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ALBINO
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ALBINO , a biological See also:term (See also:Lat. albus, See also: In these animals the eyeball and the See also:fur of the See also:body are unpigmented, but the tips of the See also:ear pinnae and extremities of the fore and See also:hind limbs, together with the tail, are marked by more or less well defined colour. One remarkable feature of these animals is that for a few months after See also:birth they are complete albinoes. Occasion-ally, however, some are See also:born with a See also:grey colour and a few may be quite black, but ultimately they attain their characteristic coat. There is some reason to believe, as we shall see later, that in spite of the presence of a little pigment and of occasional wholly pigmented See also:young ones, ' Himalayans must be regarded as true albinoes. Other individual rabbits, but belonging to no particular breed, are similarly marked, but in addition tilt eyeballs are black. Some domesticated mice are entirely white with the exception that they have black eyeballs; and individuals of this type are known in which there is a reduction of pigment in the eyeballs, and since the colour of the blood is then partially visible these appear of a reddish-black colour. Such cases are interesting as representing the last step in the graded See also:series through which the condition of complete pigmentation passes into that of complete albinism. There is See also:evidence, as shown by G. M. See also:Allen, that partial albinism is a condition in which pigment is reduced around definite body centres, so that unpigmented areas occur between the pigment patches or at their See also:borders. In the See also:mouse, ten such centres may be distinguished, arranged symmetrically five on either See also:side of the median plane—a cheek patch, See also:neck patch, See also:shoulder patch, side patch and rump patch. Various degrees in the reduction of the pigment patches up to that of complete elimination may be traced. Some animals are wholly pigmented during the summer and autumn, but through the See also:winter and See also:spring they are in the condition of extreme partial albinism and become almost complete albinoes. Such instances are found in the Scotch See also:blue hare (Lefts timidus), in the See also:Norway hare, in the See also:North See also:American hare (L. americanus), in the See also:arctic See also:fox (Canis lagopus), in the stoat and See also:ermine, and among birds, in the See also:ptarmigan, and some other See also:species of Lagopus. How the See also:change from the autumnal to the winter condition takes See also:place appears not to be definitely settled in all cases, and accurate observations are much to be desired. In the See also:case of the Norway hare, it has been stated that a general See also:moult, including all the hairs and under fur, takes place and new white hairs are substituted. The See also:process of moulting is said to begin in the See also:middle of autumn and is completed before the end of See also:December, by which See also:time the fur is in its winter condition, and is closer, See also:fuller and longer than in summer (Naturalists' Library, vol. vii.). On the other See also:hand, it has been stated that during the whole of the transformation in the fur no hairs fall from the See also:animal, and it is attributed to an actual change in the colour of the See also:hair (See also:Edinburgh Philosophical See also:Journal, vol. xi. p. 1o1). In the case of the American hare, however, some very careful observations have been made by F. H. Welch. In this animal the See also:long hairs (which See also:form the See also:pile) become white at their extremities, and in some of them this whiteness extends through their whole length. At the same time, new hairs begin to develop and to grow rapidly, and soon outstrip 'the hairs of the autumn pile. From their first See also:appearance these new hairs are white and stiff, and they are confined to the sides and back of the body. It is not clear from Welch's See also:account what is the cause of the whiteness of the tips of the hairs of the autumn coat, but his figures suggest that it is due to the development of See also:gas in the interspaces between the keratin See also:bridges and trabeculae of the hairs. There is nothing to show whether the pigment persists or is absorbed. Probably it persists. In this event, the whiteness of the tips will be due to the scattering or irregular reflexion of the incident rays of light from the See also:surface of the numerous gas bubbles. In the case of the ptarmigan the evidence is clear that the existing autumnal feathers do change, more or less completely, to white. But the evidence is not conclusive as