BOOTING.
The method of inheritance of the feathering on the feet of some
poultry has already been made the subject of much study. Hurst
(1905, p. 152) crossed booted and non-booted birds and bred the
hybrids together. He concluded that "the Mendelian principles are at
work in these aberrant phenomena, but are masked by something not
yet perceived." My own conclusion (1906, p. 72) was: "Booting is
dominant, but usually imperfectly so." A more extended study has been
desirable.
Booting is variable in amount. To indicate its degree I have had
recourse to an artificial scale. I recognize 11 grades, running from
0 to 10. The grade 0 implies no feathers whatsoever. Grade 10 implies
heavy booting extending over the front half of the shank. Grade 5
implies an extent of only half of the maximum, _i. e._, the outer
front quarter of the shank. Intermediate grades indicate intermediate
extension of the feathered area.
A. TYPES OF BOOTING.
The races of booted poultry used have been as follows: First, bantam
Cochins of two varieties; second, a bantam Dark Brahma; and third,
the Silkie. In my representatives of the first two groups, but
particularly in the Dark Brahma, the amount of booting is variable.
In one type the outer third of the shank in the newly hatched
chick is covered by strong, heavy, specialized feathers, directed
outward, while the middle and inner thirds are covered by smaller,
finer, imbricating feathers sparsely placed and resembling reduced
contour-feathers. In most individuals the transition from the one
kind to the other is gradual, while in others it is sharp, and in a
few the outer third only of the shank is feathered. In the Silkies,
which the standard poultry books describe as being more sparsely
feathered on the shank,[8] the outer zone of feathers is the only one
developed; and, occasionally, as table 31 shows, even these feathers
may be lacking. We have thus two types to distinguish--the extended
(Cochin, Brahma) type and the restricted type.
[8] Thus Wright (1902) says the shanks of the Silkies
(in England) are "slightly feathered," and Baldanus (1896) says
that (in Germany) they are feathered on the _outer half_.
B. NORMAL VARIABILITY.
To appreciate the results of hybridizing we must first examine the
variability of pure-blooded races. This is done in table 31.
TABLE 31.--_Distribution of boot-grades in the offspring of
Cochin, Dark Brahma, and Silkie parents._
+---------------------------------------------------------------------------------------------+
| A. OFFSPRING OF COCHIN PARENTS. |
+----+------------+------------+--------------------------------------------------------------+
| | Mother. | Father. | Grades of boot in offspring. |
|Pen |-----+------+------+-----+----+---+----+----+----+----+----+----+----+----+----+--------+
|No. | | Boot-| |Boot-| | | | | | | | | | | | |
| | No.| grade| No. |grade| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Average.|
+----+-----+------+------+-----+----+---+----+----+----+----+----+----+----+----+----+--------+
|848 | 2297| 10 | 545 | 10 |.. | ..| .. | 1 | .. | .. | 1 | .. | .. | 1 | 18 | 9.43 |
|776 | 2574| 10 | 2732 | 8 |.. | ..| .. | .. | .. | .. | .. | .. | 3 | 2 | 6 | 9.27 |
|848 | 2300| 8 | 545 | 10 |.. | ..| .. | .. | .. | .. | .. | .. | 1 | 2 | 5 | 9.25 |
|776 | 2570| 6 | 2732 | 8 |.. | ..| .. | .. | .. | .. | 1 | 1 | .. | 11 | 1 | 8.71 |
|848 | 2075| 9 | 545 | 10 |.. | ..| .. | .. | .. | 1 | 1 | .. | .. | .. | 4 | 8.50 |
|776 | 2072| 6 | 2732 | 8 |.. | ..| .. | .. | .. | .. | 1 | .. | 4 | 2 | 2 | 8.44 |
|758 | 130| 6 | 545 | 10 |.. | ..| .. | .. | .. | 1 | 1 | 1 | 3 | 9 | .. | 8.20 |
|776 | 2073| 6 | 2732 | 8 |.. | ..| .. | .. | 1 | 2 | .. | 2 | 2 | 10 | 1 | 8.00 |
|776 | 2300| 6 | 2732 | 8 |.. | ..| .. | .. | 1 | .. | 1 | 3 | 6 | 5 | 2 | 8.00 |
|758 | 131| 10 | 545 | 10 |.. | ..| .. | .. | .. | 1 | .. | 4 | 6 | 1 | 1 | 7.96 |
|776 | 2297| 6 | 2732 | 8 |.. | ..| .. | 1 | .. | 1 | .. | 3 | 6 | 6 | 2 | 7.95 |
|776 | 1132| 3 | 2732 | 8 |.. | ..| .. | 1 | 1 | 1 | 1 | 3 | 6 | 8 | .. | 7.57 |
|776 | 2937| 7 | 2732 | 8 |.. | ..| .. | .. | .. | .. | 1 | 3 | 3 | 1 | .. | 7.50 |
|776 | 2299| 7 | 2732 | 8 |.. | ..| 1 | .. | .. | 1 | 1 | 4 | 7 | 3 | 1 | 7.44 |
| +----|---+----+----+----+----+----+----+----+----+----+--------+
| Totals (199) |.. | ..| 1 | 3 | 3 | 8 | 9 | 24 | 47 | 61 | 43 | 8.24 |
+------------------------------+----+---+----+----+----+----+----+----+----+----+----+--------+
| B. OFFSPRING OF DARK BRAHMA PARENTS. |
| [All individuals have sprung from No. 121 ♀ (boot of grade 9) and No. 122 ♂ |
| (boot of grade 6).] |
+---------------------------------------------------------------------------------------------+
|816 | 2030| 6 | 122 | 6 | .. | ..| .. | .. | .. | .. | .. | .. | .. | 1 | 3 | 9.8 |
|703 | 2030| 6 | 122 | 6 | .. | ..| .. | .. | .. | .. | 4 | 2 | 0 | 3 | 6 | 8.3 |
|816 | 121| 6 | 122 | 6 | .. | ..| .. | .. | .. | .1 | 3 | 1 | 2 | 4 | 5 | 8.3 |
|816 | 5979| 6 | 122 | 6 | .. | ..| .. | .. | .. | .. | 1 | 0 | 2 | .. | .. | 7.3 |
|816 | 2353| 5 | 122 | 6 | .. | ..| .. | .. |[A]1| 1 | 1 | 0 | 1 | 0 | 2 | 7.1 |
|816 | 5835| 5 | 122 | 6 | .. | ..| .. |[A]1| 0 | 1 | 2 | .. | .. | 1 | 3 | 6.5 |
|816 | 5840| 5 | 122 | 6 | .. | ..| .. |[A]1| .. | .. | 1 | .. | .. | .. | 1 | 6.3 |
|703 | 2353| 5 | 122 | 6 | .. | ..| .. | .. | 1 | 1 | 3 | .. | 1 | .. | .. | 5.8 |
| +----+---+----+----+----+----+----+----+----+----+----+--------+
| Totals (61) | .. | ..| .. | 2 | 2 | 4 | 15 | 3 | 6 | 9 | 20 | 7.62 |
+------------------------------+----+---+----+----+----+----+----+----+----+----+----+--------+
| C. OFFSPRING OF SILKIE PARENTS. |
+----+-----+------+------+-----+----+---+----+----+----+----+----+----+----+----+----+--------+
|734 | 468| 4 | 774 | 3 | .. | ..| 1 | 2 | .. | .. | 1 | 1 | .. | .. | .. | 4.20 |
|734 | 1002| 3 | 774 | 3 | .. | ..| 1 | 4 | .. | 1 | 3 | .. | .. | .. | .. | 4.11 |
|734 | 841| (?)| 774 | 3 | .. | ..| .. | .. | 2 | .. | .. | .. | .. | .. | .. | 4.00 |
|815 | 7434| 7 | 774 | 3 | .. | ..| .. | .. | 2 | .. | .. | .. | .. | .. | .. | 4.00 |
