GENERAL, TOPICS IN INHERITANCE. 93 



COMPARISON OF RECIPROCAL CROSSES. 



There is a notion among breeders of poultry that the father and the mother 

 contribute different qualities to the offspring ; and if the cytoplasm carries 

 any hereditary tendencies this result is to be expected, for the female trans- 

 mits more cytoplasm than the male. Certainly the hybrid between a large 

 hen and a bantam cock starts life on a very different plane of size from the 

 hybrid between a bantam hen and a large cock. A writer in Wright's 

 Poultry Book (1902) says in respect to breeding Houdans that the male bird 

 is more responsible for the outside qualities color, size of crest, beard, tail 

 carriage, color of legs, and so on. The hen determines laying qualities and 

 general size. 



I have made only one extensive experiment on this matter. I crossed a 

 single-comb White Leghorn bantam and a Dark Brahma both ways. The 

 offspring of the Dark Brahma hen (weight, 1,300 grams) are a little heavier 

 than those of the White Leghorn bantam hen (weight, 700 grams). Two 

 males descended from the one and the other mother, respectively, weighed 

 at 3^2 months 720 and 550 grams. The average of three pullets from the 

 Dark Brahma at 3 months 22 days is 655 grams ; of three pullets from the 

 White Leghorn at 3 months 23 days is 626 grams. The proportional differ- 

 ence in the weight of the young of about 3 to 4 months is less than that of 

 their parents, but is in the same sense. 



The booting of the offspring of the White Leghorn hen is much reduced 

 as compared with the booting of the offspring of the Dark Brahma hen, the 

 father in the first cross not differing from the mother in the second cross 

 in its heavy booting. In plumage color the 19 offspring of the White Leg- 

 horn female were all white except four. Of the 19 offspring of the Dark 

 Brahma female, only six were white, the others resembling the Dark Brahma. 

 Thus we see that in these three characters of weight, booting, and plumage 

 color the offspring tended to ' ' take after ' ' the mother. 



INHERITANCE OP SEXUALLY DIMORPHIC CHARACTERISTICS AND SEXUAL 

 DIMORPHISM IN THE HYBRIDS. 



Most species of vertebrates exhibit certain characteristics peculiar to one or 

 the other sex, and it is well known that, for example, a female peculiarity 

 can be transmitted through a son to a granddaughter. Thus the good 

 milking quality of a cow is transmitted through her son to his daughters. 

 Whenever femaleness crops out in the history of the germ plasm the good 

 milking quality, or whatever other quality it may be, also appears. The 

 inheritance of dimorphic characters is most strikingly seen in hybridization. 

 Thus I crossed a male Tosa fowl (which has self-colored feathers) with a 

 white Cochin.* The male hybrids are barred with white, but the female 

 hybrids closely resemble in color the female Tosa fowl in having white 



* See Series IX. 



