The

fertilization by the fish-culturists. Salmonida have always occupied their chief interest.

The centers of such hybridization have been the experiments of Sir James Maitland at Howietoun recorded by Day and those of Seth Green of the New York hatchery, cited below and further recorded by R. B. Roosevelt in Proc. Amer. Assoc. Adv. Science, 1884, vol. 33, pp. 510-515.

Miscellaneous and unimportant items. Baird, S. F. 1873.18; Green, S. 1879.2, 1880.2,.4; Grieg, J. A. 1906.1; Hallock, C. 1873.5; Mather, F. 1876.6; Rasch, H. H. 1867.2; Smith, E. V. 1915.1; Anon. 387.

Experiments of Sir J. R. Gibson-Maitland at Howietoun, near Stirling, Scotland. Day, F. 1884.6, 1885.5,.8, 1887.1, 1888.1, 1890.1. - Notice of this work. Behrens, G. 1885.1.

List of hybrid forms, all reared to maturity unless otherwise stated:

Oncorhynchus tschawytscha (milt) × Salvelinus fontinalis (eggs). Four-year old females developed eggs too large to void and evidently infertile. Green, S. 1882.1; Roosevelt, R. B. 1880.1, 1881.1.

Oncorhynchus sp. X Oncorhynchus sp. Crosses between various species, fry only. Richardson, J. A. 1906.1.

Salmo salar X Salmo fario. Infertile hybrids produced at Hüningen, Alsace. Arens, C. 1894.1; Haack, H. 1880.6, 1894.1. - at Winkelsmühle near Düsseldorf. Overbeck, G. 1880.2.- Review of these experiments. Leuckart, C. G. 1882.1, .2. Three-year old hybrids developed eggs, in similar cross of Lochleven trout (eggs) and salmon. Day, F. 1882.4, 1885.8.

Salmo fario X Lota marmorata. By artificial fertilization. Fraas, C. N. 1854.1.

Salmo fario X Salvelinus fontinalis. Lochleren trout eggs with brook trout milt. Hybrids fertile. Day, F. 1882.9, 1884.6, 1885.8.

Salmo fario (including Trutta lacustris) X Salvelinus salvelinus. This cross first produced at Bärau near Gmunden, Austria. Kner, R. 1865.4. Produced at various localities in Germany and Russia. Arens, C. 1893.1; Haacke, J. W. 1893.1;

Knoch, J. Add. 1884.1. - Salmo schiffermülleri Bloch, (Silberlachs) because of similarity of bred examples, considered a sterile hybrid possibly of this cross. Fitzinger, L. J. 1875.1. 1876.1.

Salmo fario X Salvelinus umbla. Crossed in France. Bruyant, C. 1910.1; Crettiez, J. 1906.1. This hybrid rec'd at U. S. Nat. Museum from Norway. Bean, T. H. 1889.20, Add. 1889.1.

Salmo irideus × Salvelinus fontinalis. Sterile hybrids. Zalsman, P. G. 1914.1. Supposed hybrids from Wytheville station. Bean, T. H. Add. 1889.1.

umbla.

Salmo irideus X Salvelinus Rainbow trout eggs fertilized with milt of Ombre-chevalier. Crettiez, J. 1906.1.

Salvelinus alpinus X Salvelinus fontinalis. Scotch charr milt and Amer. charr eggs. Hybrids fertile but second hybrid

cernua.

Salmo fario X Lota marmorata. Through artificial fertilization. Fraas, C. N. 1854.1. Perca fluviatilis X Acerina Found in nature and also produced by artificial fertilization. Kammerer, P. 1907.2.

Gobio fluviatilis X Leuciscus phoxinus. Knauthe, K. 1891.1.

Chanobryttus gulosus X Lepomis gibbosus. Radcliffe, L. 1914.1.

Heros facetus X Geophagus gymnogenys. Schütz, R. 1912.1.

For hybrids between pike (Esox lucius) and pickerel (E. reticulatus), see G. C. Embody, in Journ. Hered. 1918, vol. 9, pp. 253-256, 2 pls. Also O. W. Smith, "The Book of the Pike," 1922, pp. 185–189.