|734 | 773| 1 | 774 | 3 | .. | ..| .. | 2 | 2 | .. | .. | .. | .. | .. | .. | 3.50 |
|734 | 680| 1 | 774 | 3 | .. | ..| .. | 2 | .. | .. | .. | .. | .. | .. | .. | 3.00 |
|734 | 405A| 1 | 774 | 3 | .. | ..| 1 | 3 | 1 | .. | .. | .. | .. | .. | .. | 3.00 |
|815 | 499| 2 | 774 | 3 | 1 | 1| 3 | .. | .. | 2 | .. | 1 | .. | .. | .. | 3.00 |
|734 | 499| 2 | 774 | 3 | 1 | 1| 5 | 2 | 2 | 1 | .. | .. | .. | .. | .. | 2.50 |
|734 | 500| 1 | 774 | 3 | 2 | 1| 2 | 3 | .. | .. | .. | .. | .. | .. | .. | 1.75 |
|815 | 773| 1 | 774 | 3 | 4 | 1| 3 | .. | .. | .. | .. | .. | .. | .. | .. | 1.25 |
|815 | 500| 1 | 774 | 3 | 1 | 1| .. | .. | .. | .. | .. | .. | .. | .. | .. | 0.50 |
|815 | 496| 3 | 774 | 3 | 1 | ..| .. | .. | .. | .. | .. | .. | .. | .. | .. | 0.00 |
| +----+---+----+----+----+----+----+----+----+----+----+--------+
| Totals(68) | 10 | 5| 16 | 18 | 9 | 4 | 4 | 2 | .. | .. | .. | 2.72 |
+------------------------------+----+---+----+----+----+----+----+----+----+----+----+--------+
| SUMMARY. |
+------------------------------+--------------------------------------------------------------+
| | Grades of boot in offspring, reduced to percentages. |
| Races. +----+---+----+----+----+----+----+----+----+----+----+--------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Average.|
+------------------------------+----+---+----+----+----+----+----+----+----+----+----+--------+
|Cochins | .. | ..| 0.5| 1.5| 1.5| 4.0| 4.5|12.1|23.6|30.7|21.6| 8.24 |
|Dark Brahmas | .. | ..| .. | 3.3| 3.3| 6.6|24.6| 4.9| 9.8|14.8|32.8| 7.62 |
|Silkie |14.8|7.4|23.5|26.5|13.2| 5.9| 5.9| 2.9| .. | .. | .. | 2.72 |
+------------------------------+----+---+----+----+----+----+----+----+----+----+----+--------+
[A] Determination made on embryo chicks.
An inspection of table 31 shows that, in respect to booting, the
Cochins and Dark Brahmas are clearly closely related to each other.
Owing to smaller numbers and to other circumstances that will be
discussed later, the results are less regular in the Dark Brahma
offspring, but in both the range is from 2 or 3 upward to 10, with
a great preponderance in grades above 5. In the Silkies, on the
other hand, the greatest frequency is found in grades below 5. This
difference is correlated with a difference of the parents, for the
commonest grades of the parents of the Cochins are between 6 and 10,
of the Dark Brahmas between 5 and 9, and of the Silkies between 1 and
3. These results suggest that the Silkie is typically heterozygous in
boot, producing 25 per cent recessives (boot of grade 4-7) and 75 per
cent dominant (0, 1) and heterozygous (2, 3). We shall see that this
hypothesis receives support from all Silkie matings.
Inside of any part of this table it appears that, on the whole, as
the average grade of the boot in the progeny diminishes that of
the parentage diminishes, although the correlation is by no means
perfect. Thus the average of the parental grades in the first part of
table 31, A (which is arranged in descending order of the averages
of the offspring) is 8.5; in the lower half, 7.4. The average of
parental grades in the upper half of table 31, B is 6.4; in the lower
half 5.5. In table 31, C the grades are 2.9 and 2.3, respectively.
This correlation indicates, without exactly measuring, heredity in
grade of booting.
Table 32 shows the results of crosses between Cochins (high grade of
boot) and Silkies (low grade).
TABLE 32.--_Distribution of boot-grades between a high and low
grade of boot in parents._
+---------------------------------------------------------------------------------------------------+
| HIGH AND LOW GRADE OF BOOT IN PARENTS. |
+---+-----------------------------+-----------------------+-----------------------------------------+
| | Mother. | Father. | Grade of boot in offspring. |
|Pen|-----+----+-------------+----+-----+----+-------+----+--+--+--+--+--+--+--+--+--+--+--+--------+
|No.| | | | | | | | | | | | | | | | | | | | |
| | No. |Gen.| Races. |Gra.| No. |Gen.| Race. |Gra.| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10|Average.|
+---+-----+----+-------------+----+-----+----+-------+----+--+--+--+--+--+--+--+--+--+--+--+--------+
|851| 5567| P | Bl. × Bf. C.| 9 | 7526| P | Silkie| 3 |..|..|..|..| 2|..|..|..| 3| 3| 5| 8.15 |
|851| 3410| P | Do. | 9 | 7526| P | Do. | 3 |..|..|..|..|..| 4| 3| 2| 1| 6| 1| 7.29 |
|851| 6956| P | Do. | 8 | 7526| P | Do. | 3 |..|..|..|..| 3| 3|..| 2| 2|..| 5| 7.13 |
|851| 2073| P | Do. | 7 | 7526| P | Do. | 3 |..| 1|..| 1| 1|..| 1| 1| 1| 3| 2| 6.91 |
|851| 2299| P | Do. | 7 | 7526| P | Do. | 3 |..|..|..|..| 2| 2| 1| 1|..|..| 3| 6.78 |
|851| 840| P | Bf. C. | 10 | 7526| P | Do. | 3 |..|..|..|..| 1|..| 1|..|..| 1|..| 6.33 |
|851| 1002| P | Do. | 8 | 7526| P | Do. | 3 |..|..|..| 3| 1| 2| 1| 2| 4| 1| 1| 6.27 |
|815| 131| P | Bk. C. | 10 | 774| P | Do. | 4 |..|..|..| 3| 1| 1| 2| 2| 1| 1| 2| 6.23 |
|851| 841| P | Bf. C. | 10 | 7526| P | Do. | 3 |..|..|..|..| 1|..| 1|..| 1|..|..| 6.00 |
|851| 838| P | Do. | 8 | 7526| P | Do. | 3 |..|..|..| 4| 2| 4| 3|..|..| 2| 2| 5.65 |
| |--+--+--+--+--+--+--+--+--+--+--+--------+
| Totals (116) | 0| 1| 0|11|14|16|13|10|13|17|21| 6.77 |
+---------------------------------------------------------+--+--+--+--+--+--+--+--+--+--+--+--------+
So far as the average grade of boot in offspring goes, this table
stands between that of the Cochins (table 31, A) and that of the
Silkies (table 31, C). But what is especially striking is the
apparent dimorphism revealed in the line of totals. There is one
(empirical) mode at 10, corresponding with that of the Cochins, and
a second clear mode at 5, corresponding to that of the Silkies. If
we assume the Cochin to be homozygous in boot (RR) and the Silkie
to be heterozygous in boot, then we can interpret the high mode as
extracted recessives, the median mode as heterozygotes.
C. RESULTS OF HYBRIDIZATION.
We have next to consider the nature of the inheritance when one
parent belongs to an unbooted race, the other to a booted one (table
33).