to whether any See also:part of the winter condition is additionally produced by moulting. The condition of albinism thus assumed as a seasonal variation is never complete, for the eyes at least retain their pigmented See also:state. The reason of this is readily understood when it is See also:borne in mind how disadvantageous to the See also:function of sight is the unpigmented condition of an albino's eyeball; a disadvantage which would be probably much accentuated, in the cases now under See also:consideration, by the See also:bright glare from the surface of the See also:snow, which forms the natural environment of these animals at the particular See also:period of the See also:year when the winter change occurs. In some cases, as in all the varying See also:hares, in addition to the eyes retaining their normal pigmentation, areas similar in extent and situation to those on the Himalayan rabbits also retain their pigmentation; and in the ptarmigan there is a black See also:band on each side of the See also:head stretching forwards and backwards from the eyeball, and the See also:outer tail feathers are black. Albinism is restricted to no particular class of the animal See also:kingdom; for partial albinism at least is known to occur in See also:Coelentera, See also:worms, See also:Crustacea, See also:Myriapoda, See also:Coleoptera,See also:Arachnida and fishes. The individuals in which this diminished pigmentation is found are for the most part those living in caves, and it is probable that their condition is not truly albinotic, but only temporary and due to the absence of the stimulus of light. This may be also true of some of those instances that have occurred among frogs, in See also:Proteus, and with an axolotl507
once possessed by the present writer. This latter animal was quite white, with the exception of the black eyeballs. At the end of four See also:weeks after it was first See also:purchased the dorsal cr upper surface of its See also:external gills See also:developed a small amount of dark pigment. Within the next few weeks this increased in quantity and the dorsal surface of the head and of the front end of the See also:trunk began to be pigmented. The animal died at the end of the eighth See also:week, but it is possible that had it lived it would have become wholly pigmented. But, apart from these instances, albinism is known, according to W. E. See also:Castle, who cites it on the authority of See also:Hugh M. See also: Instances of the latter condition are very See also:common among the negroes of the See also:United States and of See also:South America, and in them assumes a piebald character, irregular white patches being scattered over the general black surface of the body. Occasionally the piebald patches tend to be symmetrically arranged, and sometimes the eyeballs are pigmentless (pink) and sometimes pigmented (black). According to A. R. Gunn, of Edinburgh University, who has recently been investigating the subject of albinism in man, there is reason to believe that a condition of piebald albinism occurs also in Europeans (Scotsmen). He has examined subjects in. which the whole of the hair of the body is white, but the eyeballs are pigmented, often deeply; and, conversely, he has seen cases in which the eyes are pink but the hair is pigmented. The hair and the eyes may be regarded as skin patches, in which some-times the one and sometimes the other is pigmentless. He believes that, were it not for the generally very See also:pale colour of white-skinned races, this piebald condition would be as See also:manifest in them as in negroes, over the whole surface of the body. In complete human albinoes, albinism is correlated, in addition to nystagmus, with a peculiar roughness of the skin, making it harsh to the See also:touch. The skin is also milky-white in appearance. According to C. J. Seligmann, there exists among the See also:Papuans an albinotic race whose skin varies in colour from a pink-white to that of cafe au See also:Tait; the eyes are generally greenish, See also:hazel or See also: The colour of this substance is that of the pigment in the skin or hairs of the animal used. Miss Durham interprets her results as indicating that the skin of these pigmented animals normally secretes one or more tyrosinases. The same result was obtained from the skins of some unhatched chickens. The skins of albinoes gave no results. Not only have such results been obtained with sponges, Insects, cephalopods, birds and mammals, but Em. Bourquelot and G. See also:Bertrand have shown that certain See also:fungi, the tissues of which, when exposed to the See also:air by injury, become immediately coloured, do so owing to the See also:action of tyrosinase upon one or more chromogenous substances present in the plant. We may conceive, then, that