ANIMAL PRODUCTION. 671 



" Oat feeds; because of the low feeding value of the extraneous oat hulls with 

 which they all are more or less laden. 



"Alfalfa meals; because the payment of a concentrate price for hay even 

 though it be ground is absurd." 



Experimental evidence on the effectiveness of selection, H. S. Jennings 

 (Amer. Nat., 4} (1910), No. 519, pp. 136-145). — A paper, read before the Amer- 

 ican Society of Naturalists December 29, 1909, which gives a discussion of the 

 significance of pure lines (E. S. R., 21. pp. 469, 771) in the evolution of types. 

 The author suggests that Johannsen's term " genotype " be substituted for 

 " pure line," and defines genotype as " a set of individuals which so long as 

 they are Interbred produce progeny that are characteristically uniform in their 

 hereditary features, not systematically splitting into diverse groups." It is 

 pointed out that Galton's law of ancestral inheritance does not hold in pure 

 lines, even in a statistical sense, and that investigators who have brought about 

 changes in type by selection have not worked with genotypes. 



" What the pure line work shows (agreeing in this with other lines of evi- 

 dence) is that the changes on which selection may act are few and far between, 

 instead of abundant; that they are found not oftener than in one individual in 

 ten thousand, instead of being exhibited on comi)aring any two specimens; that 

 a large share of the differences between individuals are not of significance for 

 selection or evolution — these being precisely the differences measured as a rule 

 by the biometrician's ' coefficient of variation.' . . . The work with genotypes 

 brings out as never before the minuteness of the hereditary differences that 

 separate the various lines. These differences are the smallest that can possibly 

 be detected by refined measurements taken in connection with statistical treat- 

 ment. . . . The genotypic work lends no support to the idea that evolution 

 occurs by large steps, for it reveals a continiious series of the minutest differ- 

 ences between great numbers of existing races. . . . 



"Altogether, I think we may say that the pure line or genotype concept pre- 

 sents an instrument of analysis which is worthy, on the basis of what it has 

 thus far done, of a thorough tryout for future work, and no one interested in 

 these questions can afford to neglect it." 



The imperfection of dominance and some of its consequences, C. B. Daven- 

 port (Aincr. Nat., ij {1910), No. 519, pp. 129-135).— X paper, read before the 

 American Society of Naturalists Dec-ember 29, 1909, in which the author cites 

 several examples of imperfect dominance, of which there are all degrees, and 

 explains them on the hypothesis that a determiner, though present, may fail to 

 complete its ontogeny, or, in other words, that the dominance is not reversed 

 but merely weakened. The determiner may be so weak that the character may 

 fail completely in a development of the heterozygote, and even in a homozygote 

 will give the impression of noninheritability. 



" By the aid of the facts of imperfection in dominance and the hypothesis of 

 varying potency of determiners the territory to which the jirinciple of the 

 segregation of determiners is applicable becomes. greatly extended." 



On a new method of determining' correlation between a measured charac- 

 ter A, and a character B, of which only the percentage of cases wherein B 

 exceeds (or falls short of) a g'iven intensity is recorded for each grade of A, 

 K. Peauson {Biometrika, 7 (1909), No. 1-2, pp. 96-105). — A new and rapid 

 method of determining correlation when one variable is given quantitatively 

 ;ind the other is divided into two classes only is presented. Hitherto such prob- 



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