II. CHEMISTRY.

(E. B. P.)

Colours displayed in Courtship, Secondary Sexual Characters, Epigamic Colours.-Darwin suggested the explanation of these appearances in his theory of Sexual Selection (The Descent of Man, London, 1874). The rivalry of the males for the possession of the females he believed to be decided by the preference of the latter for those individuals with especially bright colours, highly developed plumes, beautiful song, &c. Wallace does not accept the theory, but believes that natural selection, either directly or indirectly, accounts for all the facts. Probably the majority of naturalists follow Darwin in this respect. The subject is most difficult, and the interpretation of a great proportion of the examples in a high degree uncertain, so that a very brief account is here expedient. That selection of some kind has been operative is indicated by the diversity of the elements into which the effects can be analysed. The most complete set of observations on Epigamic display was made by George W. and Elizabeth G. Peckham upon spiders of the family Attida (Nat. Hist. Soc. of Wisconsin, vol. i., 1889). These observations afforded the authors "conclusive evidence that the females pay close attention to the love-dances of the males, and also that they have not only the power, but the will, to exercise a choice among the suitors for their favour." Epigamic characters are often concealed except during courtship; they are found almost exclusively in species which are diurnal or semi-diurnal in their habits, and are excluded from those parts of the body which move too rapidly to be seen. They are very commonly directly associated with the nervous system; and in certain fish, and probably in other animals, an analogous heightening of effect accompanies nervous excitement other than sexual, such as that due to fighting or feeding. Although there is Epigamic display in species with sexes alike, it is usually most marked in those with secondary sexual characters specially developed in the male. These are an exception to the rule in heredity, in that their appearance is normally restricted to a single sex, although in many of the higher animals they have been proved to be latent in the other, and may appear after the essential organs of sex have been removed or become functionless. This is also the case in the Aculeate Hymenoptera when the reproductive organs have been destroyed by the parasite (Stylops). Cunningham has recently argued (Sexual Dimorphism in the Animal Kingdom, London, 1900) that secondary sexual characters have been produced by direct stimulation due to contests, &c., in the breeding period, and have gradually become hereditary, a hypothesis involving the assumption that acquired characters are transmitted. Wallace suggests that they are in part to be explained as "Recognition Characters," in part as an indication of surplus vital activity in the male.

AUTHORITIES.—The following works may also be consulted :EIMER. Orthogenesis der Schmetterlinge. Leipzig, 1898.-POULTON. The Colours of Animals. London, 1890.-BEDDARD. Animal Coloration. London, 1892.-HAASE. Researches on Mimicry (translation). London, 1896.- WALLACE. Natural Selection and Tropical Nature. London 1895. Darwinism.

The coloration of the surface of animals is caused either by pigments, or by a certain structure of the surface by means of which the light falling on it, or reflected through its superficial transparent layers, undergoes diffraction or other optical change. Or it may be the result of a combination of these two causes. It plays an important part in the relationship of the animal to its environment, in concealment, in mimicry, and so on; the presence of a pigment in the integument may also serve a more direct physiological purpose, such as a respiratory function. The coloration of birds' feathers, of the skin of many fishes, of many insects, is partially at least due to structure and the action of the peculiar pigmented cells known as "chromatophores" (which Garstang defines as pigmented cells specialized for the discharge of the chromatic function) and is much better marked when these have for their background a "reflecting layer" such as is provided by guanin, a substance closely related to uric acid. Such a mechanism is seen to greatest advantage in fishes. Among these, guanin may be present in a finely granular form, causing the light falling on it to be scattered, thus producing a white effect; or it may be present in a peculiar crystalline form, the crystals being known as "iridocytes"; or in a layer of closely apposed needles forming a silvery sheet or mirror. In the iris of some fishes the golden red colour is produced by the light reflected from such a layer of guanin needles having to pass through a thin layer of a reddish pigment, known as a "lipochrome." Again, in some lepidopterous insects a white or a yellow appearance is produced by the deposition of uric acid or a nearly allied substance on the surface of the wings. In many animals, but especially among invertebrates, colouring matters or pigments play an important rôle in surface coloration; in some cases such coloration may be of benefit to the animal, but in others the integument simply serves as an organ for the excretion of waste pigmentary substances. Pigments (1) may be of direct physiological importance; (2) they may be excretory; or (3) they may be introduced into the body of the animal with the food.

