ANIMAL PRODUCTION. 869 



Studies on chromosomes. — VII, A review of the chromosomes of Nezera; 

 with some more general considerations, E. I>. Wilson {Jour. Mori>h., 22 

 (Wll), ^'0. 1, PI). 11-110, 1)1. 1, Jigs. .9).— In the latter part of this paper the 

 author summarizes, under the following headings, the work on chromosomes 

 which he has reported at various times and places for the past 6 years : 

 (1) The idiochromosomes, (2) composition and origin of the X Y pair, (3) 

 modifications of the X element, (4) sex limited heredity, and (5) secondary 

 sexual characteristics. 



Though believing that in the chromosomes we have the mechanism which 

 may exphiin some of the phenomena of heredity, he does not think that they 

 are the exclusive factors of determination. Sex limited heredity is seen to run 

 parallel to the distribution of definite structural elements, and there is a. 

 remarkable consistencj^ of the chromosome relation in the species. Skepticism 

 regarding it is said to have no justification, though individual fluctuations do 

 occur. 



[The inheritance of complex growth forms, such as stature, and Mendel's 

 theory,] J. Brownlee {Proc. Roy. Soc. Edinh., 31 (1910-11), No. 2, pp. 251- 

 256). — The inheritance of complexes is illustrated by assuming a simple case 

 where two races mix in equal numbers and the property in question depends 

 upon two elements, and it is thereby shown that there is nothing necessarily 

 antagonistic between the evidence ad^anced by the biometricians and the 

 Mendelian theory. 



" If the inheritance of stature depends upon a Mendelian mechanism, then 

 the distribution of the population as regards height will be that which is 

 actually found, namely, a distribution closely represented by the normal curve. 

 There is nothing in the values of tbe coefficients of inheritance found by Sir 

 Francis Gallon and Professor Pearson which can not be explained on the basis 

 of Mendelian inheritance." 



The inheritance of the peculiar pigmentation of the Silky fowl, W. Bate- 

 sox and R. C. Punneti' {Jour. Genetics, 1 {1911), No. 3, irp. 185-203).— This is 

 a study of the inheritance of the black pigment which is generally distributed 

 among most of the mesodermal tissues of the body in Silky fowls. 



Offspring of a Silky hen crossed with a Brown Leghorn male which never 

 had this pigment possessed but little pigmentation, whereas those of the re- 

 ciprocal crosses were strongly pigmented. 



On breeding the Fi birds together there resulted chicks of various grades of 

 pigmentation, i-anging from the deepest pigment to none at all. The F2 genera- 

 tion, however, presented certain distinctions according as a pigmented or non- 

 pigmented Fi hen was used. When the Fi female was crossed with tbe Brown 

 Leghorn male none of the offspring was deeply pigmented, and this was true 

 for the pigmented Fi female as well as for the unpigmented. But when the Fi 

 male was crossed with a Bro^\Ti Leghorn female about 1 in 8 of the offspring 

 was deeply pigmented, and these were always females. Apparently there was 

 a pigmentation factor, an inhibition factor, and a sex factor. 



The Brown Leghorn male was homozygous for the inhibiting factor, and 

 the female is, according to the hypothesis of the authors, always heterozygous 

 for this factor. Because of certain exceptions to these results the authors are 

 inclined to think that upon occasion the repulsion between factors may be 

 imperfect, though it is not known whether this imperfection is sporadic or a 

 part of some orderly scheme. 



A Silky male was mated to a white Rosecomb bantam, and the results show 

 that although the strain of Brown Leghorns was homogeneous in resjject to 

 the factor modifying pigmentation, yet its behavior with regard to the Silky 

 pigmentations was not necessarily tyi5i<^al of breeds with unpigmented shanks. 