a pigmented animal owes its colour to the power that certain tissues of its body possess to secrete both tyrosinases and chromogenic substances. And the period at which this process is most active is at birth, or preceding it or immediately succeeding it. In spite of the inquiry being only in its initial stages, there is already See also:good evidence to believe that Cuenot's theory is correct, and that an albino is an individual whose skin lacks the power to secrete either the ferment or the chromogen. It forms one but not both of these substances. A moment's consideration, however, will show that, while an albino may be an individual in which one or more of the complementary bodies of pigmentation are absent, a pigmented animal is something more than an individual which carries all the factors necessary for the development of colour. For it must be borne in mind that animals are not only coloured but the colour is arranged in a more or less definite See also:pattern. The wild mouse, See also:rat and See also:rabbit are self-coloured, but the domesticated forms include various piebald patterns, such as spotted forms among mice, and the See also:familiar black and white hooded and dorsal-striped pattern of some tame rats. Colour, therefore, must be correlated with some See also:determinant (determining See also:factor) for pattern, and it cannot, therefore, exist alone in an animal's coat. And we must conceive that each See also:kind of pattern—the self, the spotted, the striped, the hooded and all others—has its own See also:special, determinant. Given the presence of all the necessary determinnts for the development of pigment in a mammal's coat, some or all of the hairs may bear this pigment according to the pattern determinants, or absence of pattern determinants, which the cells of the hair papillae carry. And this brings us to the question as to whether in a piebald animal the pigmented hairs are in any way different from the pigmentless or white hairs. No adequate investigation of this subject has yet been made, but some observations made by the author of this See also:article, on the piebald black and white rat, show that See also:differences connected with the microscopic structure exist. There is thus evidence that colour is correlated with other factors which determine pattern. And this leads to the inquiry as to whether albinoes ever exhibit evidence that they carry the pattern determinants in the absence of those for pigmentation. For it is to be expected a priori that, since albinoes were derived from pigmented progenitors and may at any time appear, side by side with pigmented See also:brothers, in a See also:litter from pigmented parents, they would be carrying the pattern determinants of some one or other of their pigmented ancestors. Now we know, from the numerous experiments in See also:heredity which have resulted since the rediscovery of Mendel's principles, that an individual may carry a character in one of two conditions. It may be carried as a somatic character, when it will be visible in the body tissues, or it may be carried as a gametic character, and its presence can only then be detected in subsequent generations, by adequately devised breeding tests. With regard to pattern, the evidence is now dear that albinoes may carry the determinants in both these ways. So far as they are carried gametically, i.e. by the See also:sex-cells, it has been shown by Cuenot and G. M. Allen for mice, by C. C. See also:Hurst for rabbits, and by L. See also:Doncaster and G. P. Mudge for rats, that in a See also:cross between a coloured individual of known gametic purity and an albino, the individuals of the progeny in either the first or second, or both generations, may differ, and that the difference in somecases wholly depends upon the albino used. It has been shown that the individuals in such an offspring may bear patterns which never occurred in the ancestry of the coloured See also:parent, but did in that of the albino; and, moreover, if the same coloured parent be mated with another individual, either albino or coloured, that their offspring may never contain members bearing such patterns. The particular pattern will only appear when the coloured parent is mated with the particular albino. And yet the albino itself shows no somatic pattern or pigment. So dear is the evidence on this point that any one adequately acquainted at first hand with the phenomena, by employing an albino of known gametic structure and mating it with a coloured individual, also of known gametic constitution, could predict the result. With respect to albinoes carrying pattern as a visible somatic character, i.e. in the body cells, no definite evidence has as yet been published. But W. Haacke has described a single albino rat, in which he states that the hairs