There are a few races of poultry that have two kinds of males, one with the feathering of the ordinary cock, the other with the feathering of the hen. The Hamburgs and the Campines are perhaps the best known races of this sort. Convention amongst breeders, in certain countries, has determined that the cock-feathered bird shall be the standard, and at other times and places that the hen-feathered males shall be the show birds. In one breed, at least, viz., the Sebright bantams, the hen-feathered

Darwin seems to have felt the necessity of giving some other explanation for the secondary sexual differences between the male and female than that such differences were only a by-product or concomitant of sex itself. His reason for searching further was probably a part of the general point of view he had reached in regard to the utility of special structures of animals, namely, that their presence finds its explanation on the basis of utility. Believing as he did that most of the adaptations of

The genetic and operative evidence shows that there has been included under the general term “secondary sexual characters” a complex of cases that are the outcome of diverse physiological processes. Sex-linked and sex-limited characters have often been confused; some characters depend on the gonad; some of these involve the ovary, others the testes. Still other characters fall under none of these groups, but are the direct product of the male or female genetic constitution. It is not surprising,

1. The two principal results obtained were: ( a ) that castration of hen-feathered Sebright males causes them to develop the full plumage characteristic of the cock-bird; ( b ) that complete hen-feathering is due to two dominant Mendelian genes. 2. A striking change takes place when the Sebright male is castrated ( plate 1 , figs. 3, 4; plate 3 , fig. 1). The new feathers on the upper surface of the head, neck, back, wings, rump, and tail-coverts assume a different color and distribution of thei

Alcock, A. , 1892. On the habits of Galasimus annulipes . An. Mag. Nat. Hist., VI. Ancel, P., et Bouin , 1906. Sur l’effet des injections d’extrait de glande interstitielle du testicule sur la croissance. Compt. Rend. Acad. Sc. Paris, CXLII. Arkell, T. R. , 1912. Some data on the inheritance of horns in sheep. N. H. Agr. Exp. Sta. Bull., 160. —— ——, 1912. The nature of the inheritance in sheep. Science, n. s., XXXV. —— ——, and C. B. Davenport , 1912. Horns in sheep as a typical sex-limited chara

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