ICHTHYOLOGY

For histories of natural sciences including ichthyology, see Historical matter.

1910.3;

Historical accounts. Essays on the history of ichthyology. Boulenger, G. A. Cuvier, G. & Valenciennes, A. 1828.1 (vol. 1); Günther, A. C. 1910.1; Jordan, D. S. 1902.5. Reprinted in 1905.1; ★Lönnberg, A. J. 1901.5. Development of American ichthyology. Gill, T. N. 1904.8; Goode, G. B. 1884.2, 1888.2; Lockington, W. N. 1882.2.

Works of a general nature

For compendia, dictionaries, encyclopedias, natural histories, works of a popular or nontechnical nature relating to fishes, etc., see the section entitled General works on natural history.

For treatises on the fauna of a definite region, see the desired locality under Fauna of the world.

General works of a technical or precise nature: introductory studies, guides to studies, etc.

Text in English. Boulenger, G. A. 1895.2, 1904.7; ★Bridge, T. W. 1904.1; Dean, B. 1895.4; Gill, T. N. 1881.1, 1896.18, Add. 1881.1; Goode, G. B. 1888.1, 1903.1; Girard, C., Suckley, G. & Agassiz, L. 1857.1; ★Goodrich, E. S.

Ichthyology-Cont'd.

1900.1; Griffith, E. 1834.1; Günther, A. C. 1859.1, 1880.4, 1894.2, 1902.1; Jones, T. 1847.1; Jordan, D. S. 1905.1, 1907.1; Monro, A. 1785.1, 1787.1; Richardson, J. 1856.1; Ward, Samuel, 1770.1, 1775.1, 1776.1; Wilson, J. 1838.1,.2.

Text in French. Ajasson de Grandsagne, J. B. 1828.1-1829.2; Auboin, S. 1831.1; ★Bloch, M. E. 1782.1, 1785.1,.2, 1786.1, 1801.1; Bonnaterre, J. P. 1788.1; Buffon, G. L. 1803.1; Castel, R. L. 1801.1; ★Cuvier, G. & Valenciennes, A. 1827.1, 1828.1; Daubenton, L. J. 1782.1; Duméril, A. M. 1856.2; Duméril, A. H. 1865.3; Goüan, A. 1770.1; ★Lacépède, B. G. 1795.1, 1798.1, 1803.1, 1819.2, 1844.1, 1878.1; Sauvage, H. E. 1865.1; Sonnini de Manoncourt, C. N. 1803.1; ★Valenciennes, A. 1837.1, 1850.1.

Text in German. Bechstein, J. M. 1797.1; Favaro, G. 1908.1; ★Favaro, G. & Mozejko, B. 1913.1; Gmelin, C. C. 1829.1; Goüan, A. 1781.1; Günther, A. 1886.2; Haempel, O. 1912.1; Heppe, J. C. 1782.1, 1800.1; Lacépède, B. G. 1799.3, 1833.1; ★Lönnberg, A. J. 1901.5; Minding, J. 1832.1; Schinz, H. R. 1836.1; Schmid, K. 1822.1.

Text in Latin. Broussonet, P. M. 1782.1; Goüan, A. 1770.1; Walbaum, J. J. 1788.1; Wulff, J. C. 1765.1.

Earlier works on ichthyology, in PreLinn. section. ★Aldrovandi, U. 1613.1; ★Artedi, P. 1738.1; ★Belon, P. 1551.1, 1553.1; Bodin, J. 1555.1; Boussuet, F. 1558.1; ★Gesner, C. 1556.1, 1558.1. 1563.1; Giovio, P. 1524.1, 1527.1; Klein, J. T. 1740.1; Rondelet, G. 1554.1; ★Salviani, H. 1554.1; ★Willughby, F. 1686.2; Anon. 734, 757, 764.

For the fish symbol in art, see under Mythology and Symbolism.

