ANIMAL PRODUCTION. . 75 



cussion of points in which the author thinlvs it has deterioi'ated since then, 

 and suggestions for its improvement. Parts 2 and 3 treat respectively of 

 heredity and the practical part of horse breeding. 



State leg-islation regulating the standing of stallions and jacks for public 

 service, R. A. Cave (U. H. Dcpt. Agr., Bur. Anim-. Indus. Rpt. 1!)0S. i)i). 3:i5- 

 34'i)- — This article contains the text of the Wisconsin stallion law, notes on the 

 stallion laws of other States, and remarks on the beneficial results of this 

 legislation. 



Inheritance of characteristics in domestic fowl, C B. Davenport {(Jarnegie 

 Inst. Washington Pub. 121, pp. 100, pis. 12). — This work reports a series of 

 studies on the question of dominance and its varying potency in poultry and 

 contains a general discussion of the following topics: Relation of heredity and 

 ontogeny; dominance and recessiveness ; potency; reversion and the factor 

 hypothesis; the limits of selection; noninheritable characters; and the role of 

 hybridization in evolution. 



The potency of a character is defined as the capacity of its germinal deter- 

 miner to complete its entire ontogeny (E. S. R., 22, p. 671). 



A complete series of cases is reported which shows the different degrees of 

 potency of common characteristics found in poultry. The split or Y comb, 

 which results from mating a single comb with a V comb as seen in the Polish 

 race, is a heterozygous form due to imperfection of dominance of the median 

 element. It is a case where i-elative dominance varies from perfection to entire 

 absence and through all intermediate grades, the average condition being a 70 

 per cent dominance of the median element. When dominance is relatively weak 

 or of only intermediate grade the second generation of hybrids contains ex- 

 tracted pure dominance in the expected proportions of 1:2:1, but as the 

 potency of dominance increases in the parents the proportion of offspring with 

 the dominant (single comb) increases from the 25 per cent to 50 per cent. 

 This leads to the conclusion that on the one hand dominance varies quanti- 

 tatively and, on the other, that a degree of dominance is inheritable. The 

 index of heredity was found to be 0.301 it 0.002, which agrees closely with 

 Pearson's theoretical coefficient of correlation between offspring and parent. 



The studies on polydactylism revealed a similar variation of potency and 

 showed, in Houdans at least, an inheritance of potency. " There is some evi- 

 dence, derived from ' pure-bred ' Silkies, that differences in the degree of 

 development of the extra-toes are inherited. But the average condition of the 

 toes in the offspring of second or later generation hybrids can not be used as 

 evidence of inheritance of the degree of parental development of the toes, since 

 the.se are dependent on the same basal cause, namely, the hidden gametic con- 

 stitution of the parents. I>espite the obscuration of imperfect dominance, poly- 

 dactylism in poultry proves itself to be a unit-character that segregates." 



Syndactylism illustrates another step in the series of decreasing potency of 

 the dominant. On not one of the Fi generation was the dominant (syndactyl) 

 condition observed, and when these hybrids were mated together the dominant 

 character appeared in not 75 per cent but in from 10 per cent to none of the 

 offspring. " The striking fact, the one that assures us the segregation is 

 nevertheless occurring in this case too, is that some families (whose two parents 

 are extracted recessives) throw 100 per cent recessives. . . . Syndactylism is 

 a typical sport, that is, a rather large mutation having a teratological as- 

 pect. ... It is probable that syndactylism, under the conditions of the poul- 

 try yard, has little life and death significance, but is one of those neutral 

 characters whose existence Darwin clearly recognized." 



