to their regular form; whilst we never see

a regular flower realise the structure of an irregular one."

Some flowers have almost certainly become more or less completely peloric

through reversion, as the following interesting case shows. Corydalis tuberosa

properly has one of its two nectaries colourless, destitute of nectar, only

half the size of the other, and therefore, to a certain extent, in a

rudimentary state; the pistil is curved towards the perfect nectary, and the

hood, formed of the inner petals, slips off the pistil and stamen in one

direction alone, so that, when a bee sucks the perfect nectary, the stigma and

stamens are exposed and rubbed against the insect's body. In several closely

allied genera, as in Dielytra, etc., there are two perfect nectaries, the

pistil is straight, and the hood slips off on either side, according as the

bee sucks either nectary. Now, I have examined several flowers of Corydalis

tuberosa, in which both nectaries were equally developed and contained nectar;

in this we see only the redevelopment of a partially aborted organ; but with

this redevelopment the pistil becomes straight, and the hood slips off in

either direction, so that these flowers have acquired the perfect structure,

so well adapted for insect agency, of Dielytra and its allies. We cannot

attribute these coadapted modifications to chance, or to correlated

variability; we must attribute them to reversion to a primordial condition of

the species.

The peloric flowers of Pelargonium have their five petals in all respects

alike, and there is no nectary so that they resemble the symmetrical flowers

of the closely allied genus Geranium; but the alternate stamens are also

sometimes destitute of anthers, the shortened filaments being left as

rudiments, and in this respect they resemble the symmetrical flowers of the

closely allied genus Erodium. Hence we may look at the peloric flowers of

Pelargonium as having reverted to the state of some primordial form, the

progenitor of the three closely related genera of Pelargonium, Geranium, and

Erodium.

In the peloric form of Antirrhinum majus, appropriately called the" Wonder,"

the tubular and elongated flowers differ wonderfully from those of the common

snapdragon; the calyx and the mouth of the corolla consist of six equal lobes,

and include six equal instead of four unequal stamens. One of the two

additional stamens is manifestly formed by the development of a

microscopically minute papilla, which may be found at the base of the upper

lip of the flower of the common snapdragons in the nineteen plants examined by

me. That this papilla is a rudiment of a stamen was well shown by its various

degrees of development in crossed plants between the common and the peloric

Antirrhinum. Again, a peloric Galeobdolon luteum, growing in my garden, had

five equal petals, all striped like the ordinary lower lip, and included five

equal instead of four unequal stamens; but Mr. R. Keeley, who sent me this

plant, informs me that the flowers vary greatly, having from four to six lobes

to the corolla, and from three to six stamens. (13/71. For other cases of six

divisions in peloric flowers of the Labiatae and Scrophulariaceae see Moquin-

Tandon 'Teratologie' page 192.) Now, as the members of the two great families

to which the Antirrhinum and Galeobdolon belong are properly pentamerous, with

some of the parts confluent and others suppressed, we ought not to look at the

sixth stamen and the sixth lobe to the corolla in either case as due to

reversion, any more than the additional petals in double flowers in these same

two families. But the case is different with the fifth stamen in the peloric

Antirrhinum, which is produced by the redevelopment of a rudiment always

present, and which probably reveals to us the state of the flower, as far as

the stamens are concerned, at some ancient epoch. It is also difficult to

believe that the other four stamens and the petals, after an arrest of

development at a very early embryonic age, would have come to full perfection

in colour, structure, and function, unless these organs had at some former

period normally passed through a similar course of growth. Hence it appears to

me probable that the progenitor of the genus Antirrhinum must at some remote

epoch have included five stamens and borne flowers in some degree resembling

those now produced by the peloric form. The conclusion that peloria is not a

mere monstrosity, irrespective of any former state of the species, is

supported by the fact that this structure is often strongly inherited, as in

the case of the peloric Antirrhinum and Gloxinia and sometimes in that of the

peloric Corydalis solida. (13/72. Godron reprinted from the 'Memoires de

l'Acad. de Stanislas' 1868.)

Lastly I may add that many instances have been recorded of flowers, not

generally considered as peloric, in which certain organs are abnormally

augmented in number. As an increase of parts cannot be looked at as an arrest

of development, nor as due to the redevelopment of rudiments, for no rudiments

are present, and as these additional parts bring the plant into closer

relationship with its natural allies, they ought probably to be viewed as

reversions to a primordial condition.]

These several facts show us in an interesting manner how intimately certain

abnormal states are connected together; namely, arrests of development causing

parts to become rudimentary or to be wholly suppressed,--the redevelopment of

parts now in a more or less rudimentary condition,--the reappearance of organs

of which not a vestige can be detected,--and to these may be added, in the

case of animals, the presence during youth, and subsequent disappearance, of

certain characters which occasionally are retained throughout life. Some

naturalists look at all such abnormal structures as a return to the ideal

state of the group to which the affected being belongs; but it is difficult to

conceive what is meant to be conveyed by this expression. Other naturalists

maintain, with greater probability and distinctness of view, that the common

bond of connection between the several foregoing cases is an actual, though

partial, return to the structure of the ancient progenitor of the group. If

this view be correct, we must believe that a vast number of characters,

capable of evolution, lie hidden in every organic being. But it would be a

mistake to suppose that the number is equally great in all beings. We know,

for instance, that plants of many orders occasionally become peloric; but many

more cases have been observed in the Labiatae and Scrophulariaceae than in any

other order; and in one genus of the Scrophulariaceae, namely Linaria, no less

than thirteen species have been described in this condition (13/73. Moquin-

Tandon 'Teratologie' page 186.) On this view of the nature of peloric flowers,

and bearing in mind certain monstrosities in the animal kingdom, we must

conclude that the progenitors of most plants and animals have left an

impression, capable of redevelopment, on the germs of their descendants,

although these have since been profoundly modified.

The fertilised germ of one of the higher animals, subjected as it is to so

vast a series of changes from the germinal cell to old age,--incessantly

agitated by what Quatrefages well calls the tourbillon vital,--is perhaps the

most wonderful object in nature. It is probable that hardly a change of any

kind affects either parent, without some mark being left on the germ. But on

the doctrine of reversion, as given in this chapter, the germ becomes a far

more marvellous object, for, besides the visible changes which it undergoes,

we must believe that it is crowded with invisible characters, proper to both

sexes, to both the right and left side of the body, and to a long line of male

and female ancestors separated by hundreds or even thousands of generations

from the present time: and these characters, like those written on paper with

invisible ink, lie ready to be evolved whenever the organisation is disturbed

by certain known or unknown conditions.