See also Archæology, for ancient fish paintings, carvings, etc.

General collections. Bloch, M. E. 1786.1, 1787.1; Blumenbach, J. F. 1797.1; Buc'Hoz, P. J. 1782.1; Kielsen, F. C. 1836.1; Lacépède, B. G. 1819.1; Richardson, J. 1843.2; Reichenbach, A. B. 1838.1; Rosenthal, F. 1812.1; Schmidt, K. 1820.1; Strack,-1819.1; Swainson, W. 1820.1; Wagner, R. 1841.1; Anon. 503. from Cuvier's Animal Kingdom." Comte, J. A. 1832.1; Guérin-Méneville, F. E. 1830.1.

Plates

Bur

Atlases, Wall Charts, etc. Biological and zoological charts. meister, H. C. 1860.1; Fitzinger, L. 1864.1; Howes, G. B. 1885.1; Keibel, F. 1909.1; Leuckart, C. & Nitsche, H. 1877.1; M'Alpine, D. 1881.1; M'Alpine, D. & M'Alpine, A. N. 1880.1; Marshall, W. A. 1898.2; Schmeil, O. 1905.1.

Zittel's "Wandtafeln." Fossil Selachians and Ganoids. Pompeckj, J. F. 1900.1; Zittel, K. A. 1900.1.

Austrian and German fishes. Redlefgmal, E. 1909.1; Schreiber, 1913.1; Anon 386.

Fishing scenes. Refs. in Pre-Linn. seetion. Barlow, F. 1671.1; Bol, J. 1600.1; Coenen, A. 1577.1; Cornelius, G. 1662.1; Laan, A. 1700.1; Lonicer, J. A. 1582.1; Meulen, S. 1700.1.

Fishes of specific regions Asia. Illustrations of Indian zoology. Gray, J. E. 1830.1. Collections of Chinese fish paintings by native artists. Reeves, J. 1828.1; Anon. 135. -Japanese fishes. Anon. 742. "Dorades de la Chine." Martinet, F. N. Add. 1780.1.

European fishes from Austria and Germany. Redlefgmal, E. 1909.1; Meidinger, C. 1785.1; Weber, J. C. 1851.1; Anon. 771; Baldner, L. Pre-Linn. 1666.1.

British fishes. Whymper, C. 1897.1; Haecken, A. Pre-Linn. 1734.1. Scandinavian. Kroyer, H. N. 1847.1. Italian fishes. Salviani, H. Pre-Linn. 1554.1.

North American fishes. Agassiz, L. Baird, S. F. 1889.1; Kilbourne, S. & Goode, G. Add. 1879.1.

South American fishes, chiefly Brazilian. Wallace, A. R. [n. d.] (Rio Negro). Pre-Linn. section. Marcgrave, G. 1643.1; Mentzel, C. 1660.1; Post, F. 1643.1.

Commentaries on Marcgrave's figures of Brazilian fishes. Lichtenstein, M. H. 1818.1; Martius, C. F. 1853.1; Schneider, J. G. 1786.1.

South Sea fishes. - Fishes collected by J. Banks. Broussonet, P. Add. 1782.1. Sketches made during Capt. James Cook's third voyage. Ellis, W. W. Add. 1776.1. East Indian Fishes, Pre-Linn. refs., Bruyn, C. 1718.1; Renard, L. 1718.1; Hooge, R. 1680.1; Anon. 773.

West Indian fishes. Pre-Linn. section. Catesby, M. 1750.1; Gautier d'Agoty, J. 1752.1; Hooge, R. 1680.1; Plumier, C. 1695.1. Identification of Catesby's figures. Jordan, D. S. 1885.4. INTEGUMENT OR SKIN (OF FISHES)

Although the integument properly includes the denticles and bony scales formed within the dermis, for the sake of convenience, the present section is limited to the soft tissues of the integument. The hard parts are treated under the heading " Dermal skeleton.'

Likewise references to certain structures derived from the epidermis will be found elsewhere, such as Phosphorescent organs under Luminosity, and Poison glands under Poisonous fishes.

