128 



The T 



oLirna 



of Heredity 



however, that a siniihir condition has 

 been found in other wihl species makes 

 such an assumption seem hkely. 



It is impossible to state whether 

 the different sporadic appearances are 

 due to independent mutations or 

 whether they all trace back to an orig- 

 inal mutative change which has been 

 carried down through the various 

 ramifications of descent and into the 

 many breeds of the present time. There 

 appears to be no evidence of the char- 

 acter appearing in stock known to be 

 homozygous for normal feathers, but 

 on the other hand cases where such a 



condition coukl be asserted must l)e 

 \ery rare. On the i)asis of what is 

 known of the occurrence of mutative 

 changes at present, it seems most 

 probable that the large preponderance 

 of cases of sporadic appearance of silky 

 plumage are siinply due to the chance 

 mating of birds carrying the silky 

 factor in heterozygous condition. The 

 occasional recurrence of the mutation 

 de novo is, howe\er, not improbable, but 

 e\'en so, it could of course not become 

 \isible in effect until two indi\iduals 

 both carrying it should come to- 

 gether. 



Vol. 1. Verlag von 

 Pp. xvi+3Q4. 



Bibliography 



1894 Batesox, W. Materials for the Study of Variation. Macmillan and Co., Lond. & X.V. pp. 



xv-f598. 

 1908 Batesox. W. and Punnett, R. C. Poultry. Reports to the Evolution Committee of the Royal 



Society. Report IV. Pp. 1-60. 



1908 Beeck, .\. Die Federviezucht als Wirtschaftlichsweg und Liebhaberei. 

 Richard Carl Schmidt & Co. Pp. .xiii-880. 



186.S Bement, C. X. The .American Poulterer's Companion. Harper & Bros. 



1911 Brehm's "Tierleben." Leipzig und Wien. Zweiter Band. Pp. viii+491. 

 1914 Bo.NHOTE, J. Lewis. Preliminary Notes on the Heredity of Certain Characters in a Cross between 



Silky and Yokohama Fowls. Cairo Scientific Journal, Vol. 8; no. 91. .\pr. Pp. 8.5-89. 



1912 Cu.N.M.NCHAM, J. T. Mcndelian K.\periments on Fowls. Proc. of the Zool. Soc. of London. I; 

 Jan.-June, Pp. 1-504. 



1868 Darwin, Charles, .\nimals and Plants under Domestication. \ol. 2. John Murray, London. 

 Pp. viii+486, 1st edition. 



1906 Dave.nport, C. B. Inheritance in Poultry. Carnegie Publication no. .S2. Pp. v-f-l.?6. Seven- 

 teen plates. 



1907 Davenport, C. B. Heredity and Mendel's Law. Proc. of the Washington .\cademy of Sci. 

 Vol. 9, July .31, pp. 179-188. 



1913 Robinson, John H. Our Domestic Birds. Ginn & Co. Pp. x-|-317. 



1909 Stirges, Rev. T. W. The Poultry Manual. Macdonald & Evans. Pp. .\viii+.S97. 



1910 Taibert, Franz. Untersuchungen iiber die Ursachen der Seiden und WoUfederbildungbei 

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1873 Tegetmeier, W. B. The Poultry Book. George Rutledge & Sons, London. Vyi. xiii-f-.390. 

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Menschenzucht, 



Kisch. P|)- I'JO, kart., preis M. 7. 

 A. Marcus and K. Webers' Verlag, 

 I^onn, dermany, 1920. 



In this brief book apparentl\- in- 

 tended for adolescents. Dr. Kisch has 

 succeeded in gi\ing a remarkably good 

 and scnsil)lc outline of social hygiene. 



An Introduction to Social Hygiene 

 \-on Dr. Franz His chapter headings are "The Ripen- 



ing of Lo\e," "The Wonder of Crea- 

 tion," "Here<lil\' and Selection," "Fer- 

 tility," "Children Outside of Marriage," 

 and "Marriage." A liook in Knglish 

 covering similar groiuul and written in 

 a similar imsentimental and matter-of- 

 fact tone would be well worth while. — 

 I'. V. 



