370 . EXPEEIMENT STATION KECOED. 



support of his argument. Thus, a silvered variety of guinea pig vp^as produced 

 by systematic selection from a tri-colored race. The silvered area was grad-' 

 ually increased from an individual which had white hairs interspersed with red 

 on the lower side of the body. In experiments with hooded rats, involving 12 

 generations and over 10,000 individuals, the pigmented areas were increased 

 in one series and decreased in another by systematic selection. The view is 

 held that the causes of variability are not necessarily located in the chromo- 

 some of the cell. 



Mendelian proportions and the increase of recessives, F. Ramaley {Amer. 

 'Nat., 46 {1912), No. 546, pi). 3U~351).— This is a study of stable ratios involv- 

 ing Mendelian dominants, heterozygotes, and recessives as exemplified in the 

 inheritance of left-handedness. The author states that the same results will 

 apply to any recessive character when not selected against in mating. Re- 

 cessive characters tend to increase in numbers at the expense of original domi- 

 nant typos if not inherently weak in some respect. 



" These conclusions are reached from a consideration of the following points : 

 (1) The greater ease with which characters may be lost than gained; (2) the 

 great number of combined dominants and heterozygotes which through muta- 

 tion may reach a simpler condition as compared with the small number of 

 recessives and heterozygotes which may be imagined as affording opportunity 

 for mutation to dominance; (3) the more likely survival of recessives in an 

 environment of changing conditions in which now the dominant and now the 

 recessive is hard pressed to maintain its existence." 



Mendel's laws and stock breeding, J. Wilson (Hoard's Dairyman, 42 (1911), 

 No. .'p', P- H^2). — ^An explanation of the principles of Mendelian inheritance so 

 that it can be understood by the stock breeder. 



Mendelism and sex inheritance, E. Rail (Hoard's Dairyman, 43 (1912), No. 

 13, p. 502). — ^A criticism of the article noted above, in which it is maintained 

 that it has not yet been proved that sex is a Mendelian character, and if so 

 would be operative all the time. 



Mendel's law and the occurrence of sex (Farm Poultry, 23 (1912), No. 5, 

 pp. 151, 152). — A discussion of Whitman's work regulating sex in pigeons, as 

 reported by Riddle and of an article by Peck previously noted (E. S. R., 26, 

 p. 773). Concerning the latter the author says: "It fails to account for the 

 male that produces principally females, however mated; and the female that 

 produces principally males. The most conspicuous cases of excess of one sex 

 that I have known or heard of in poultry were cases of males that produced 

 a large excess of females, however mated." 



Are horns in sheep a sex-limited chsiracter? W. E. Castle (Science, n. ser., 

 35 (1912), No. 902, pp. 574, 575). — ^A criticism of the conclusions in the article 

 of Arkell and Davenport, noted previously (E. S. R., 26, p. 769). The author 

 considers that the assumption of an inhibiting factor is superfluous, as Bate- 

 son's hypothesis that the horn chaiacter is dominant in males and recessive in 

 females is adequate to explain the results obtained. 



A critical examination of recent studies on color inheritance in horses, 

 A. H. Sturtevant (Jour. Genetics, 2 (1912), No. 1, pp. 41-51). — A r^sum§ of 

 papers dealing with English Thoroughbreds, Shires, Scotch Clydesdales, French 

 Percherons, and the American Harness horse. The work is summarized as 

 follows : 



" It seems probable that chestnut always breeds true. Therefore the placing 

 of chestnut or yellow at the bottom of the scale probably represents the con- 

 dition of nearly all breeds of horses. Epistatic to it is black. Next comes, in 

 the breeds studied, bay or brown, epistatic to both the preceding. Gray is next 

 higher. Next is roan, which is probably always evident when present (unless 