TABLE 33.--_Distribution of boot-grades in the F1 generation of booted × non-booted parents._
+------------------------------------------------------------------------------------------------------------------+
| A. COCHIN CROSSES. |
+---+----------------------------+----------------------------+----------------------------------------------------+
|Pen| Mother. | Father. | Grade of boot in offspring. |
|No.|----+----+-------------+----+-----+----+------------+----+---+---+---+---+---+---+---+---+---+---+---+--------+
| | No.|Gen.| Races. |Gra.| No. |Gen.| Races. |Gra.| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 10|Average.|
+---+----+----+-------------+----+-----+----+------------+----+---+---+---+---+---+---+---+---+---+---+---+--------+
|773|1334| P | W. Legh. | 0 | 836| P | Bl. Coch. | 10 | ..| ..| ..| 3| 1| 1| 1| 1| ..| 2| ..| 5.44 |
|773| 193| P | Do. | 0 | 836| P | Do. | 10 | ..| 1| 2| 6| 8| 7| 4| 2| ..| ..| ..| 4.27 |
|773|1366| P | Do. | 0 | 836| P | Do. | 10 | ..| ..| ..| 2| 5| 2| 1| ..| ..| ..| ..| 4.20 |
|773| 127| P | Do. | 0 | 836| P | Do. | 10 | ..| ..| 3| 10| 9| 12| 4| ..| ..| ..| ..| 4.11 |
|773| 692| P | W. Legh. (R)| 0 | 836| P | Do. | 10 | ..| ..| ..| 10| 3| 2| ..| ..| ..| ..| ..| 3.47 |
|774|2075| P | Coch. | 8 | 1431| P |W. Legh. (R)| 0 | 6| 1| 1| ..| 1| ..| ..| ..| ..| ..| ..| 0.78 |
| +---+---+---+---+---+---+---+---+---+---+---+--------+
| Totals (111) | 6| 2| 6| 31| 27| 24| 10| 3| 0| 2| 0| 3.91 |
+-------------------------------------------------------------+---+---+---+---+---+---+---+---+---+---+---+--------+
| B. DARK BRAHMA CROSSES. |
+---+----+----+-------------+----+-----+----+------------+----+---+---+---+---+---+---+---+---+---+---+---+--------+
|727| Y| P | D. Br. | 10 | 381| P | Houd. | 0 | ..| ..| ..| ..| 2| 3| 2| 1| 2| ..| ..| 5.80 |
|727| 121| P | Do. | 10 | 381| P | Do. | 0 | 1| ..| ..| 1| 1| 5| 4| ..| ..| ..| ..| 4.67 |
|823|2030| P | Do. | 7 | 3858| P | M × P | 0 | ..| ..| 5| 16| 15| 4| 1| 2| ..| ..| ..| 3.67 |
|823| Y| P | Do. | 8 | 3858| P | Do. | 0 | ..| ..| 1| 7| 6| 2| ..| ..| ..| ..| ..| 3.56 |
|838|3814| P | W. Legh. | 0 | 122| P | D. Br. | 6 | ..| 2| 2| 6| 6| 1| 1| ..| ..| ..| ..| 3.28 |
|838| 202| P | Min. | 0 | 122| P | Do. | 6 | ..| ..| 2| 5| 3| ..| ..| ..| ..| ..| ..| 3.10 |
|838| 71| P | W. Legh. | 0 | 122| P | Do. | 6 | ..| ..| ..| 1| ..| ..| ..| ..| ..| ..| ..| 3.00 |
|838|3832| P | Do. | 0 | 122| P | Do. | 6 | 1| 1| ..| 1| 1| 2| ..| ..| ..| ..| ..| 3.00 |
|838| 10| P | Do. | 0 | 122| P | Do. | 6 | ..| 1| ..| 3| 1| ..| ..| ..| ..| ..| ..| 2.80 |
|816| 121| P | D. Br. | 9 | 4912| P | M × P | 0 | ..| ..| 8| 4| 1| 1| ..| ..| ..| ..| ..| 2.64 |
|816|5838| P | Do. | 9 | 4912| P | Do. | 0 | ..| ..| 5| 5| 1| ..| ..| ..| ..| ..| ..| 2.64 |
|838|5418| P | W. L., Min. | 0 | 122| P | D. Br. | 6 | 1| 1| 3| 3| 1| 1| ..| ..| ..| ..| ..| 2.50 |
|816|5979| P | D. Br. | 6 | 4912| P | M × P | 0 | 4| 3| 4| 7| 4| 1| 1| ..| ..| ..| ..| 2.46 |
|816|2353| P | Do. | 5 | 4912| P | Do. | 0 | ..| 2| 2| 4| 1| ..| ..| ..| ..| ..| ..| 2.44 |
|816|5977| P | Do. | 4 | 4912| P | Do. | 0 | ..| 3| 2| 1| ..| 1| ..| ..| ..| ..| ..| 2.14 |
|816|5835| P | Do. | 5 | 4912| P | Do. | 0 | 3| 5| 5| 8| 3| ..| ..| ..| ..| ..| ..| 2.12 |
|816|5840| P | Do. | 5 | 4912| P | Do. | 0 | 5| 1| 3| 4| 1| ..| ..| ..| ..| ..| ..| 1.64 |
|823|6626| P | Do. | 2 | 3858| P | Do. | 0 | 1| 10| 2| 2| ..| ..| ..| ..| ..| ..| ..| 1.33 |
|816|5980| P | Do. | 5 | 4912| P | Do. | 0 | 5| 8| 1| 5| ..| ..| ..| ..| ..| ..| ..| 1.32 |
| +---+---+---+---+---+---+---+---+---+---+---+--------+
| Totals (268) | 21| 37| 45| 83| 47| 21| 9| 3| 2| 0| 0| 2.84 |
+-------------------------------------------------------------+---+---+---+---+---+---+---+---+---+---+---+--------+
| C. SILKIE CROSSES. |
+---+----+----+-------------+----+-----+----+------------+----+---+---+---+---+---+---+---+---+---+---+---+--------+
|774| 777| P | Silkie. | 8 | 1176| P | W. Legh. | 0 | 3| ..| 1| 1| 1| ..| ..| ..| ..| ..| ..| 1.50 |
|744| 681| P | Do. | 5 | 1176| P | Do. | 0 | 11| 2| 1| 1| 1| 1| ..| ..| ..| ..| ..| 0.94 |
|744| 469| P | Do. | 1 | 1176| P | Do. | 0 | 11| 3| ..| ..| ..| ..| ..| ..| ..| ..| ..| 0.21 |
| +---+---+---+---+---+---+---+---+---+---+---+--------
| Totals (37) | 25| 5| 2| 2| 2| 1| 0| 0| 0| 0| 0| 0.76 |
+-------------------------------------------------------------+---+---+---+---+---+---+---+---+---+---+---+--------+
| SUMMARY. |
+---------------------------------------+---------------------------------------------------------------------------
| | Grades of boot in offspring, reduced to percentages. |
| Crosses. +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Average.|
+---------------------------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--------+
|Cochin | 5.4| 1.8| 5.4| 28.0| 24.3| 21.6| 9.0| 2.7| 0.0| 1.8| ..| 3.91 |
|Brahma | 7.8| 13.8| 16.8| 31.0| 17.5| 7.8| 3.4| 1.1| 0.7| ..| ..| 2.84 |
|Silkie | 67.6| 13.5| 5.4| 5.4| 5.4| 2.7| ..| ..| ..| ..| ..| 0.76 |
+---------------------------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--------+
An inspection of Table 33, which gives the distribution of grades of
boot in the offspring constituting the first hybrid generation, might
well lead to the conclusion that inheritance is here of a blending
nature, or that, if either condition is dominant, it is the booted
one, as suggested in my report of 1906. On this hypothesis the
offspring with no boot illustrate imperfection of dominance, and one
would say that, in booting, dominance is very imperfect.
However plausible such an interpretation might appear when based
on the first hybrid generation alone, it becomes untenable when
subsequent generations are taken into account, as we shall see
later. The hypothesis breaks down completely in the second hybrid
generation and we are forced to the opposite hypothesis, namely, that
the clean-shanked condition is dominant. Such an hypothesis would
seem, at first, to contravene the principle enunciated in my report
of 1906 that the more progressive condition is dominant over the
less progressive condition, or absence. But such is not necessarily
the fact. We have no right to assume that presence of boot is the
new character. The rest of the body of poultry (save the head) is
covered with feathers. If the foot is not it must be because there
is something in the skin of the foot that inhibits the development
of feathers there. And this inhibiting factor is dominant over its
absence.