of the shoulder and See also:mid-dorsal, regions were of a different texture from those of the See also:rest of the body. And it is possible that this albino, had it developed colour, would have been of the piebald pattern. But the author of this article has quite recently reared some albinoes in which the familiar shoulder See also:hood and dorsal stripe of the piebald rat is perfectly obvious, in spite of the absence of the slightest pigmentation. The hairs which occupy the region which in the pigmented individual is black, are longer, thinner and more widely separated than those in the regions which are white. As a result of this, the pink skin is quite visible where these hairs occur, but elsewhere it is invisible. Thus these albinoes exhibit a pattern of pink skin similar in form with the black pattern of the piebald rat. Moreover, some of the albinoes possess these particular " pattern " hairs all over the body and obviously such individuals are carrying the self pattern. There are other details into which we cannot here enter, but which support the See also:interpretation put upon these facts, i.e. that these particular albinoes are carrying in the See also:soma the pattern determinants simultaneously with the absence of some of the factors for pigmentation. Not only do albinoes thus carry the determinants for pattern, but it has been known for some time that they also carry gametic-ally, but never visible somatically, the determinants for either the ferment or the chromogen for one or more See also:colours. L. Cuenot was the first to show this for albino mice. He was able by appropriate experiments to demonstrate that when an albino is derived (extracted) from a coloured ancestry, and is then crossed with a coloured individual, both the colour of the pigmented parent and of the pigmented ancestry of the albino may appear among the individuals of the offspring. Immediately subsequent to Cuenot, G. M. Allen in America demonstrated the same fact upon the same species of rodents. C. C. Hurst, more recently, has shown that albino rabbits. whether pure bred for eight generations at least, or extracted from pigmented parents, may carry the determinants for black or for black and grey. In this latter case the determinants for black are carried by See also:separate gametes from those carrying grey, and the two kinds of sex-cells exist in approximately equal See also:numbers. This is likewise true of albino mice when they carry the determinants for more than one colour. Since Hurst's See also:work, L., Doncaster and G. P. Mudge have both shown that albino rats also carry in a latent condition the determinants for black or grey. The experiments of the latter author show that, if a gametically pure black rat be crossed with an albino derived from a piebald black and white ancestry, all the offspring in successive litters will be black; but if the same black parent be crossed with albinoes extracted from parents of which one or both are grey, then both grey and black members will appear in the successive litters. The proportions in which the various coloured individuals appear are approximately those demanded by the Mendelian principle of gametic purity and segregation. Cuenot and Hurst have also shown that when albinoes of one colour extraction are crossed with albinoes of another colour extraction the segrega, tion of the colour determinants in the gametogenesis of the albinoes takes place in precisely the same way that it does in the gametogenesis of a pigmented individual; that is, in Mendelian See also:fashion. Or, to See also:express it otherwise, an albino extracted from yellow parents, bred with an albino extracted from black parents, will give an albino offspring whose gametes in equal numbers are bearers of the black and yellow determinants. And when one of these albinoes is bred with a pure coloured individual, a mixed offspring will appear in the first See also:generation. Some of the individuals will be one or other of the two colours, the determinants of which were borne by the albino, and others the colour of the pigmented parent. But in such albino crosses the colour characters are latent because albinoes do not carry the whole of the complements for colour See also:production. They carry only some determinant or determinants which are capable of developing colour when they interact with some other determinant or determinants carried alone by pigmented individuals. Whether albinoes carry the tyrosinase or other ferment, or whether they carry the chromogen or chromogens, is not yet settled. Miss Durham's work suggests that they carry the latter. But that they never bear both is proved by the fact that, when albinoes are crossed with each other, none but albinoes ever result in the offspring. One apparent exception to this See also:rule only is