Reports to the Evolution Committee of the Royal Society. 1-5.

Date:
1902-1910
Catalogue details

Licence: In copyright

Credit: Reports to the Evolution Committee of the Royal Society. 1-5. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    111/526 (page 107)
    Dominant First Crosses bred with Pure Fiecessive. 41. The four pullets used in Experiment 40 after their resting- season were for the remainder of 1901 put with a pure Leghorn cockerel Leg. 369 They gave 46 r.c. and 50 s.c, or almost equality, which the law demands. All chicks of course light in colour. This experiment was very kindly carried out for me by Mr. E. Assheton, Lecturer on Biology to Guy's Hospital. 42. A similar experiment was made with three dominant first crosses raised respectively in Experiments 5, 15, and 16. Put with a pure Leghorn (355 cJ), for the latter weeks of 1901 they gave— P.O. s.o. Light down. Dark down. 28 30 57 0 Here again the approach to equality is very close. There are of course no dark coloiu'ed chicks, as only one grandparent was coloui-ed. Nevertheless, that the peculiarity of the male if permanent is not of itself enough to explain the aberrations, is shown by a comparison of Experiments 37 with 38 and 39. In Experiment 37 the same male was used as in Experiment 39, the females being the same in Experi- ments 38 and 39. But while the feet are practically 3D : IE, in Ex- periments 37 and 38, they are 4-7 : 1 in Experiment 39. Conversely, AA'hile the combs are 3'3 :1 in Experiment 39, they are about 5:1 in the other two experiments. There is at present no obvious explana- tion of these results, and we can only accept the conclusion that not only clitFerent individuals similarly bred may give different propor- tions, but that these proportions may change also at different times p. 121). Totals of Mendelian First Crosses bred together. Experiments 34—39, added together, give the following totals. Though not strictly legitimate, such promiscuous addition is rendered less objectionable for the reason that in the case of each character which departs considerably from 3:1, there are grounds for regarding such a departure as an oscillation and not a departure peculiar to the character. Pea comb and single comb— P.e. S.c. Experiment 34 166 59 35 19 6 36 147 45