Table 33 shows that the Silkie crosses yield an exceptionally high
per cent of the dominant clear-footed condition. This is additional
evidence that the Silkies are DR, and so this cross produces 50
per cent of pure extracted dominants in addition to 50 per cent of
heterozygotes in booting.
To get further light on the nature of inheritance of booting we pass
to the examination of the second hybrid generation (table 34).
In the case of Silkies, which throw 67.6 per cent clean-shanked
progeny in F1, we find in F2 only about 60 per cent clean-shanked.
This diminution is, of course, due to the extraction of some pure
booted recessives, which draw from the proportion of clean shanks.
In the case of the Cochins and Dark Brahmas, expectation, with
perfect dominance, is that 75 per cent of the offspring shall
be clean-shanked. Since dominance is imperfect (as shown by the
occurrence of many booted birds in F1) we should look for an actual
failure to reach so large a proportion, but we are hardly prepared
for the result that in most of the F2 crosses of Cochins and Brahmas
less than 25 per cent of the offspring are clean-shanked. In 4 pens
the average is only 10 to 12 per cent, and in one only 2 per cent
of the offspring fail to develop feathers on the feet. What shall
we say of such a case as the last? The history of the father (No.
666) is absolutely certain; his mother was No. 121, the original
Dark Brahma female, with a boot of grade 9 and a record in her
immediate progeny that indicates perfect purity of booting in her
germ-cells. His father was a White Leghorn with clean shanks and
without a suspicion of having such antipodal blood as the Asiatic
in his ancestry. No. 666 is certainly heterozygous in boot, if
boot is a single unit. The hens with which No. 666 were mated were
clearly heterozygous, as is known not only from their ancestry, but
also from their behavior when mated with another cock, No. 254, in
which case they threw 12 per cent non-booted offspring. If now both
parents are heterozygous they must produce 25 per cent recessives.
This is the fact that forces us to conclude that clean shank is not
recessive, but dominant and due to an inhibitor that frequently
_fails to dominate_. In table 31 the two recessive varieties, mated
_inter se_, produce no featherless shanks; the feathers grow freely
as they do over the rest of the body. Some of the Silkies of table
31, however, are really heterozygous, with the dominant inhibitor not
showing; consequently they throw a large proportion of non-booted
offspring. In F1, as table 33 shows, the heterozygous offspring
have a reduced boot and perfect dominance--complete inhibition of
boot--in from 6 to 68 per cent. Dominance is most complete in the
Silkies, where, the feathering being feeble, the inhibitor has, as
it were, less to do in overcoming it. In F2 the expected 75 per cent
dominant is approached in the case of the Silkies (62 per cent and
59 per cent, respectively), but inhibition is very imperfect in the
Cochin and Brahma crosses, being reduced to between 25 and 2 per
cent. More proof that boot is due to the absence of a factor rather
than to its presence is found in this generation. If absence of boot
is recessive, then, combined with imperfection of dominance, _at
least_ 25 per cent of the offspring should be recessive and probably
a much larger proportion. The results in table 34 are absolutely
incompatible with this hypothesis, since, in one case, there are only
2 per cent that can not develop boot. Two extracted clean-footed
birds sometimes throw boot and sometimes not, and this result is to
be expected on the hypothesis that clean-footedness is dominant, but
two heavily booted birds can not transmit the boot inhibitor.
TABLE 34.--_Distribution of boot-grade in the F2 generation of
booted × non-booted poultry._
+------------------------------------------------------------------------------------------------------------------+
| COCHIN CROSSES. |
+---+---------------------------------------+-------------------------------------+--------------------------------+
| | Mother. | Father. | Offspring. |
+---+---+-----+-----------------------------+---+----+---------------------+------+--------+-------+-------+-------+
|Pen|No.| Gen.| Races. | Grade.|No.|Gen.| Races. |Grade.| Boot | Boot | Boot | P. ct.|
|No.| | | | | | | | |present.|slight.|absent.|absent.|
+---+---+-----+---------------------+-------+---+----+-----+---------------+------+--------+-------+-------+-------+
|650|170| F1 |Bl. Coch. × Wh. Legh.| Pr. |265| F1 |Bl. Coch. × Wh. Legh.| Pr. | 19 | 2 | 2 | 8.7 |
|650|263| F1 | Do. | Pr. |265| F1 | Do. | Pr. | 36 | 2 | 2 | 5.0 |
|650|278| F1 | Do. | Pr. |265| F1 | Do. | Pr. | 26 | 4 | 4 | 11.8 |
|650|361| F1 | Do. | Pr. |265| F1 | Do. | Pr. | 24 | 2 | 9 | 25.7 |
|650|364| F1 | Do. | Pr. |265| F1 | Do. | Pr. | 39 | 5 | 3 | 6.4 |
| | | | +--------+-------+-------+-------+
| | | | Totals (179) | 144 | 15 | 20 | 11.1 |
| | | | | | | | |
| | | | |========|=======|=======|=======|
|654|602| F1 |Wh. Legh. × Bf. Coch.| Pr. |704| F1 |Wh. Legh. × Bf. Coch.| Pr. | 11 | 4 | 5 | 25.0 |
|654|828| F1 | Do. | Pr. |704| F1 | Do. | Pr. | 7 | 11 | 0 | 0.0 |
|654|640| F1 | Do. | Pr. |704| F1 | Do. | Pr. | 13 | 2 | 3 | 16.7 |
|654|696| F1 | Do. | Pr. |704| F1 | Do. | Pr. | 8 | 5 | 8 | 38.1 |
|654|767| F1 | Do. | Pr. |704| F1 | Do. | Pr. | 3 | 1 | 3 | 42.9 |
|654|697| F1 | Do. | Pr. |704| F1 | Do. | Pr. | 4 | 3 | 6 | 46.2 |
| | | | +--------+-------+-------+-------+
| | | | Totals (97) | 46 | 26 | 25 | 25.8 |
+---+---+-----+-------------------------------------------------------------------+--------+-------+-------+-------+
TABLE 34.--_Distribution of boot-grade in the F2 generation of
booted × non-booted poultry_--Continued.