The integument in fishes, as in all vertebrates, consists of two layers, an outer epidermis (Oberhaut) consisting of the modified ectoderm, and an inner dermis or corium (Cutis vera, Lederhaut) composed of the outer or superficial layer of the mesenchyme which is modified mesoderm.

The dermis in fishes is thin and presents few distinctive features. It has in consequence not While been the subject of extensive study. many of the following references include the structure of the dermis, in general they refer chiefly to the epidermis.

In the blind fish Typhlogobius, there is "a highly abnormal development of bloodvessels in the sub-epidermal portion of the integument" obscuring the pigment layer and giving the living fish a pink color. This condition is presumably for the purpose of cutaneous respiration. Ritter, W. E. 1893.1.

No true metamerism is shown in the skin, such resemblances are due to muscular stresses. Grosser, O. 1905.1..

Transplantation of patches of skin from the uncolored ventral surface to the colored dorsal surface and vice versa in Nemachilus show no changes in color of the transplanted area until later immigration of chromatophores from surrounding areas and resorption takes place. Sécerov, S. 1912.1.

The skin of Anguilla, like other glandular structures, undergoes an excitatory variation as a result of electrical, thermic, and mechanical stimulation. Reid, E. W. 1894.2; Reid, E. W. & Tolputt, A. G. 1894.4.

Cutaneous sensory papillæ

In the blind fishes (Amblyopsida), the lack of eyes is compensated by the great development, especially on the head, of the cutaneous sensory papillæ. ★Eigenmann, C. H. 1909.2.

Although possessing eyes, the Gobiida likewise possess an extraordinary development of such cutaneous papillæ, whose arrangement is said by Sanzo to be of diagnostic value. ★Sanzo, L. 1911.1; Winther, G. P. 1874.4.

Nerve terminations in the epidermis. Fusari, R. 1901.1, 1907.1; Jobert, C. & Grandey, 1870.1; ★Merkel, F. 1880.1; Retzius, M. G. 1892.4,.5; Schöler, E. 1885.1; Schulze, F. E. 1892.1.

For the epidermal sense organs (Hautsinnesorgane), see End organs under Senses and sense organs.

THE EPIDERMIS

The epidermis consists of two layers, a lower thick layer of actively dividing cells, the stratum of Malphigi and an outer layer of protective cells, the stratum corneum, which to replace wear is constantly renewed by division of the cells in the lower or Malphigian layer.

In various amphibians and reptiles this outer layer (periderm) is periodically shed as a whole but no such process occurs in fishes.

The most comprehensive general treatise (in German) on the epidermis, with a full bibliography is Studnička, F. K. 1909.1.

Other older general treatises in German, are Leydig, F. 1879.1, and Maurer, F. 1895.1.

Probably the best summary in English of the literature on the epidermis of fishes is given in Reid, E. W. 1894.3.

Glandular elements

In correlation with their aquatic environment and in order to reduce surface friction by the secretion of mucus or "slime," the epidermis of fishes is generally rich in unicellular glandular structures.

Leydig (F. 1851.1), according to Reid (E. W. 1894.3), first demonstrated the possibility of a secretory process in the fish skin by the description of specialized cells in the epidermis of some twelve genera of fishes. To these cells he gave the general term "schleimzellen." Subsequent research has shown that several varieties were included under this general term.

"Kolben" or club cells

The first of the elements subsequently delimited was the Kolben" cell or Kolbenformige Gebilde of Max Schultze (1861.2) of the epidermis in Petromyzon. By F. E. Schulze (Add. 1867.1) the "kolben" cells were shown to occur also in Tinca, Leuciscus, Cobitis, Anguilla, Esox, and Silurus, and by Fritsch (G. T. 1886.1) in Malapterurus. These are the club cells of authors ("clavate" cells of Wright, R. R. 1884.1. p. 254). Schultze thought the "kolben cells to be of the nature of nervous end organs and possibly contractile, because of certain appearances in polarized light, resembling those of striated muscle fibre. Although this view has been upheld by Pogojeff (L. 1889.1), nearly all subsequent workers have agreed on their secretory nature. Fættinger (A. 1876.1) followed their actual extrusion. The careful experimental work of Reid (E. W. 1894.3) on Anguilla, clearly demonstrates that the "club cells produce the fine granules in the slime and also the threads, which are homologous with and resemble the threads in the slime of Myxine but are of finer texture.

