Inheritance of Characteristics in Domestic Fowl - Charles Benedict Davenport

Table 26.—Progeny of tailless cock and tailed hens.

Serial No.	Pen No.	Father.	Mother.		Offspring.
			No.	Races.	Condition of uropygium.			Per cent rumpless.
			No.	Races.	Present.	Small.	Absent.	Per cent rumpless.
1	525	117	114	Nankin.	3	...	0	0
2	526	117	20a	Frizzle.	8	...	0	0
3	532	117	...	Bl. Coch.	14	...	0	0
4	532a	117	127	Wh. Legh.	19	...	0	0
4a	653	117	508	Bl. Coch. × Wh. Legh.	8	3	0	0
				Totals	52	3	0	0

In 25 cases of the 52 an oil-gland was looked for and, in every case, it was found to be missing.

Table 26, the conclusions from which were drawn in my 1906 report, seemed to indicate the dominance of tail over its absence. On this hypothesis I suspected that if No. 117 were bred to his (tailed) offspring about 50 per cent of the progeny would be tailless, and if the tailed hybrids of the F₁ were bred together about 25 per cent of their progeny should be tailless. The actual result of such matings is shown in table 27.

Table 27.—Heterozygotes mated with father.

Serial No.	Pen No.	Tailless cock × heterozygotes.		Offspring.
		Father.		Mother.		Condition of uropygium.
		No.	From pen No.	No.	From pen No.	Present.	Small.	Absent.
5	653	117	Original.	577	532	6	1	0
6	653	117	Do.	587	532	8	2	0
7	653	117	Do.	635	532	7	0	0
8	653	117	Do.	691	532	5	2	0
9	653	117	Do.	652	532	15	0	0
10	653	117	Do.	691	532	5	2	0
11	653	117	Do.	705	532	9	2	0
12	653	117	Do.	713	532	7	2	0
13	653	117	Do.	760	532	13	2	0
14	653	117	Do.	799	532	7	0	0
		Total				82	13	0

Table 28.—Heterozygotes mated inter se.

Serial No.	Pen No.	Father.		Mother.		Condition of uropygium in offspring.
		Father.		Mother.		Frequency.			Percentage.
		No.	From pen No.	No.	From pen No.	Present.	Small.	Absent.	Present.	Small.	Absent.
15	661	466	526	401a	526	5	0	0	100	0	0
16	661	466	526	635	532	5	0	0	100	0	0
17	661	466	526	691	532	4	0	0	100	0	0
18	661	466	526	799	532	4	1	0	80	20	0
19	649	516	532a	521	532a	17	4	0	81	19	0
20	649	516	532a	565	532a	24	7	0	77	23	0
21	649	516	532a	665	532a	11	4	0	73	27	0
22	649	516	532a	692	532a	18	1	0	95	5	0
23	652	343	525	344	525	8	2	0	80	20	0
24	661	428	526	635	532	4	0	0	100	0	0
25	661	428	526	691	532	3	0	0	100	0	0
26	661	428	526	799	532	5	0	0	100	0	0
Total						108	19	0	85	15	0

The results given in tables 27 and 28 are remarkable. Neither in the DR × R nor the DR × DR crosses did the tail fail to develop. The tailless condition, that I had strongly suspected of being recessive and expected in 25 per cent to 50 per cent of the offspring, never once appeared. The only point of variation in the uropygium of the chicks derived from the back cross or from F₁'s bred inter se was that in some the uropygium seemed distinctly smaller than in the others. This small uropygium was as a matter of fact recorded chiefly in chicks that failed to hatch, but it was occasionally noticed in older birds, being then usually associated with a slight convexity of the back. In some of the families the uropygium is recorded as small in suspiciously close to 25 per cent of the offspring. There is little doubt in my mind that this small uropygium represents in some way the "absence" of tail that was expected.

The next step was to cross the other rumpless bantam (No. 116), to see if he behaved like his father. Accordingly, in pen 653, I replaced the cock No. 117 by 116, the hens remaining the same, and got the result shown in table 29.