+-------------------------------------------------------------------------------------------------------------------+
| DARK BRAHMA CROSSES. |
+---+---------------------------------------+-------------------------------------+---------------------------------+
| | Mother. | Father. | Offspring. |
|Pen+----+-----+---------------------+------+----+-----+------------------+-------+--------+-------+-------+--------+
|No.| No.| Gen.| Races. |Grade.| No.| Gen.| Races. |Grade. |Boot |Boot |Boot |P. ct. |
| | | | | | | | | |present.|slight.|absent.|absent. |
+---+----+-----+---------------------+------+----+----+-------------------+-------+--------+-------+-------+--------+
|608| 384| F1 |Wh. Legh. × Dk. Brah.| Pr. |409 |F1|Wh. Legh. × Dk. Brah.|Pr. | 36 | 5 | 3 | 6.8 |
|608| 248| F1 | Do. | Pr. |409 |F1| Do. |Pr. | 32 | 5 | 4 | 9.8 |
|608| 249| F1 | Do. | Pr. |409 |F1| Do. |Pr. | 39 | 11 | 13 | 20.6 |
|608| 395| F1 | Do. | Pr. |409 |F1| Do. |Pr. | 20 | 11 | 10 | 24.4 |
|608| 385| F1 | Do. | Pr. |409 |F1| Do. |Pr. | 20 | 6 | 14 | 35.0 |
| | | | +--------+-------+-------+--------+
| | | | Totals (229) | 147 | 38 | 44 | 19.2 |
| | | | +========+=======+=======+========+
|659| 762| F1 |Wh. Legh. × Dk. Brah.| Pr. |375 |F1|Wh. Legh. × Dk. Brah.|Pr. | 18 | 4 | 1 | 4.4 |
|659| 503| F1 | Do. | Pr. |375 |F1| Do. |Pr. | 23 | 6 | 2 | 6.5 |
|659| 382| F1 | Do. | Pr. |375 |F1| Do. |Pr. | 10 | 2 | 1 | 7.7 |
|659| 250| F1 | Do. | Pr. |375 |F1| Do. |Pr. | 33 | 7 | 5 | 11.1 |
|659| 737| F1 | Do. | Pr. |375 |F1| Do. Pr. | 19 | 2 | 3 | 12.5 |
|659| 387| F1 | Do. | Pr. |375 |F1| Do. Pr. | 16 | 6 | 4 | 15.4 |
| | | | +--------+-------+-------+--------+
| | | | Totals (162) | 119 | 27 | 16 | 9.9 |
| | | | +========+=======+=======+========+
|655| 720| F1 |Wh. Legh. × Dk. Brah.| Pr. |666 |F1|Wh. Legh. × Dk. Brah.|Pr. | 5 | 2 | .. | 0.0 |
|655| 724| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 6 | 1 | .. | 0.0 |
|655| 728| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 3 | 1 | .. | 0.0 |
|655| 730| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 4 | .. | .. | 0.0 |
|655| 732| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 9 | .. | .. | 0.0 |
|655| 734| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 3 | .. | .. | 0.0 |
|655| 761| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 6 | 2 | .. | 0.0 |
|655| 800| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 1 | .. | .. | 0.0 |
|655| 721| F1 | Do. | Pr. |666 |F1| Do. |Pr. | 9 | 1 | 1 | 9.1 |
| | | | +--------+-------+-------+--------+
| | | | Totals (54) | 46 | 7 | 1 | 1.9 |
| | | | +========+=======+=======+========+
|655| 724| F1 |Wh. Legh. × Dk. Brah.| Pr. |254 |F1|Wh. Legh. × Dk. Brah.|Pr. | 3 | .. | .. | 0.0 |
|655| 734| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 12 | 1 | .. | 0.0 |
|655| 800| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 13 | .. | 1 | 7.1 |
|655| 720| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 12 | .. | 1 | 7.7 |
|655| 728| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 8 | 1 | 1 | 10.0 |
|655| 761| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 17 | 4 | 4 | 16.0 |
|655| 732| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 8 | 1 | 2 | 18.2 |
|655| 730| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 7 | .. | 2 | 22.2 |
|655| 721| F1 | Do. | Pr. |254 |F1| Do. |Pr. | 9 | .. | 3 | 25.0 |
| | | | +--------+-------+-------+--------+
| | | | Totals (110) | 89 | 7 | 14 | 12.7 |
| | | | +========+=======+=======+========+
|632| 742| F1 |Min. × Dk. Brah. | Pr. |637 |F1|Min. × Dk. Brah. |Pr. | 4 | 1 | 0 | 0.0 |
|632| 690| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 27 | 6 | 1 | 2.9 |
|632| 631| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 32 | 11 | 2 | 4.4 |
|632| 618| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 35 | 8 | 2 | 4.4 |
|632| 700| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 18 | 3 | 2 | 8.7 |
|632| 703| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 14 | 11 | 3 | 10.7 |
|632| 743| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 22 | 2 | 3 | 11.1 |
|632| 599| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 23 | 8 | 4 | 11.4 |
|632| 524| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 18 | 6 | 5 | 17.2 |
|632| 576| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 14 | 9 | 6 | 20.7 |
|632| 638| F1 | Do. | Pr. |637 |F1| Do. |Pr. | 8 | 2 | 6 | 37.5 |
| | | | +--------+-------+-------+--------+
| | | | Totals (316) | 215 | 67 | 34 | 10.8 |
+---+----+-----+------------------------------------------------------------------+--------+-------+-------+--------+
+---+-------------------------------+--------------------------------+----------------------------------------------+
| | Mother. | Father. | Boot-grade in offspring. |
|Pen+----+-----+----------------+---+----+-----+-----------------+---+--+--+--+--+--+--+--+--+--+--+--+-----+-------+
|No.| No.| Gen.| Races. |Gr.| No.| Gen.| Races. |Gr.| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10|Aver-|P. ct. |
| | | | | | | | | | | | | | | | | | | | | age.|absent.|
+---+----+-----+----------------+---+----+-----+-----------------+---+--+--+--+--+--+--+--+--+--+--+--+-----+-------+
|801|2526| F1 |Min. × Dk. Brah.| 2 |5399| F1 |W. L. × Dr. Brah.| 8 |..|..|..|..| 1|..|..| 1|..|..| 1| 7.0 | 0.0 |
|801|2831| F1 | Do. | 4 |5399| F1 | Do. | 8 | 1| 1| 1| 4| 1| 7| 2| 2| 2|..| 2| 5.0 | 4.3 |
|801|1892| F1 | Do. | 3 |5399| F1 | Do. | 8 | 1| 1| 0| 1| 2|..| 1|..| 1| 1| 1| 5.0 |11.1 |
| | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+-------+
| | | | Totals (35) | 2| 2| 1| 5| 4| 7| 3| 3| 3| 1| 4| 5.2 | 5.71 |
+---+----+-----+-----------------------------------------------------+--+--+--+--+--+--+--+--+--+--+--+-----+-------+
TABLE 34.--_Distribution of boot-grade in the F2 generation of
booted × non-booted poultry_--Continued.
+-------------------------------------------------------------------------------------------------------------------+
| SILKIE CROSSES. |
+---+-------------------------------+-------------------------------+-----------------------------------------------+
| | Mother. | Father. | Boot-grade in offspring. |
|Pen+----+-----+----------------+---+----+-----+----------------+---+---+--+--+--+--+--+--+--+--+--+--+-----+-------+
|No.| No.| Gen.| Races. |Gr.| No.| Gen.| Races. |Gr.| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10|Aver-|P. ct. |
| | | | | | | | | | | | | | | | | | | | | age.|absent.|
+---+----+-----+----------------+---+----+-----+----------------+---+---+--+--+--+--+--+--+--+--+--+--+-----+-------+
|709|1955| F1 |Silkie × Spanish| 5 |1578| F1 |Silkie × Spanish| 0 | 5| 1| 2| 1| 1| 1| 1| 0| 0| 0| 0| 1.92| 41.7 |
|753|1966| F1 |Silkie × Min | 0 |2573| F1 |Min. × Silkie | 0 | 19| 4| 2| 2|..| 2| 2| 2| 1|..|..| 1.71| 55.9 |
|709|1963| F1 |Silkie × Spanish| 7 |1578| F1 |Silkie × Spanish| 0 | 23| 6| 1| 6| 7|..|..|..|..|..|..| 1.26| 53.5 |
|753|2575| F1 |Silkie × Min | 0 |2573| F1 |Silkie × Min. | 0 | 15| 3| 7|..|..|..|..|..|..|..|..| 0.68| 60.0 |
|753|2071| F1 | Do. | 0 |2573| F1 | Do. | 0 | 23| 4| 6|..|..|..|..|..|..|..|..| 0.49| 69.7 |
|709|1453| F1 | Do. | 1 |1578| F1 |Silkie × Spanish| 0 | 24|11| 3|..|..|..|..|..|..|..|..| 0.45| 63.2 |
|709|2223| F1 |Silkie × Spanish| 0 |1578| F1 | Do. | 0 | 32| 7| 3|..|..|..|..|..|..|..|..| 0.31| 76.2 |
| | | | +---+--+--+--+--+--+--+--+--+--+--+-----+-------+
| | | | Totals (227) |141|36|24| 9| 8| 3| 3| 2| 1| 0| 0| 0.87| 62.2 |
| | | | |===+==+==+==+==+==+==+==+==+==+==+=====+=======+
|830|4082| F1 |Silkie × W. Legh| 2 |3947| F1 |Silkie × W. Legh| 1 | 11| 8|..| 7| 1|..|..|..|..|..|..| 1.22| 40.7 |
|830|4079| F1 | Do. | 0 |3947| F1 | Do. | 1 | 18| 7| 6| 3|..|..|..|..|..|..|..| 0.82| 53.0 |
|830|5379| F1 | Do. | 0 |3947| F1 | Do. | 1 | 18| 4| 5| 3|..|..|..|..|..|..|..| 0.77| 60.0 |
|830|4081| F1 | Do. | 0 |3947| F1 | Do. | 1 | 24| 6|10| 1|..|..|..|..|..|..|..| 0.71| 58.5 |
|830|5374| F1 | Do. | 0 |3947| F1 | Do. | 1 | 11| 3| 3| 1|..|..|..|..|..|..|..| 0.67| 61.1 |
|830|3946| F1 | Do. | 0 |3947| F1 | Do. | 1 | 19| 1|..|..| 1|..|..|..|..|..|..| 0.24| 90.5 |
| | | | |===+==+==+==+==+==+==+==+==+==+==+=====+=======+
| | | | Totals (170) |101|29|24|14| 2| 0| 0| 0| 0| 0| 0| 0.75| 59.4 |
+---+----+-----+----------------------------------------------------+---+--+--+--+--+--+--+--+--+--+--+-----+-------+
The distribution of table 35 is characterized by its large
variability. Although the numbers are small, there are evidences of
two modes, one between grades 3 and 6, and the other at from 8 to 10;
these evidently correspond to the modes of the typical Silkie and
the typical Cochin respectively or to DR and RR types of booting
respectively. The distribution of table 35 is additional evidence of
the heterozygous nature of the Silkie boot.
