Page:EB1911 - Volume 16.djvu/49

Rh recalling the Acrasieae. From each cyst ultimately emerges a single amoeba, or more rarely four (figs. 6, 7). The saprophyte Diplophrys (?) stercorea (Cienk.) appears closely allied to this.

Chlamydomyxa (W. Archer) resembles Labyrinthula in its freely branched plasmodium, but contains yellowish chromatophores, and minute oval vesicles (“physodes”) filled with a substance allied to tannin—possibly phloroglucin—which glide along the plasmodial tracks. The cell-body contains numerous nuclei; but in its active state is not resolvable into distinct oval amoeboids. It is amphitrophic, ingesting and digesting other Protista, as well as “assimilating” by its chromatophores, the product being oil, not starch. The whole body may form a laminated cellulose resting cyst, from which it may only temporarily emerge (fig. 2), or it may undergo resolution into nucleate cells which then encyst, and become multinucleate before rupturing the cyst afresh.

Leydenia (F. Schaudinn) is a parasite in malignant diseases of the pleura. The pseudopodia of adjoining cells unite to form a network; but its affinities seem to such social naked Foraminifera as Mikrogromia.

See Cienkowsky, Archiv f. Microscopische Anatomie, iii. 274 (1867), xii. 44 (1876); W. Archer, ''Quart. Jour. Microscopic Science'', xv. 107 (1875); E. R. Lankester, Ibid., xxxix., 233 (1896); Hieronymus and Jenkinson, Ibid., xiii. 89 (1899); W. Zopf, Beiträge zur Physiologie und Morphologie niederer Organismen, ii. 36 (1892), iv. 60 (1894); Pènard, Archiv für Protistenkunde, iv. 296 (1904); F. Schaudinn and Leyden, Sitzungsberichte der Königlich preussischen Akademie der Wissenschaft, vi. (1896).

 LAC, a resinous incrustation formed on the twigs and young branches of various trees by an insect, Coccus lacca, which infests them. The term lac (laksha, Sanskrit; lakh, Hindi) is the same as the numeral lakh—a hundred thousand—and is indicative of the countless hosts of insects which make their appearance with every successive generation. Lac is a product of the East Indies, coming especially from Bengal, Pegu, Siam and Assam, and is produced by a number of trees of the species Ficus, particularly F. religiosa. The insect which yields it is closely allied to the cochineal insect, Coccus cacti; kermes, C. ilicis and Polish grains, C. polonicus, all of which, like the lac insect, yield a red colouring matter. The minute larval insects fasten in myriads on the young shoots, and, inserting their long proboscides into the bark, draw their nutriment from the sap of the plant. The insects begin at once to exude the resinous secretion over their entire bodies; this forms in effect a cocoon, and, the separate exudations coalescing, a continuous hard resinous layer regularly honeycombed with small cavities is deposited over and around the twig. From this living tomb the female insects, which form the great bulk of the whole, never escape. After their impregnation, which takes place on the liberation of the males, about three months from their first appearance, the females develop into a singular amorphous organism consisting in its main features of a large smooth shining crimson-coloured sac—the ovary—with a beak stuck into the bark, and a few papillary processes projected above the resinous surface. The red fluid in the ovary is the substance which forms the lac dye of commerce. To obtain the largest amount of both resin and dye-stuff it is necessary to gather the twigs with their living inhabitants in or near June and November. Lac encrusting the twigs as gathered is known in commerce as “stick lac”; the resin crushed to small fragments and washed in hot water to free it from colouring matter constitutes “seed lac”; and this, when melted, strained through thick canvas, and spread out into thin layers, is known as “shellac,” and is the form in which the resin is usually brought to European markets. Shellac varies in colour from a dark amber to an almost pure black; the palest, known as “orange-lac,” is the most valuable; the darker varieties—“liver-coloured,” “ruby,” “garnet,” &c.—diminish in value as the colour deepens. Shellac may be bleached by dissolving it in a boiling lye of caustic potash and passing chlorine through the solution till all the resin is precipitated, the product being known as white shellac. Bleached lac takes light delicate shades of colour, and dyed a golden yellow it is much used in the East Indies for working into chain ornaments for the head and for other personal adornments. Lac is a principal ingredient in sealing-wax, and forms the basis of some of the most valuable varnishes, besides being useful in various cements, &c. Average stick lac contains about 68% of resin, 10 of lac dye and 6 of a waxy substance. Lac dye is obtained by evaporating the water in which stick lac is washed, and comes into commerce in the form of small square cakes. It is in many respects similar to, although not identical with, cochineal.  LACAILLE, NICOLAS LOUIS DE (1713–1762), French astronomer, was born at Rumigny, in the Ardennes, on the 15th of March 1713. Left destitute by the death of his father, who held a post in the household of the duchess of Vendôme, his theological studies at the Collège de Lisieux in Paris were prosecuted at the expense of the duke of Bourbon. After he had taken deacon’s orders, however, he devoted himself exclusively to science, and, through the patronage of J. Cassini, obtained employment, first in surveying the coast from Nantes to Bayonne, then, in 1739, in remeasuring the French arc of the meridian. The success of this difficult operation, which occupied two years, and achieved the correction of the anomalous result published by J. Cassini in 1718, was mainly due to Lacaille’s industry and skill. He was rewarded by admission to the Academy and the appointment of mathematical professor in Mazarin college, where he worked in a small observatory fitted for his use. His desire to observe the southern heavens led him to propose, in 1750, an astronomical expedition to the Cape of Good Hope, which was officially sanctioned, and fortunately executed. Among its results were determinations of the lunar and of the solar parallax (Mars serving as an intermediary), the first measurement of a South African arc of the meridian, and the observation of 10,000 southern stars. On his return to Paris in 1754 Lacaille was distressed to find himself an object of public attention; he withdrew to Mazarin college, and there died, on the 21st of March 1762, of an attack of gout aggravated by unremitting toil. Lalande said of him that, during a comparatively short life, he had made more observations and calculations than all the astronomers of his time put together. The quality of his work rivalled its quantity, while the disinterestedness and rectitude of his moral character earned him universal respect.