Of the many pigments which have been described up to the present time, very few have been subjected to elementary chemical analysis, owing to the great difficulties attending their isolation. An extremely small amount of pigment will give rise to a great amount of coloration, and the pigments are generally accompanied by impurities of various kinds which cling to them with great tenacity, so that when one has been thoroughly cleansed, very little of it remains for ultimate analysis. Most of these substances have been detected by means of the spectroscope, their absorption bands serving for their recognition, but mere identity of spectrum does not necessarily mean chemical identity, and a few chemical tests have also to be applied before a conclusion can be drawn. The absorption bands are referred to certain definite parts of the spectrum, such as the Fraunhofer lines, or they may be given in wave-lengths. For this purpose the readings of the spectroscope are reduced to wave-lengths by means of interpolation curves; or if Zeiss's microspectroscope be used, the position of bands in wave-lengths (denoted by the Greek letter A) may be read directly. Examples of the absorption bands yielded by colouring matters will be found in Ency. Brit. vol. xx. p. 483.

Hæmoglobin, the red colouring matter of vertebrate blood, C8H1203N195S,FeO218, and its derivatives hæmatin, C32H80N FeO3, and hæmatoporphyrin, C1H1N2O, are

4

colouring matters about which we possess definite chemical knowledge, as they have been isolated, purified, and analysed. Most of the bile pigments of mammals have likewise been isolated and studied chemically, and all of these are fully described in the text-books of physiology and physiological chemistry. Hæmoglobin, though physiologically of great importance in the respiratory process of vertebrate animals, is yet seldom used for surface pigmentation, except in the face of white races of man or in other parts in monkeys, &c. In some worms the transparent skin allows the hæmoglobin of the blood. to be seen through the integument, and in certain fishes also the hæmoglobin is visible through the integument. It is a curious and noteworthy fact that in some invertebrate animals in which no hæmoglobin occurs, we meet with its derivatives. Thus hæmatin is found in the so-called bile of slugs, snails, the limpet, and the crayfish. In sea-anemones there is a pigment which yields some of the decomposition - products of hæmoglobin, and associated with this is a green pigment apparently identical with biliverdin (C16H18N2O4), a green pigment. Again, hæmatoporphyrin is found in the integuments of star-fishes and slugs, and occurs in the "dorsal streak" of the earth-worm (Lumbricus terrestris), and perhaps in other species. Hæmatoporphyrin and biliverdin also occur in the egg-shells of certain birds, but in this case they are derived from hæmoglobin. Hæmoglobin is said to be found as low down in the animal kingdom as the Echinoderms, e.g., in Ophiactis virens, and Thyonella gemmata. It also occurs in the blood of Planorbis corneus, and in the pharyngeal muscles of other mollusca.

bile

In

A great number of other pigments have been described; for example, in the muscles and tissues of animals, both vertebrate and invertebrate, are the histohæmatins, of which a special muscle pigment, myohæmatin, is one. vertebrates the latter is generally accompanied by hæmoglobin, but in invertebrates-with the exception of the pharyngeal muscles of the mollusca-it occurs alone. Although closely related to hæmoglobin or its derivative hæmochromogen, the histohæmatins are yet totally totally distinct, and they are found in animals where not a trace of hæmoglobin can be detected. Another interesting pigment is turacin, which contains about 7 per cent. of nitrogen, found by Professor Church in the feathers of the Cape lory and other plantain-eaters, from which it can be extracted by water containing a trace of ammonia. It has been isolated, purified, and analysed by Professor Church. From it may be obtained turacoporphyrin, which is identical with hæmatoporphyrin, and gives the band in the ultra-violet which Soret and subsequently Gamgee have found to be characteristic of hæmoglobin and its compounds. Turacin itself gives a peculiar two-banded spectrum, and contains about 7 per cent. of copper in its molecule. Another copper-containing pigment is hæmocyanin, which in the oxidized state gives a blue colour to the blood of various mollusca and arthropoda. Like hæmoglobin, it acts as an oxygen-carrier in respiration, but it takes no part in surface coloration.

A class of pigments widely distributed among plants and animals are the lipochromes. As their name denotes, they are allied to fat and generally accompany it, being soluble in fat solvents. They play an important part in surface coloration, and may be greenish, yellow, or red in colour. They contain no nitrogen. As an example of a lipochrome which has been isolated, crystallized, and purified, we may mention carotin, which has recently been found in green leaves. Chlorophyll, which is so often associated with a lipochrome, has been found in some Infusoria, and in Hydra and Spongilla, &c. In some cases

it is probably formed by the animal; in other cases it may be due to symbiotic algae, while in the gastric gland of many Mollusca, Crustacea, and Echinodermata, it is derived from food-chlorophyll. Here it is known as entero-chlorophyll. The black pigments which occur among both vertebrate and invertebrate animals often have only one attribute in common, viz., blackness, for among the discordant results of analysis one thing is certain, viz., that the melanins from vertebrate animals are not identical with those from invertebrate animals. The melanosis or blackening of insect blood, for instance, is due to the oxidation of a chromogen, the pigment produced being known as a uranidine. In some sponges a somewhat similar pigment has been noticed. Other pigments have been described, such as actiniochrome, echinochrome, pentacrinin, antedonin, polyperythrin (which appears to be a hæmatoporphyrin), the floridines, spongioporphyrin, &c., which need no mention here; all these pigments can only be distinguished by means of the spectroscope.