TABLE 35.--_Distribution of boot-grades in Silkie × Cochin crosses._
+---+------------------------------+--------------------------------+-----------------------------------------------------------+
| | Mother. | Father. | Boot-grades in offspring. |
|Pen+----+----+--------------+-----+------+----+--------------+-----+--+---+---+---+---+---+---+---+---+---+----+-----+---------+
|No.| No.|Gen.| Races. | Gra.| No. |Gen.| Races. | Gra.| 0| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Av. | P. ct. |
| | | | | | | | | | | | | | | | | | | | | | abs. |
+---+----+----+--------------+-----+------+----+--------------+-----+--+---+---+---+---+---+---+---+---+---+----+-----+---------+
|821|5925| F1 | Silk. × Coch.| 7 | 6095 | F1 | Silk. × Coch.| 7 |..| ..| ..| ..| 1 |.. | ..| 1 | 3 | 1 | 1 | 7.7 | 0.0 |
|821|7408| F1 | Do. | 4 | 6095 | F1 | Do. | 7 |..| ..| ..| 1| 2 | 2 | 3 | ..| 2 | 1 | 2 | 6.5 | 0.0 |
|821|7413| F1 | Do. | 3 | 6095 | F1 | Do. | 7 | 2| 0| 3| 1| 0 | 1 | 1 | 0 | 0 | 1 | 1 | 3.9 | 20.0 |
|821|7416| F1 | Do. | 5 | 6095 | F1 | Do. | 7 |..| ..| ..| 3| 1 | 0 | 4 | 0 | 3 | 3 | 2 | 6.8 | 0.0 |
|821|7417| F1 | Do. | .. | 6095 | F1 | Do. | 7 |..| ..| ..| ..|.. |.. | ..| 1 |.. | 1 | 4 | 9.3 | 0.0 |
|821|7418| F1 | Do. | 4 | 6095 | F1 | Do. | 7 |..| ..| 1| ..| 2 | 1 | 1 | 1 | 1 |.. | 1 | 5.8 | 0.0 |
|821|7423| F1 | Do. | 6 | 6095 | F1 | Do. | 7 |..| ..| ..| 1|.. | 2 | ..| 2 | 2 |.. | 2 | 7.0 | 0.0 |
|821|7428| F1 | Do. | .. | 6095 | F1 | Do. | 7 | 1| ..| ..| ..|.. | 1 | ..| ..| 1 |.. |.. | 4.3 | 33.3 |
|821|7429| F1 | Do. | 8 | 6095 | F1 | Do. | 7 |..| ..| ..| 1| 1 | 1 | ..| ..|.. | 1 | 1 | 6.2 | 0.0 |
| | | | +--+----+--+---+---+---+---+---+---+---+----+-----+---------+
| | | | Totals (77) | 3| 0| 4| 7| 7 | 8 | 9 | 5 |12 | 8 |14 |6.42 | 3.90 |
| | | | |\--------------------/|\------------------/| | |
| | | | | 29 | 48 | | |
+---+----+----+-----------------------------------------------------+----------------------+--------------------+-----+---------+
We are now in a position to consider the effect of back crosses
(table 36). The contrast between the totals in tables 36 and
37 is very great. The strict Mendelian expectation is: in the
DR × D crosses 50 per cent DD (clean-footed) and 50 per cent
heterozygous, which, with imperfect dominance, might be expected to
show foot-feathering. Actually about 46 per cent are clean-footed.
In the DR × R crosses expectation is that 50 per cent certainly
(the extracted recessives) and 50 per cent more possibly will have
the shanks feathered, on account of imperfect dominance of the
heterozygotes. Actually all have feathered feet. These statistics
thus confirm the view of the dominance of the inhibiting factor.
Were clean shank recessive, then the DR × R crosses must give
50 per cent clean-footed and probably over. The actual result, none
clean-footed, is not in accord with the latter assumption.
TABLE 36.--_Distribution of boot-grade in DR × D (non-booted)
crosses._
+---+-----------------------------------------+---------------------------+--------------------------------------+
| | Mother. | Father. | Boot-grade in offspring. |
| +---+-----+----------------------+--------+---+----+---------+--------+---------+--------+--------+----------+
|Pen| | | | | | | | | | | | |
|No.|No.| Gen.| Races. | Grade. |No.|Gen.| Race. | Grade. | Present.| Slight.| Absent.| Per cent.|
| | | | | | | | | | | | | present. |
+---+---+-----+----------------------+--------+---+----+---------+--------+---------+--------+--------+----------+
|653|508| F1 | Wh. Legh. × Bf. Coch.| Pr. |117| P. | Game. | 0 | 3 | 4 | 6 | 46.2 |
|653|508| F1 | Do. | Pr. |116| P. | Do. | 0 | 6 | 5 | 4 | 26.7 |
|653|577| F1 | R × Bf. Coch. | 3 |117| P. | Do. | 0 | 1 | 0 | 7 | 87.5 |
|653|577| F1 | Do. | 3 |116| P. | Do. | 0 | 1 | 3 | 2 | 33.3 |
|653|587| F1 | Do. | 1 |117| P. | Do. | 0 | 1 | 2 | 4 | 57.1 |
|653|587| F1 | Do. | 1 |116| P. | Do. | 0 | 3 | 3 | 2 | 25.0 |
|653|635| F1 | Do. | 3 |117| P. | Do. | 0 | .. | 1 | 6 | 85.7 |
|653|635| F1 | Do. | 3 |116| P. | Do. | 0 | 2 | 2 | 1 | 20.0 |
|653|652| F1 | Do. | 5 |117| P. | Do. | 0 | 5 | 8 | 4 | 23.5 |
|653|652| F1 | Do. | 5 |116| P. | Do. | 0 | 1 | 2 | 2 | 40.0 |
|653|691| F1 | Do. | Pr. |117| P. | Do. | 0 | 2 | 2 | 1 | 20.0 |
|653|705| F1 | Do. | 2 |117| P. | Do. | 0 | 3 | 2 | 5 | 50.0 |
|653|705| F1 | Do. | 2 |116| P. | Do. | 0 | 1 | 1 | 5 | 71.4 |
|653|713| F1 | Do. | Pr. |117| P. | Do. | 0 | .. | 0 | 4 | 100.0 |
|653|713| F1 | Do. | Pr. |116| P. | Do. | 0 | 1 | 1 | 3 | 60.0 |
|653|760| F1 | Do. | Pr. |117| P. | Do. | 0 | 2 | 2 | 6 | 60.0 |
|653|760| F1 | Do. | Pr. |116| P. | Do. | 0 | 0 | 3 | 2 | 40.0 |
|653|799| F1 | Do. | 3 |117| P. | Do. | 0 | 2 | 0 | 3 | 60.0 |
| | | | +---------+--------+--------+----------+
| | | | Total (143) | 34 | 42 | 67 | 46.9 |
| | | | |=======================================