known, and this almost certainly was due to See also:error. It is not only among albino animals that colour factors are carried in a latent condition, but also in white See also:flowers. W. See also:Bateson has shown this to be the case for the sweet-See also:pea (Lathyrus odoratus), See also:var. Emily See also:Henderson, and for certain white and cream See also:stocks (Matthiola). When white Emily Henderson (the race having See also:round See also:pollen grains) is crossed with a blue-flowered pea, See also:purple offspring result. Similarly, when white Emily Henderson (long pollen grains) is crossed with white Emily Henderson (round pollen grains), the offspring wholly consists of the reversionary purple type, and sometimes wholly of a red bicolor form known as " Painted See also:Lady." : These two types never appear in the same See also:family. With the stocks, when a white-flowered and hairless form is crossed with a cream-flowered and hairless one, all the offspring are purple and hairy. Bateson considers that the purple colour is due to the simultaneous existence in the plant of two colour factors which may be designated by C and R. If either one of these two is absent the plant is colourless. Cream-coloured flowers are regarded as white because cream is due to yellow plastids and not to See also:sap colour. Thus the cream plant may carry C and the white one R. When they are crossed the two factors for colour production are brought together. Obviously, we may regard C as a tyrosinase and R as a chromogen, or vice versa; and in the case of the white sweet-pea crossed with a blue-flowered one, and producing purple offspring, we may imagine that the white See also:flower brought in an additional tyrosinase or a chromogen not present in the blue. flower, which, when combined or mixed with the chromogen or tyrosinase for blue, gave purple. A similar explanation may apply to C. Correns's experiment, in which he crossed white Mirabilis See also:jalapa with a yellow form, and always obtained red-flowered offspring. In heredity, complete albinism among animals is always recessive; and partial albinism (piebald) is always recessive to complete pigmentation (self-coloured). When an albino mouse, rat, guinea-See also:pig or rabbit is crossed with either a pure self or pure pied-coloured form, the offspring are similar to, though not always exactly like, the coloured parent; provided, of course, that the albino is pure and is not carrying some colour or pattern determinant which is dominant to that of the coloured parent used. No albinoes, in such a case, will appear among the first generation, but if the individuals of this (F.r) generation are crossed inter se or back crossed with the albino parent, then albino individuals reappear among the offspring. In the former case they would form one-See also:quarter of the individuals of this second (F.2) generation, and in the latter, one-See also:half. The recessive nature of albinism and its See also:distribution in Mendelian fashion is almost certainly as true for man as for lower forms. This has been shown by W. C. Farabee for negroes in Coanoma See also:county, See also:Mississippi. The facts are as follows. An albino See also:negro married a normal negress. They had three See also:children,all See also:males. All three sons married, and two of them had only normal children, judged of course by somatic characters. But the third son married twice, and by the first wife had five normal and one albino children, and by the second, six normal and three albino children. If we assume that the two negresses which the third son married were themselves carrying albinism recessive —an exceedingly probable condition considering that albino negroes are not uncommon—the result is accurately in accordance, as W. E. Castle has shown, with Mendelian expectation. For there is expected in the offspring of this third son coloured individuals and albinoes in the proportion of 3:1. There is actually 1i:4, which is the nearest possible approximation with the number rs. The operation of Mendelian processes in human heredity is further shown by the See also:close relationship that exists between the appearance of albinoes and See also:cousin marriages. An albino is a homozygote; that is, all its gametes are carrying the character of albinism and none of them bear the alternative character —the allelomorph—of pigmentation. By pigmentation is here meant all those factors which go to its production. Now such a gametic (See also:egg or sperm) constitution can only result when two individuals, all or some of whose gametes are pure with regard to the character albinism, meet in fertilization. Hence it is readily seen that it is among cousin marriages that the greater probabilities exist that two individuals bearing identical characters