The thyroid is a paired gland, and lies close to the origin of the common carotid arteries. The thymus is also paired, and may be found in young birds as a long gland, one on each side of the neck. The spleen lies on the right side of the proventriculus. The supra-renal capsules are two yellow bodies closely connected to the iliac veins at the anterior end of the kidneys.

The generative system is the same as in all birds. A rudiment of the right ovary is rarely detectable; but there is frequently a rudiment of the oviduct of that side. There is no intromittent organ.

Birds; W. K. Parker and A. Newton, Encyclopaedia Britannica (9th ed.), iii. Aves, Selenka and Gadow, Bronn's Klas. und Ordn. des Thierreichs, vi. Abth. iv. (in progress).

Points in Anatomy of Columbae, Garrod, P. Z. S. 1874.

Columba livia. Yarrell, History of British Birds, 4th ed. by Newton and Saunders, iii. p. 13; or Seebohm, British Birds and their Eggs, ii. p. 405.

Pigeon. T. J. Parker, Zootomy, London, 1884, p. 209.

Integument. General account, Jeffries, Proc. Nat. Soc. Boston, xxii. 1882-83. Skin of foot. Hanau, Inaugural Dissertation, Bonn, 1881. Epitrichium and beak. Gardiner, A. M. A. xxiv. 1884. Feathers. Studer, Inaugural Dissertation, Berne, 1873. Id. Z. W. Z. xxx. 1878. Waldeyer, Festgabe zu Jacob Henle, Bonn, 1882. Pterylography. Nitsche, Ray Society, 1867 (transl. by Sclater). Uropygial gland. Kossmann, Z. W. Z. xxi. 1870-71. Cutaneous sense organs. Merkel, Endigungen der sensibeln Nerven, Rostock, 1880; cf. Carriere, A. M. A. xxi. 1882.

Central nervous system, Stieda, Z. W. Z. xix. 1867.

Special Sense Organs

Eye.Leuckart, Grafe and Samisch, Handbuch der Augenheilkunde, Leipzig, 1876, ii. p. 144. Pecten. Denissenko, A. M. A. xix. 1881. Crampton's muscle. Exner, SB. Akad. Wien. lxxxviii. Abth. 3, 1882. Harderian gland. MacLeod, Archives de Biol. i. 1880. Ear. Hasse, Z. W. Z. xvii. 1867. Retzius, Gehororgan der Wirbelthiere, ii. Stockholm, 1884.

Alimentary canal. Gadow, J. Z. xiii. 1879 (Columbae, p. 148). Salivary glands. Reichel, M. J. viii. 1882. Glands of Proventriculus. Nussbaum, A. M. A. xiii. 1877 (p. 744). Gizzard. Wiedersheim, A. M. A. viii. 1872. Bursa Fabricii. Forbes, P. Z. S. 1877. Retterer, Journal de l'Anatomie (Robin), xxi. 1885. Cf. Martin Saint-Ange, Etude de l'appareil reproducteur, Paris, 1854 (Memoires pre-sentds par divers savants, etc. a l'Acade'mie des Sciences, Paris, xiv. 1856). Histology of oesophagus and proventriculus. Klein, Stricker's Histology (Sydenham Soc), i. p.

535, P-554

Syrinx.Variations of vocal organs in Passeres, J. Muller, transl. by Bell, Oxford, 1878. Of Ratitae. Forbes, P. Z. S. 1881.

Trachea, Convolutions of: Forbes, P. Z. S. 1882.

Lungs.Aeby, Bronchialbaum der Saugethiere, etc, Leipzig, 1880, p. 93. Minute Anatomy, Schultze, Stricker's Histology (Sydenham Soc), ii. p. 68. In Apteryx, Huxley, P. Z. S. 1882.

Air-sacs.Strasser, M. J. iii. 1877. Campana, Recherches d'Anatomie, etc Anatomie de l'appareil pulmonaire, etc, chez le poulet, Paris, 1875. Milne Edwards, Lecons sur la Physiologie, etc. ii. p. 531.

Heart.Sabatier, Le Coeur, Paris, 1873. Right auriculo-ventricular valve, etc, Gegenbaur, J. Z. ii. 1866, p. 375. Arterial system. Barkow, Meckel's Archiv f. Anat. u. Physiol. 1829. Carotid arteries. Garrod, P. Z. S. 1873. Venous system. Neugebaur, Nova Acta, xxi. 1845. Points in venous system. Wade, J. L. S. xii. 1876. Renal-portal system. Jourdain, A. Sc. N. (4), xii. 1859.

Lymph hearts.Stannius, Archiv. f. Anat. u. Physiol. 1843; in the chick, Budge, same Archiv, Anat. Abth. 1882.

Thymus.Afannassiew, A. M. A. xiv. 1877, p. 346.

Kidney.Heidenhain, A. M. A. x. 1874, p. 20. Hufner, Zur Vergleich. Anat. u. Physiol. der Harnkanalchen, Dissertation, Leipzig, 1866.

Oviduct.Blasius, Z. W. Z. xvii. 1867. Albumen glands (also of Amphibia), Loos, Z. W. Z. xxxv. 1881.

On the mechanism of flight. See Garrod, P. Z. S. 1875, and in Anat. of Passerine Birds, with 4 Plates, P. Z. S. 1876. Strasser, J. Z. xix. 1885. Marey, Animal Mechanism (Internat. series), xi. 1874. Pettigrew (same series), vii. 1874; and Trans. Roy. Soc. Edinburgh, xxvi. 1872.

On muscles of wings. Schopss, Meckel's Archiv f. Anat. u. Physiol. 1829. Sundevall, Brit. Ass. Reports, 1855. Rolleston, Homology of Muscles of Shoulder Joint, Tr. L. S. xxxi. 1870 (cf. a paper by Furbringer, M. J. i. 1876). Garrod, P. Z. S. 1873 and 1874. Fiirbringer, M. J. xi. 1885.

On muscles of hinder extremities. Garrod, P. Z. S. 1873 and 1874. Gadow, Zur Vergleich. Anat. der Muskulatur des Beckens, etc. der Ratiten, Jena, 1880.

Value of innervation in determining homology of a muscle. Furbringer, J. Z. vii. 1873, p. 240. Cunningham, Journal of Anat. and Physiol, xvi. 1882.