|661|635| F1 | Bf. Coch. × Game. | Pr. |466| P. | Game. | 0 | 1 | .. | 2 | 66.7 |
|661|635| F1 | Do. | Pr. |428| P. | Do. | 0 | 2 | .. | 1 | 33.3 |
|661|691| F1 | Do. | Pr. |466| P. | Do. | 0 | 2 | .. | 2 | 50.0 |
|661|691| F1 | Do. | Pr. |428| P. | Do. | 0 | 2 | .. | 1 | 33.3 |
|661|799| F1 | Do. | Pr. |466| P. | Do. | 0 | 3 | .. | 2 | 40.0 |
|661|799| F1 | Do. | Pr. |428| P. | Do. | 0 | 4 | .. | 1 | 20.0 |
| | | | +---------+--------+--------+----------+
| | | | Total (23) | 14 | 0 | 9 | 39.1 |
| | | | Grand Total (166) | 48 | 42 | 76 | 45.8 |
+-------+-----+-----------------------------------------------------------+---------+--------+--------+----------+
TABLE 37.--_Distribution of boot-grade in DR × RR (booted) crosses._
+----+--------------------+-----+------------------------------+---------------------------------------------+----+
| | Mother. | | Father. | Boot-grade in offspring. | |
| +-----+-----+--------+-----+-----+--------+----------+----+---+---+---+---+----+----+----+----+----+----+----+
|Pen | | | | | | | | | | | | | | | | | | | |
|No. | | | | | | | | | | | | | | | | | | | |
| | No. | Gen.| Race. | Gr. | No. | Gen. | Race. | Gr.| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
+----+-----+-----+--------+-----+-----+--------+----------+----+---+---+---+---+----+----+----+----+----+----+----+
|851 | 838 | P. | Cochin.| 8 |7526 |[A]F1 | Silkie. | 3 |.. |.. |.. | 3 | 2 | 4 | 3 | .. | .. | 2 | 2 |
|851 | 840 | P. | Do. | 10 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | 1 | .. | 1 | .. | .. | 1 | .. |
|851 | 841 | P. | Do. | 10 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | 1 | .. | 1 | .. | 1 | .. | .. |
|851 |1002 | P. | Do. | 8 |7526 | F1 | Do. | 3 |.. |.. |.. | 3 | 1 | 2 | 1 | 2 | 3 | 1 | 1 |
|851 |2073 | P. | Do. | 7 |7526 | F1 | Do. | 3 |.. |.. | 1 | 1 | 1 | .. | 1 | 1 | 1 | 3 | 2 |
|851 |2299 | P. | Do. | 9 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | 2 | 2 | 1 | 1 | .. | .. | 2 |
|851 |3410 | P. | Do. | 9 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | .. | 4 | 3 | 2 | 1 | 5 | 1 |
|851 |5567 | P. | Do. | 9 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | 2 | .. | .. | .. | 3 | 3 | 5 |
|851 |6956 | P. | Do. | 8 |7526 | F1 | Do. | 3 |.. |.. |.. |.. | 3 | 3 | .. | 2 | 2 | .. | 5 |
| | | | ====================================================
| | | | Totals (99) ..... | 0 | 0 | 1 | 7 | 13 | 15 | 11 | 8 | 11 | 15 | 18 |
+----+-----+-----+---------------------------------------------+---+---+---+---+----+----+----+----+----+---------+
[A] Pure-blooded Silkie assumed heterozygous to boot.
Numerous observations have been made upon the progeny of parents
belonging to hybrid generations beyond the first. Owing to the
extreme imperfection of dominance it is rarely possible to say
with certainty from inspection whether a given bird has germ-cells
dominant or recessive, or both, with reference to booting; only
breeding enables us to make a decision. There is an exception,
however, in the case of pure extracted recessives. They are
distinguished by heavy booting and produce only booted offspring. I
propose to give, in detail, the matings of these later generations
and their progeny, the families being arranged in decreasing order of
average grade of booting (table 38).
TABLE 38.--_Distribution of boot-grades in offspring of parents
one or both of which belong to a hybrid generation beyond the
first._
B = Brahma; C = Cochin; G = Game; L = Leghorn; M = Minorca; S =
Silkie; Sp = Spanish; T = Tosa; WL = White Leghorn
+------+---+------------------------+------------------------+-------+-------------------------------------+
|Serial|Pen| Mother. | Father. |Mating.| Boot-grade in offspring. |
| No. |No.+----+-----+---------+---+----+-----+---------+---+ +--+--+--+--+--+--+--+--+--+--+--+----+
| | | No.| Gen.| Races. |Gr.| No.| Gen.| Races. |Gr.| | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10| Av.|
+------+---+----+-----+---------+---+----+-----+---------+---+-------+--+--+--+--+--+--+--+--+--+--+--+----+
| 1 |814| 354| F1 |B × T | 7|3975| F2 |B × T | 9 |R × R |..|..|..|..|..|..|..|..|..|10|15|9.6 |
| 2 |801| 181| F1 | Do. | 4|5399| F2 |M × B | 8 | Do. |..|..|..|..|..|..|..|..|..| 1| 1|9.5 |
| 3 |814| 300| F1 | Do. | 5|3975| F2 |B × T | 9 | Do. |..|..|..|..|..|..|..|..| 1| 3| 4|9.4 |
| 4 |801|4569| F2 | Do. | 6|4562| F2 | Do. | 7 | Do. |..|..|..|..|..|..|..|..| 1| 1| 2|9.3 |
| 5 |814|5523| F2 | Do. | 9|3975| F2 | Do. | 9 | Do. |..|..|..|..|..| 1|..|..| 3| 4| 9|9.1 |
| 6 |814|4560| F2 | Do. | 8|3975| F2 | Do. | 9 | Do. |..|..|..|..|..| 1| 1| 1|..| 2| 7|8.8 |
| 7 |814| 190| F1 | Do. | 2|3975| F2 | Do. | 9 | Do. |..|..|..|..|..|..| 1| 1| 1| 1| 4|8.8 |
| 8 |806|4325| F3 |M × B | 7|5257| F3 |M × B | 9 | Do. |..|..|..|..|..|..| 1| 1| 2| 2| 3|8.6 |
| 9 |806|5913| F3 | Do. | 7|5257| F3 | Do. | 9 | Do. |..|..|..|..| 1|..|..| 1| 4| 2| 3|8.3 |