Most of the pigments are preceded by colourless substances known as 'chromogens," which by the action of the oxygen of the air and by other agencies become changed into the corresponding pigments. In some cases the pigments are built up in the tissues of an animal, in others they appear to be derived more or less directly from the food. Derivatives of chlorophyll and lipochromes especially, seem to be taken up from the intestine, probably by the agency of leucocytes, in which they may occur in combination with, or dissolved by, fatty matters and excreted by the integument. In worms especially, the skin seems to excrete many effete substances, pigments included. No direct connexion has been traced between the chlorophyll eaten with the food and the hæmoglobin of blood and muscle. Attention may, however, be drawn to the work of Dr Schunck, who has shown that a substance closely resembling hæmatoporphyrin can be prepared from chlorophyll; this is known as phylloporphyrin. Not only does the visible spectrum of this substance resemble that of hæmatoporphyrin, but the invisible ultra-violet also, as recently shown by Mr C. A. Schunck.

The reader may refer to Schäfer's Text-Book of Physiology (1898) for Gamgee's article "On Hæmoglobin, and its Compounds"; to the writer's papers in the Phil. Trans. and Proc. Roy. Soc. from 1881 onwards, and also Quart. Journ. Micros. Science and Journ. of Physiol.; to Krukenberg's Vergleichende physiologische Studien from 1879 onwards, and to his Vorträge. Miss Newbigin has collected in Colour in Nature (1898) most of the recent literature of this subject. Dr Schunck's papers will be found under the heading "Contribution to the Chemistry of Chlorophyll" in Proc. Roy. Soc. from 1885 onwards; and Mr C. A. Schunck's paper in Proc. Roy. Soc. vol. lxiii. (C. A. MACM.)

Columbia, capital of Boone county, Missouri, U.S.A., situated in 38° 57′ N. lat. and 92° 19′ W. long., in the central part of the state, on the Wabash Railway, at an altitude of 783 feet. It is the site of the State University, and of Christian and Stephens Female Colleges. Population (1880), 3326; (1890), 4000; (1900), 5651.

Columbia, a borough of Lancaster county, Pennsylvania, U.S.A., situated on the east bank of Susquehanna river, in the south-eastern part of the state, on branches Railways, at an altitude of 251 feet. of the Pennsylvania and the Philadelphia and Reading It has extensive manufactures, principally of iron. Population (1880), 8312; (1890), 10,599; (1900), 12,316.

Columbia, capital of Richland county, South Carolina, U.S.A., and of the state, situated in 34° 00' N. lat. and 80° 57′ W. long. on the east bank of Congaree river, at the junction of the Saluda and Broad, near the centre of the state, at an altitude of 244 feet.

Five railways enter it, namely, the Atlantic Coast Line, the Southern, the South Carolina, and Georgia, the Florida Central and Peninsula, and the Columbia, Newberry, and Laurens. It is the seat of South Carolina College, which in 1898 had twelve professors and 188 students. Population (1880), 10,036; (1890), 15353; (1900), 21,108.

Columbia, capital of Maury county, Tennessee, U.S.A., situated on Duck river, in the central part of the state, at an altitude of 646 feet. It has two railways, the Louisville and Nashville and the Nashville, Chattanooga, and St Louis. Population (1880), 3400; (1890), 5370; (1900), 6052.

Columbia, District of. See WASHINGTON.

Columbia University, in the city of New York, U.S.A., includes both a college and a university in the strict sense of the word as used in the United States. It com

prises the faculties of law, medicine, philosophy, political science, pure science, and applied science. It is the successor of the corporation known as "The Governors of King's College, in the Province of New York," founded in 1754 by royal charter. In the educational system is also included Barnard College for Women, a separate corporation founded in 1889, and a teachers' college, also a separate corporation. In 1897 the university moved from the centre of the city northwards to Morningside Heights, which overlook the Hudson from an altitude of 150 feet. The Medical School (the College of Physicians and Surgeons) remains in its old location opposite Roosevelt Hospital. The entire plant of the university represents a cost of about $9,500,000. In the year ending 30th June 1900 the expenditures for educational purposes were $942,460, leaving a deficiency of $17,328, which was met by a special guarantee fund. In 1901 there were registered in the college for men (Columbia) 475 students, and in the college for women (Barnard) 293 students, making a total of 768 undergraduates. The total of non-professional graduate students was 412. The scientific schools contained 539 students, the law school 422 students, the medical school 775 students, the teachers' college 498 students-making a total of 2234 professional students. The total number of students in the university was thus 3830 (including 417 summer session students). In addition to these there were 29 auditors and 679 members of extension courses, making a grand total of 4538. The number of teachers of all grades for the same year was 375. The library, which numbers about 300,000 volumes, is thoroughly modern, and is selected with special reference to scholarly The university is growing in all departments. (See also UNIVERSITIES and EDUCATION.)

uses.