The most comprehensive treatise on the Kolben cells, with a table showing the fishes in which they occur or are absent is Oxner, M. 1905.1.

Becherzellen " or goblet cells

The second form of secretory cell is the goblet or Becherzell. Although known as the

Integument - Cont'd.

"Vesicula limpida " of the intestinal epithelium by Henle as early as 1837, the "Becherzellen " were first adequately described by Schulze (F. E. Add. 1867.1). The name " Becherzellen was first applied by this author in the "Centralbl. f. med. Wiss.," no. 11, 1866. These cells occur in the epidermis of fishes and amphibians, the intestinal epithelium of all vertebrates, and in the respiratory canal" of lung breathers. The Becherzellen " receive adequate treatment (bibliographic, historical, etc.) by J. H. List in the Arch. f. mikr. Anat., 1886, vol. 27, pp. 481-588, 6 pls.

According to the researches of Reid (E. W. 1894.3), the goblet cells supply the mucin and after reaching the surface and discharging their load, they are capable of undergoing regeneration.

The club cells, the goblet cells, and the ordinary epidermic cells, are descendants of the palisade cells of the basal layer of the epidermis.

Papers specifically relating to the goblet cells are List, J. H. 1885.1-.3; Helly, K. 1905.1; Oedmannson, 1863.1; Oeffinger, H. 1867.1.

Epidermis in general

The following papers in general refer to the histological structure of the epidermis including the club and goblet cells and other epidermal elements.

Epidermis of Petromyzon. Fættinger, A. 1876.1; Kapelikin, V. 1897.1; Kölliker, R. A. 1860.6; Leuckart, C. G. 1856.1; Loewenthal, N. 1904.1; Marenghi, G. 1903.1; Müller, H. 1864.1,.2; Pogojeff, L. 1889.1; Razzauti, A. 1911.1, 1912.1; Schultze, M. J. 1861.2; Schulze, F. E. 1863.1, Add. 1867.1; Studnička, F. K. 1909.1.

Structure of the epidermis in Protopterus. Kölliker, R. A. 1860.1; Paulson, O. M. 1865.1.

Thread cells of Myxine

The hagfish or "slime eel," Myxine glutinosa, derived its specific name from its well known habit of exuding enormous quantities of mucus. According to Blomfield (J. E. 1882.1), "two individuals thrown into a bucket of water are capable of gelatinising the whole with their secretion.'

This secretion, according to Reid (E. W. 1893.1), is derived from a double row of glands (schleimsäcke of Müller), which are virtually simple involutions of the skin (epidermal inpushings into the dermis), extending along the belly of the animal from head to tail. Each gland has a separate duct to the surface. These structures were first described by Retzius (A. J. 1824.1) but more accurately by Müller (J. 1834.1, v).

The secretion, before its dilution with water, possesses a milky appearance due to the presence of large numbers of cells, whose protoplasm has been converted into a single complexly wound thread which, after exudation, readily unwinds and adds to the viscosity.

These cells, called "Fadenkörper" by Müller, were independently termed "thread cells" by Blomfield. They are apparently specialized forms of the "Kolben" cells, described above, and develop in the epidermal lining of the gland.

Papers relating to the epidermis of Myxine with the thread cells, mucous glands, etc. Blomfield, J. E. 1882.1; Kölliker, R. A. 1860.6; and Retzius, M. G. 1905.1.

Chemical examination of the mucous secretions of Myxine shows granules presenting most of the features of a mucin, but which do not yield a body reducing Fehling's solution. Reid, E. W. 1893.1, 1894.1.