will meet, than in the See also:population at large. This can be illustrated in the following See also:scheme. Let A stand for a pure albino and (A)N for a normal See also:person, who nevertheless carries the character albinism (A) recessive. Then, in the scheme below, if Ab and (A)Nb are two brothers who both marry normal wives N, their children N(A) in the first case will be all normal in appearance but will be carrying albinism recessive; and in the second case some will be pure normal individuals N, and some will be like the children of the first See also:brother, i.e. N(A). Now, if one of these latter children of the second brother marries a cousin—a See also:child of the first brother,—their offspring, if large enough, will consist 'of some pure normals N, impure normals N(A), and of albinoes A. AbXN (A) Nb x N N(A) N(A) +N N+2N(A)+A No other rational explanation of the close relationship between albinism and cousin marriages is at present forthcoming. And, when the whole facts are borne in mind, there can be no reason-able doubt that the Mendelian principles offer an intelligible solution of the problem. A popular conception exists that albinoes are less constitutionally strong than the pigmented individuals of the same species. In support of this belief there is more or less scientifically ascertained evidence. Conversely, there is, however, conclusive evidence that in some instances and in respect of certain qualities the opposite belief is true.
To See also:deal with the former belief first, we have the remarkable case cited by See also: And with certain cutaneous diseases accompanied by constitutional disturbances which afflict cattle, the See also:affection in the skin appears on the patches bearing white hairs, the other parts remaining apparently healthy. Such cases suggest that we should be more correct in regarding, not albinism as correlated with constitutional defects, but rather pigmentation as correlated with See also:powers of See also:immunity or increased resistance against certain injurious processes. In the See also:West Indies '"the only horned cattle See also:fit for work are those which have a good deal of black in them; the white are terribly tormented by the insects and they are weak and sluggish in proportion to the black." Coming to man, it is known that some albino negroes are peculiarly sensitive to the bites of insects; and with Europeans it is a generally observed fact that the fairer individuals are more seriously affected by the bites of fleas and bugs than are darker ones. Dr See also:Twining, in the British• Association Reports for X845, p. 79, cites some instances described by See also:Humboldt, who says that the See also:copper-coloured natives of the high See also:plain of Bogoto, and at a lower level on the Magdalena See also:river, were generally See also:free from See also:goitre. Professor Poffig, also cited by Dr Twining, states that on the See also:east side of the See also:Andes in See also:Chile, in some of the races which live there, he did not see a single case of goitre, and yet in the white inhabitants, who live exactly as the natives, it prevails in a great degree. Turning now to instances of the opposite kind, it is known that silkworms which spin colourless cocoons are more resistant to the attacks of a certain deadly fungus than are those which spin the yellow ones. In some parts of North America it is found that the white peaches are much less liable to the attack of a disease known as the "yellows" than are the yellow-fleshed ones. In the region of the Mississippi, Farabee has observed that the albino negroes are taller and broader than the black-skinned individuals. We may assume that increased stature and breadth imply some sort of inherent See also:physical superiority, 'and if such an See also:assumption is valid we have in man evidence that albinism is correlated not with constitutional defectiveness but with greater perfectness. But the question as to whether albinoes are more or less constitutionally vigorous than pigmented individual, of the same species may be tested by exact measurement. In ' 1893 W. D. Halliburton and T. G. See also:Brodie, in ascertaining the physiological properties ' of nucleo-proteids, found that when they were intravascularly injected into pigmented rabbits, coagulation of the blood resulted, but of the eight albinoes which they used, none clotted. At a subsequent period (1897) Halliburton and J. W. See also:Pickering showed that the three synthesized colloids of Grimaux in the same way produced coagulation in pigmented animals, but failed to do so in albinoes. Pickering, still later, showed, in the case of four Norway hares, two of which were injected while in their pigmented or summer coat, and two while in their albino or winter coat, that coagulation occurred