246 ANIMAL MORPHOLOGY 



decade, has its germ in the work of Mendel, 1 and, in consequence 

 of the stimulating researches of De Vries, 2 Correns, 3 Tschermak, 4 

 Bateson, 5 and others, 6 has developed into a stately doctrine, a 

 doctrine which bids fair to revolutionize biology as the atomic 

 theory did chemistry. It adds at once a new dignity and interest 

 to morphology as well as to the description of species, or taxonomy. 

 In describing the form of an animal we are enumerating its qualities. 

 Many of these are directly the unit characters of the species; others 

 are composite and may be analyzed, by appropriate methods of 

 breeding, into the elemental characteristics. 



I may illustrate this by reference to domesticated poultry, 7 to 

 which I am now paying some attention. It is impossible to enu- 

 merate all of the characteristics of poultry, but the following are 

 some of the most striking : 



Size: Large and dwarf, which are exemplified in the Asiatic 

 breeds and the bantams. 



Colors: Black; buff or red; white; brown (in the female), the 

 male being often bronze, green, black, yellow and white; barred 



1 Mendel's work was first published in Verhandl. naturf. Verein in Briinn, Ab- 

 handlungen, iv, 1865. Published 1866. A translation in English is given by W. 

 Bateson, Mendel's Principles of Heredity, Cambridge [England], 1902. 



2 De Vries (Sur la loi de disjunction des hybrides, Comptes rend, d' Academic des 

 Sciences, Paris, cxxx, 845-847, 1900), and C. Correns (G. Mendel's Regel iiber das 

 Verhalten der Nachkommenschaft der Rassenbastarde, Ber. Deut. Bot. Ges. xvin, 

 158-168, 1900) rediscovered Mendel's paper simultaneously. 



H. de Vries, Ueber erbungleiche Kreuzungen, Ber. Deut. Bot. Ges. xvnr, 435-443 

 (1900) ; Sur les unites des charactires specifiques et leur application a I' etude des 

 hybrides, Rev. gen. de Botanique, xn, 257 (1900); Die Mutationstheorie, Bd. u 

 (1903). 



3 C. G. Correns, Ueber Levkoyen-Bastarde, Zur Kenntniss der Grenzcn der Men- 

 del' schen Rcgcln, Botan. Centralbl. LXXXIV, p. 97 (1900); Ueber Bastarde zwischen 

 Rassen von Zea Mays, Ber. Deut. Bot. Ges. xix, 211 (1901); Bastarde zwischen 

 Maisrassen, Bibliotheca Botanica, Heft 53 (1901); Ueber Bastardirungs-V ersuche 

 mit Mirabilis-Sippen, Ber. Deut. Bot. Ges. xx, 594-608 (1903). 



4 T. E. Tschermak, Ueber kiinstliche Kreuzungbei Pisum sativum, Zeitschr. f. d. 

 Landwirthsch. Versuchswesen,iu, 465-555 (1900); Weitere Beitrdge iiber Verschied- 

 enswerthigkert der Merkmale bei Kreuzung von Erbsen und Bohnen, ibid. IT, 

 641 ff. (1901); Ueber Ziichtung neuer Getreiderassen mittelst kunstlicher Kreuzung, 

 ibid, iv, 1029. Die Theorie der Kryptomerie und des Kryptohybridismus, Bcihefte z. 

 Bot. Centralbl. xvi, 25 pp. (1903); Weitere Kreuzung sstudien an Erbsen, Zeitschrift 

 /. d. Landwirth-Versuchswesen in Oesterr. 106 pp. (1904) . 



5 W. Bateson and E. R. Saunders, Experimental Studies in the Physiology of 

 Heredity, Reports to Evolution Committee of the Royal Society of London, i, 160 

 pp. (1902). 



6 A few important papers may be cited: W. E. Castle and G. M. Allen, 

 The Heredity of Albinism, Proceedings of the American Academy of Arts and 

 Sciences, xxxvm, 601-622 (1903); W. E. Castle, Heredity of Coat Characters in 

 Guinea Pigs and Rabbits. Papers of the Station for Experimental Evolution, 

 -no. 1 (Carnegie Institution of Washington, 1905); C. C. Hurst, Experiments in the 

 Heredity of Peas, Journal of the Royal Horticultural Society of London, xxvm, 

 483-494 (1904); L. Cunot, L'Ph'rfditc de la pigmentation chez les souris, Arch, 

 de Zool. expir. x, notes, 27-30(1902), ibid, i, notes, 33-41 (1903); ibid, n, notes, 

 45-56 (1904). 



7 _ Extensive books have been written on the different races of poultry. The fol- 

 lowing are the most important of those in English: W. B. Tegetmeier, The Poultry 

 Book, London, Routk-dge, 1867; L. Wright, The New Book of Poultry, London, 

 Cassell & Co., 1902; The Poultry Book, New York, Doubleday, Page & Co. 