(s. L*.)

Columbus, capital of Muscogee county, Georgia, U.S.A., situated on the western boundary of the state, at an altitude of 260 feet, on Chattahoochee river, which is navigable to this point. Just above the city the river crosses the fall line, producing falls and rapids which furnish excellent water-power. This has been turned to account in extensive cotton manufactures. Three railways enter the city, the Southern, the Central of Georgia, and the Georgia and Alabama. Population (1880), 10,123; (1890), 17,303; (1900), 17,614.

Columbus, capital of Bartholomew county, Indiana, U.S.A., situated on the east fork of White river, a little south of the centre of the state, at an altitude of 629 feet. It is at the intersection of lines of the Pittsburg, Cincinnati, Chicago, and St Louis and the Cleveland, Cincinnati, Chicago, and St Louis Railways. The centre of population of the United States was in 1900 very near this place. Population (1880), 4813; (1890), 6719; (1900), 8130.

Columbus, capital of Lowndes county, Mississippi, U.S.A., at the intersection of the Southern and the Mobile and Ohio Railways, on the Tombigbee river. It contains large cotton mills. Population (1890), 4559; (1900, with limits enlarged), 6484, including 3366 negroes.

Columbus, capital of Franklin county, Ohio, U.S.A., and of the state of Ohio. The site was purposely selected in 1813 near the centre of the state, in 39° 57′ N. lat. and 82° 59′ W. long., at an altitude of 743 feet, the elevation of the lines at the Union Station. It is a railway centre of the first importance. Fourteen different lines of railway, belonging to eight companies, enter the fine new Union Station in the heart of the city, thence radiating in all directions. The manufactures employed in 1890 a capital of $16,178,703, with 13,421 hands and an output of $22,887,586. The principal manufacture was that of carriages and waggons, valued second, with a value of $2,139,185. Then followed the at $3,199,287. Foundry and machine-shop products were

manufacture of steam cars, the product of which was valued at $1,670,078. The Ohio State University, situated here, had in 1898 a faculty of 95 professors, and was attended Its by 1150 students, one-fifth of whom were women. property was valued at $2,600,000, and its income at $292,000. It has schools of law, medicine, dentistry, pharmacy, and veterinary surgery. Capital University, a Lutheran institution, also here, had in 1898 a faculty of 10 teachers and 113 students. The death-rate in 1899 was but 10.83 per thousand; this is less than half the average of American cities, and little more than half that of the Union. The assessed valuation of property, real and personal, was, in 1899, $64,344,990. The income from all sources was $2,612,301, the expenditure $2,570,038, and the net debt $6,059,146. The tax rate per $1000 was $27.50. Population (1880), 51,647; (1890), 88,150; (1900), 125,560; death-rate (1900), 15.8.

Combaconum, or Kumbakonam, a city of British India, in the Tanjore district of Madras, in the delta of the Kaveri; with a railway station on the South Indian Railway, 194 miles from Madras. In 1881 it had a population of 50,098, and in 1891 of 54,307, of whom nearly one-fifth were Brahmans. In 1901 the population was 59,688, showing an increase of 10 per cent. The municipal income in 1897-98 was Rs.80,480. It contains a Government college, two high schools, four printingpresses, and a reading-room.

intro

Combinatorial Analysis.-The Combinatorial Analysis, as it was understood up to the end of the 18th century, was of limited scope and restricted application. P. Nicholson, in his Essays on the Historical Combinatorial Analysis, published in 1818, states that "the Combinatorial Analysis is a branch of mathematics which teaches us to ascertain and exhibit all the possible ways in which a given number of things may be associated and mixed together; so that we may be certain that we have not missed any collection or arrangement of these things that has not been enumerated." Writers on the subject seemed to recognize fully that it was in need of cultivation, that it was of much service in facilitating algebraical operations of all kinds, and that it was the fundamental method of investigation in the theory of Probabilities. Some idea of its scope may be gathered from a statement of the parts of algebra to which it was commonly applied, viz., the expansion of a multinomial, the product of two or more multinomials, the quotient of one multinomial by another, the reversion and conversion of series, the theory of indeterminate equations, &c. Some of the elementary theorems and various particular problems appear in the works of the