in the former cases but not in the latter. Quite recently, however, the author of this article has made a more detailed examination of the question, operating upon several hundreds of rabbits. And he found that all albinoes do not fail to See also:clot when intravascularly injected with nucleoproteids. Only about 9 % of them thus failed absolutely to manifest any trace of coagulation. But about 7 % showed an exceedingly limited coagulation, in which the clot was colourless and flocculent, and confined to the See also:heart. The rest gave a typical and more or less wide-spread coagulation. Moreover, it was found that all the failures of coagulation occurred when the nucleo-proteid used was obtained from pigmented animals. Wheit it was derived from albinoes no failures occurred. Allpigmented animals dotted when the nucleo-proteid was derived from either source. The Himalayan rabbits reacted like complete albinoes, and x 2 % of them failed to clot when injected with nucleo-proteid extracted from pigmented animals. The interesting fact was thus ascertained that allalbihoes are not alike. To students of heredity this is precisely what would have been expected. For, as the facts above described show, albinoes, though apparently identical externally, are yet the See also:carriers of different hereditary characters. Among albino rats, for instance, the author of this article has reason to believe, upon theoretical grounds resting on an experimental basis, that probably no less than thirteen types exist. With rabbits and mice there must be a still larger number. In the intravascular coagulation experiments above described, all the rabbits were carefully weighed, and the amount of nucleoproteid injected until coagulation occurred was measured. This would give for albinoes and pigmented individuals the amount per kilogramme of body-See also:weight required to kill in each case, and would afford a measurement of the relative resistance of the two races. It was found that the resistance of albinoes towards the coagulative effects of injected nucleo-proteids was to that of pigmented individuals as 1.5 to 1.0. In this case, the greater constitutional vigour of the albino is thus accurately demonstrated. But it does not necessarily follow that with other materials and with other constitutional qualities the state of things would not be reversed. One other feature remains to be mentioned. Albinism appears, in the processes of heredity, to be sometimes indissolubly correlated with certain peculiar traits. It is well known that the long-haired albino rabbit, called See also:Angora, when at rest, has the See also:habit of swaying its head sideways in a peculiar fashion. C. C. Hurst has shown that the long-haired and albino characters are always accompanied in heredity with the swaying habit. The Angora character never occurs without it. xvii. (New See also:York) ; " Mendel's See also:Law of Heredity," See also:Science, N.S. vol. xviii. (New York) ; W. E. Castle and G. M. Allen, " Mendel's Law and the Heredity of Albinism," Proc. Amer. Acad. Arts and Sci. vol. xxxviii. ; L. Cuenot, " L'heredite de la pigmentation chez !es souris," See also:Arch. d. Zool. Exper. et Gen. Notes et Revue, See also:ser. 3, tom. to, and ser, 4, tom. I and z ; Charles Darwin, Variation of Animals and Plants under Domestication, vols. i. and ii., 2nd ed. (See also:London, 1899); L. Doncaster, " See also:Inheritance of Coat Colour in Rats," Proc. Camb. Phil. See also:Soc. vol. xiii. (Camb., 1906); V. von Ducceschi, Rendiconti della R. Accad. dei Lincei, vol. ii.; Archivio di Fisiologia, vol. i.; Florence M. Durham, " Tyrosinases in the Skins of Pigmented Vertebrates," Proc. See also:Roy. Soc. vol. lxxiv.; W. C. Farabee, "Notes on Negro Albinism," Science, N.S. vol. xvii. (New York) ; Furth v. Schneider, Beitr. z. Chem. Phys. u. Path. Bd. 1; W. Haacke, " Ueber Wesen, Ursachen and Vererbung von Albinismus and Scheckung, &c.," Biol. Centralbl. Bd. 15; Halliburton and Brodie, Journ. Phys. Camb. and See also:Land. vols. xiv., xvi., xvii., xviii. ; Halliburton and Pickering, Journ. Phys, vol. xviii. ; C. C. Hurst, " Experimental Studies on Heredity in Rabbits," Journ. Lin. Soc. Zool. vol. See also:xxix. ; Geo. P. Mudge, Intravascular Coagulation and Albinism, Preliminary See also:Note," Proc. Phys. Soc., 1905; Packard, See also:Memoirs of See also:National See also:Academy of Sciences (1888) ; Pickering, Journ. Phys. vols. xviii. and xx.; E. B. Poulton, Colour of Animals (Lend., 189o); Twining, Brit. Assoc. Reports, 1845; H. M. See also:Vernon, Variation in Animals and Plants (London, 1903) ; F. H. Welch, " Winter Coat in Lepus americanus, " Proc. Zool. Soc., 1869. (G. P. Additional information and CommentsThere are no comments yet for this article.
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