Bdellostoma also encloses itself in a transparent, gelatinous mass having the consistency of thick egg albumen. Ayers, H. 1894.1.

Among such cornifications are the pearl organs,' small tubercles appearing chiefly on the head of various Cyprinide, at breeding time. Leydig, F. 1892.2; Reighard, J. 1903.2, 1904.1, 1910.2.

Similar contact organs found on the scales or fins of the males of some Paciliida at the breeding season, are not purely epidermal but possess an osseous or dermal core. Newman, H. H. 1907.1, 1909.1. The teeth" of the Cyclostomata (lampreys) are cornified epidermal structures. For references, see under Dentition.

Deckplatte. In some embryonic Anamnia, Petromyzon and Amphibia, the outer layer of ectoderm cells may, for a time, be ciliated. The cilia however disappear upon the hardening of the superficial protoplasm of the cells of the stratum corneum to form a so-called cuticula. By Studnička (F. K. 1897.5) this striated cuticular structure is termed "Deckplatte."

In Lepadogaster, the epidermis of the adhesive disk forms a thick cuticular plate. Guitel, F. 1888.1; Studnička, F. K. 1906.1, 1909.1.

THE ARGENTEUM

Underlying the dermis or corium of fishes is a layer of connective tissue, the tela subcutanea. In many fishes, this layer contains numerous crystals of guanin which form a reflecting layer composing the argenteum which produces the silvery coloration.

According to Ewald and Krukenberg (1883.1), quoted from Cunningham and MacMunn (1893.1, p. 782), the guanin is contained in connective tissue cells, in some cases in fine crystalline plates as a lime compound (guaninkalk) (Teleostei, Ganoidei, Cyclostomata), in others in the pure condition, and then it is only dead white, and has no metallic lustre (skin of Selachians)." The presence of guanin likewise frequently gives a silvery appearance to the peritoneum and the air bladder. beautiful metallic appearance of the iris in fishes is due to crystals of guanin."

"The

The discovery of the true nature of the guanin is due to Barreswil (Add. 1861.1) who upon making a chemical examination of the "blanc d'ablette " or silvery substance extracted from the skin of the bleak (Alburnus) and used in the manufacture of artificial pearls, decided that this material was identical with

the

'guanin" isolated by Bodo Unger from guano in 1845. A short time later Voit (C. 1865.1) independently reached the same conclusion.

Early investigations on the nature of the silver substance. Goebel, F. 1836.1; Schnitzlein, A. 1836.1, Add. 1837.1; Wittich, W. H. 1854.1.

Distribution of guanin in the skin of fishes. Bethe, A. 1895.1; ★Cunningham, J. T. & MacMunn, C. 1893.1; ★Ewald, A. & Krukenberg, C. F. 1882.1, 1883.1; Prince, E. E. 1893.2; MacMunn, C. A. Add. 1895.1.

For the use of guanin in making artificial pearls, see this heading below Economic products under Fisheries.

Fritsch, G. T. 1894.2; Müller, H. 1852.1. Chimara. Cole, F. J. 1896.1,.2; Collinge, W. E. 1895.2; Reese, A. M. 1910.1; Solger, B. F. 1880.1. Squaloraja. Woodward, A. S. 1887.2. Ganoidei.

Amia. Allis, E. P. 1888.1. Polypterus. Allis, E. P. 1900.1; Baur, G. H. 1896.1; Collinge, W. E. 1893.3, 1896.1. Polyodon. Allis, E. P. 1903.3; A ciNachtrieb, H. F. 1902.1-1912.1.

