Special embryonic organs may attain a great prominence; normal embryonic phases may be slurred over, or perhaps extinguished. It is often hard to say what is ancestral, what acquired, to distinguish between structures which may be inherited or independently evolved.

General works. H. Milne Edwards, Lecons sur la physiologie et l'anatomie comparee de l'homme et des animaux, Paris, 14 vols. 1857-81. Gegenbaur, Grundriss der Vergleich. Anatomie, Leipzig, 1878, transl. by F. J. Bell, revised by E. Ray Lankester as 'Elements of Comparative Anatomy,' London, 1878. Claus, Grundziige der Zoologie, ed. 4, Marburg, 1880-2. Traite de Zoologie, Claus, transl. by Moquin-Tandon, ed. 2, Paris, 1884. Textbook of Zoology, Claus, transl. by Sedgwick, London, 2 vols. 1884-5. Hayek, Handbuch der Zoologie, Vienna, 3 vols. 1885-87. Schmarda, Zoologie, Vienna, 2 vols. 1877-8. Pagenstecher, Allgemeine Zoologie, Berlin, 4 parts, 1875-81. The Various 'Suites a Buffon.'

Embryology. F. M. Balfour, Comparative Embryology, 2 vols., London, 1880-81. A. C. Haddon, An Introduction to the Study of Embryology, London, 1887.

Distribution. A. R. Wallace, Geographical Distribution, 2 vols., London, 1876. Id., Island Life, London, 1880.

Practical Manuals. A. M. Marshall and C. H. Hurst, A Junior Course of Practical Zoology, London, 1887. T. J. Parker, A Course of Instruction in Zootomy (Vertebrata), London, 1884. Carl Vogt and Emile Yung, Traite d'anatomie compared pratique, Paris, 1882 (incomplete). W. K. Brooks, Handbook of Invertebrate Zoology for Laboratories and Sea-side Work, Boston, 1882. T. H. Huxley and H. B. Martin, A course of Elementary Instruction in Practical Biology, ed. 4, London, 1877. G. B. Howes, Atlas of Practical Elementary Biology, London. 1885.

Bibliography. Zoological Record, London, from i. 1864, onwards. Zoologischer Jahresbericht, edited from the Zoological Station at Naples, Berlin, 1879 and onwards. Jahresberichte uber die Fortschrifte der Anatomie und Physiologie, Hoffman and Schwalbe, Leipzig, i. 1873 and onwards. Lists in the Zoologischer Anzeiger, i. 1878, and onwards. The Berichte in vol. ii. of the yearly issues of the Archiv fur Naturgeschichte, commencing with the issue for 1836. Royal Society's Catalogue of Scientific Papers, 1800-1863, London, 6 vols., 1867-72; second series, for period 1864-73, 2 vols., London, 1877-9. L. Agassiz, Bibliographia Zoologiae et Geologiae, edited by Strickland and Jardine, 4 vols., London, Ray Society, 1848-54. Biblio-theca Zoologica, Carus and Engelmann, works from 1846-60, 2 vols., Leipzig, 1861; Continuation under same title, works from 1861-80, O. Taschenberg, vol. i. issued. D'Arcy Thompson, Bibliography of Protozoa, Sponges, Coelenterata, Worms, Polyzoa, Brachiopoda, and Tunicata, 1861-83, Cambridge, 1885. The various catalogues of the Natural History Department of the British Museum. For Insecta, see Hagen, Bibliotheca Entomologica, 2 vols., Leipzig, 1862-3.

Palaeontology. Zittel, Handbuch der Palaeontologie, Abth. 1, Palaeozoologie, vols. i. and ii. on Non-Vertebrates, complete; vol. iii. on Vertebrata, commenced, Miinchen and Leipzig. Quenstedt, Handbuch der Petrefactenkunde, ed. 3, Tubingen, 1885. Caps, vi, vii, viii of Wallace's 'Distribution,' supra, for distribution of extinct animals. Fossils in relation to strata, Part II of Phillip's Manual of Geology, ed. by Seeley and Etheridge, London, 1885.

Bibliography of Palaeontology. Geological Record, Whitaker and Dalton, 1874-78; the lists and summaries in the Zoological Record, the Zoologischer Jahresbericht (supra), and the Neues Jahrbuch fur Mineralogie, Geologie, and Palaeontologie, Stuttgart.