His principal works are: Astronomiae Fundamenta (1757), containing a standard catalogue of 398 stars, re-edited by F. Baily (Memoirs Roy. Astr. Society, v. 93); Tabulae Solares (1758); Coelum australe stelliferum (1763) (edited by J. D. Maraldi), giving zone-observations of 10,000 stars, and describing fourteen new constellations; “Observations sur 515 étoiles du Zodiaque” (published in t. vi. of his Éphémérides, 1763); Leçons élémentaires de Mathématiques (1741), frequently reprinted; ditto de Mécanique (1743), &c.; ditto d’Astronomie (1746), 4th edition augmented by Lalande (1779); ditto d’Optique (1750), &c. Calculations by him of eclipses for eighteen hundred years were inserted in L’Art de vérifier les dates (1750); he communicated to the Academy in 1755 a classed catalogue of forty-two southern nebulae, and gave in t. ii. of his Éphémérides (1755) practical rules for the employment of the lunar method of longitudes, proposing in his additions to Pierre Bouguer’s Traité de Navigation (1760) the model of a nautical almanac.

See G. de Fouchy, “Éloge de Lacaille,” ''Hist. de l’Acad. des Sciences'', p. 197 (1762); G. Brotier, Preface to Lacaille’s Coelum australe; Claude Carlier, Discours historique, prefixed to Lacaille’s Journal historique du voyage fait au Cap (1763); J. J. Lalande, Connoissance des temps, p. 185 (1767); ''Bibl. astr. pp. 422, 456, 461, 482; J. Delambre, Hist. de l’astr. au XVIIIe siècle'', pp. 457-542; J. S. Bailly, ''Hist. de l’astr. moderne, tomes ii., iii., passim; J. C. Poggendorff, Biog.'' Lit. Handwörterbuch; R. Grant, ''Hist. of Physical Astronomy, pp. 486, &c.; R. Wolf, Geschichte der Astronomie''. A catalogue of 9766 stars, reduced from Lacaille’s observations by T. Henderson, under the supervision of F. Baily, was published in London in 1847.

 LACAITA, SIR JAMES [] (1813–1895), Anglo-Italian politician and writer. Born at Manduria in southern Italy, he practised law in Naples, and having come in contact with a number of prominent Englishmen and Americans in that city, he acquired a desire to study the English language. Although a moderate Liberal in politics, he never joined any secret society, but in 1851 after the restoration of Bourbon autocracy he was arrested for having supplied Gladstone with information on Bourbon misrule. Through the intervention of the British and Russian ministers he was liberated, but on the publication