penser. Baer, K. E. 1826.1; Jaquet, M. 1899.2. -Lepidosteus. Collinge, W. E. 1893.1. - Ganoidei. Collinge, W. E. 1894.1, 1895.5; Kingsbury, B. F. 1896.1. Teleostei. Dantan, L. 1906.1; Leydig, F. 1850.1; Solger, B. F. 1878.2, 1880.1, 1882.2, Add. 1877.2. Muranida. Allis, E. P. 1903.1. - Cottus. Bodenstein, E. 1883.1. - Silurida, chiefly Ameiurus. Bunker, F. S. 1897.1; Fritsch, G. T. (Malopterurus) 1886.1; Herrick, C. J. 1901.1; Pollard, H. B. 1892.1; Wright, R. R. 1884.1. Batrachus. Clapp, C. M. 1899.1; Jordan, D. S. 1900.2. Icosteus. Cohn, L. 1906.1. Gadus. Cole, F. J. 1898.1. Physostomi. Collinge, W. E. 1895.4. Mugil. Fée, F. 1869.1. Lepadogaster. Guitel, F. 1887.2. Cy-Lophius. 1890.1, 1890.2, 1891.1.-Lota. Hyrtl, C. J. 1866.1. Per-Clupea. Ryder, J. A. 1890.3. coids. Steindachner, F. 1862.1 (ii).

Innervation (by branches of the lateralis nerve). Burne, R. H. 1901.1; Leydig, F. 1850.2, 1851.2; Schulze, F. E. 1861.1.

Physiology, or functions, of the lateral line system. Bonnier, P. 1896.1; Knox, R. 1825.1,.2, 1827.1; Lee, F. S. 1898.1; ★Parker, G. H. 1904.1,.2, 1905.1; Stahr, H. 1897.1. Selachii. Fuchs, S. 1895.1,.2. Macrurida. ★Pfüller, A. 1914.1. Cyprinus. Richard, J. 1896.1.

Structure of the lateral line system. Miscellaneous and general. Agassiz, J. L. 1848.6; Beard, J. 1884.1, 1885.1; Dercum, F. 1880.1; Dunn, M. 1895.1, 1901.1; Marsson, M. 1897.2; Sappey, M. P. 1880.1,.2; Vogt, C. C. 1856.1. - Fossil fishes. Collinge, W. E. 1893.2; Woodward, A. S. 1887.7. - Earliest reference. Rivinus, A. Q. Pre-Linn. 1687.1. Larger researches. Allis, E. P. 1904.1; Heilig, K. 1912.1; ★Hofer, B. 1908.1; Hyrtl, C. J. 1843.1; Macdonnell, R. 1864.1; Pell, M. 1907.1; Schulze, F. E. 1870.1, 1871.1.

1889.1.

SENSORY ORGANS

Which are closely associated with
the lateral line

Ampullæ of Lorenzini, mucous canals or subcutaneous pit-organs found on lateral and dorsal surfaces of the heads of Elasmobranchs.

Morphology, development, etc. Boll, F. 1868.1; ★Coggi, A. 1891.2, 1902.1,.2, 1905.1; Brohmer, P. 1908.2; Forssel, G. 1894.1; Johnston, J. B. 1902.5; ★Minckert, W. 1901.1; Peabody, J. E. 1897.1; Retzius, M. G. 1898.3; Rund, G. Add. 1914.1.

As organs for pressure perception. Metcalf, H. E. 1915.1.

Ampullary canals in Chimara. Cole, F. J. 1896.2; Collinge, W. E. 1895.2.

Ampullæ of Savi (Savi's vesicle), of the ventral surface of the head of Torpedo.

Anatomy. Boll, F. 1875.1; Coggi, A. 1891.3; Fritsch, G. T. 1894.2; Garman, S. 1892.4; Kölliker, R. A. 1857.4.

LIVER (INCLUDING GALL BLADDER)

For associated structures, see Intestine and Stomach under Alimentary Tract, also Pancreas and Spleen.

For the occurrence of glycogen in the liver, and for the role of the fat content of the liver of sharks, see under Chemistry.

For urea formation in the liver, see Excretion under Physiology.

Anatomy and morphology, general accounts. Guillot, N. 1846.1, 1848.1; Jones, H. 1854.1; Mierendorff, F. W. 1817.1; Rathke, M. H. 1826.1,.4, 1837.2; Weber, E. H. 1827.8; Schmid, F. C. Add. 1882.1; Shore, T. W. & Jones, H. L. Add. 1889.1.