| 10 |732|1235| F2 | Do. | 8|2732| F2 | Do. | 6 | Do. |..|..|..|..|..|..| 1| 2| 4| 3|..|7.9 |
| 11 |806|4052| F3 | Do. | 5|5257| F3 | Do. | 5 | Do. |..|..|..|..| 1| 1|..| 3|..| 6| 1|7.8 |
| 12 |776|1132| F2 |C × WL | 3|2732| P. |C | 8 |DR × R |..|..|..| 1| 1| 1| 1| 3| 6| 8|..|7.6 |
| 13 |801|6869| F1.5|B × F1 | 6|4562| F2 |M × B | 7 |R × R |..|..|..|..|..| 1| 1| 2| 1| 1| 1|7.4 |
| 14 |814| 186| F1 |T × B | 4|3975| F2 |B × T | 9 |DR × R |..| 2| 1| 0| 1| 3| 0| 1| 3| 6| 5|7.2 |
| 15 |814|4683| F2 | Do. | 2|3975| F2 | Do. | 9 | Do. |..|..|..|..| 3| 2| 3| 1| 1| 1| 5|7.1 |
| 16 |767|2104| F2 |WL × B | 3|3116| F1 | Do. | 9 | Do. |..|..|..| 1| 4| 1| 2| 7| 6| 1| 0|7.1 |
| 17 |801|2526| F1 | Do. | 2|5399| F2 |M × B | 8 | Do. |..|..|..|..| 1|..|..| 1|..|..| 1|7.0 |
| 18 |806|3936| F2 |M × B | 10|5257| F3 | Do. | 9 |R × R |..|..|..|..| 1|..| 2|..| 2|..| 1|7.0 |
| 19 |839|5383| F2 |L × M × B| 2|4348| F2 |L × M × B| 3 |DR × DR|..|..|..|..| 1| 1|..|..|..| 1| 1|7.0 |
| 20 |801|5515| F2 |B × T | 4|5399| F2 |M × B | 8 |DR × R |..|..|..| 1| 1| 2| 2|..| 1| 1| 3|6.9 |
| 21 |732|1003| F2 |M × B | 9|2442| F2 | Do. | 6 |R × R |..|..|..|..| 3| 7| 7| 7| 7| 5| 2|6.8 |
| 22 |839|1892| F1.5|L × M × B| 6|4348| F2 |L × M × B| 3 |R × DR |..|..|..| 2| 1|..| 1|..|..| 2| 2|6.8 |
| 23 |806|4196| F3 |M × B | 2|5257| F3 |M × B | 9 |DR × R |..|..|..| 2| 2| 2| 1|..|..| 3| 3|6.7 |
| 24 |801|2526| F1 |WL × B | 2|5399| F2 | Do. | 8 | Do. |..|..|..|..| 1|..|..| 1|..| 1| 0|6.7 |
| 25 |801|6861| F2.5|B × T | 7|4562| F2 | Do. | 7 |R × R |..|..|..|..|..| 2| 1|..|..|..| 1|6.5 |
| 26 |767| 872| F2 | Do. | 5|3116| F1 |B × T | 9 |DR × R | 1| 0| 0| 1| 4| 6| 9| 4| 4| 6| 3|6.5 |
| 27 |801|4263| F2 | Do. | 3|4562| F2 |M × B | 7 | Do. |..|..|..| 2| 3|..| 3| 1| 1| 4| 1|6.5 |
| 28 |767| 181| F1 | Do. | 4|3166| F1 |B × T | 9 | Do. |..|..| 1| 2| 6|13|11| 5|11| 8| 3|6.5 |
| 29 |814| 862| F2 | Do. | 1|3975| F2 | Do. | 9 | Do. |..|..|..| 2| 2| 5| 2| 1| 1| 3| 2|6.3 |
| 30 |801| 872| F2 | Do. | 5|5399| F2 |M × B | 8 | Do. |..|..|..| 1| 3| 8| 5| 2|..| 2| 4|6.3 |
| 31 |839|5389| F2 |M × B | 7|4348| F2 | Do. | 3 |R × DR |..|..|..| 6| 4| 1| 0| 1| 1| 1| 6|6.2 |
| 32 |801| 872| F2 |B × T | 5|4562| F2 | Do. | 7 |DR × R |..|..|..| 1| 5| 4| 3| 1| 2| 2| 2|6.1 |
| 33 |767| 190| F1 | Do. | 4|3116| F1 |B × T | 9 | Do. |..|..|..| 5| 6|11|12| 7| 4| 9|..|6.1 |
| 34 |801|1892| F1 |M × B | 3|4562| F2 |M × B | 7 | Do. |..|..| 1|..|..|..| 1|..| 2|..|..|6.0 |
| 35 |801|5515| F2 |B × T | 4|4562| F2 | Do. | 7 | Do. |..|..| 1|..|..| 1| 3|..| 1| 1|..|6.0 |
| 36 |731| 248| F1 |M × B | 4|1249| F2 |WL × B | 7 | Do. |..|..| 2| 3| 3|..| 2|..|..| 5| 2|6.0 |
| 37 |732|1228| F2 | Do. | 8|2442| F2 |M × B | 6 |R × R |..|..|..| 2| 8| 5| 6| 2| 8| 3|..|6.0 |
| 38 |732| 690| F1 | Do. | 5|2442| F2 | Do. | 6 |DR × R | 2| 0| 6| 2| 5| 5| 7|16|10| 6|..|6.0 |
| 39 |751|1919| F2 |WL × B | 8|1139| F2 |L × B | 8 |R × R |..|..|..| 5| 4| 6| 6| 1|11| 1|..|5.9 |
| 40 |732| 618| F1 |M × B | 8|2442| F2 |M × B | 6 |DR × R |..| 1| 2| 3| 2| 5| 3| 5| 9| 1|..|5.8 |
| 41 |731|1245| F2 |WL × B | 9|1249| F2 |WL × B | 7 |R × R |..|..| 1| 2| 1| 8| 2| 3| 6|..|..|5.8 |
| 42 |760| 354| F1 |B × T | 5|1270| F2 |B × T | 2 |R × DR |..|..| 1| 3| 9| 5| 8| 4| 7| 2|..|5.7 |
| 43 |701|1915| F2 |WL × B | 8|1898| F2 |WL × B | 3 | Do. |..|..|..|..| 7| 4| 3| 2| 3| 1|..|5.7 |
| 44 |801|6869| F1.5|B (M × B)| 6|5399| F2 | Do. | 8 |DR × R |..|..|..| 1|..| 1|..|..|..| 1|..|5.7 |
| 45 |801|4570| F2 |B × T | 2|4562| F2 | Do. | 7 | Do. |..|..| 1| 2| 5| 3| 1| 1| 1| 4|..|5.6 |
| 46 |814| 703| F1 | Do. | 4|3975| F2 |B × T | 9 | Do. |..|..| 3| 5| 2| 7| 5| 6| 2| 4|..|5.5 |
| 47 |732| 953| F2 |M × B | 3|2442| F2 |M × B | 6 | Do. |..| 2| 2| 3| 8| 9| 5| 3| 7| 6|..|5.5 |
| 48 |801|7528| F1 | Do. | 4|4562| F2 | Do. | 8 | Do. |..|..|..| 1| 4| 2| 1|..| 1|..| 1|5.3 |
| 49 |731|2116| F2 | Do. | 10|1249| F2 |WL × B | 7 |R × R |..| 1| 1| 1| 2| 3| 0| 2| 2| 1|..|5.2 |
| 50 |745|2115| F2 |C × T | 4|1258| F2 |B × T | 4 |DR × DR|..|..|..| 2| 1| 6| 4| 2|..|..|..|5.2 |
| 51 |801|6843| F2 |B × T | 3|4562| F2 | Do. | 8 |DR × R |..|..|..|..| 3| 2| 1|..| 1|..|..|5.1 |
| 52 |801|2831| F1 |M × B | 4|5399| F2 | Do. | 8 | Do. | 1| 1| 1| 4| 1| 7| 2| 2| 2|..| 2|5.0 |
| 53 |801|1892| F1 | Do. | 3|5399| F2 | Do. | 8 | Do. | 1| 1|..| 1| 2|..| 1| 0| 1| 1| 1|5.0 |
| 54 |801|7528| F1 | Do. | 4|4562| F2 | Do. | 8 | Do. |..|..|..| 1| 2| 1| 1|..| 1|..|..|5.0 |
| 55 |731|1755| F2 |WL × B | 6|1249| F2 |WL × B | 7 |R × R |..|..|..|..| 2| 1| 4| 1| 2|..|..|5.0 |
| 56 |745|2513| F3 |C × T | 4|1258| F2 |B × T | 4 |DR × DR|..|..|..|..| 2| 5| 2|..| 3| 1|..|5.0 |
| 57 |839|3950| F2 |M × B | 4|4348| F2 |M × B | 3 | Do. |..| 2| 3| 3| 2| 4| 1| 1| 1| 2| 2|4.95|
| 58 |754| 873| F2 |B × T | 3| 871| F2 |B × T | 2 | Do. | 1| 2| 1| 4| 1|..|..|..| 8|..|..|4.94|
| 59 |806| 599| F2 |M × B | 3|5257| F2 |M × B | 7 |DR × R |..|..| 2| 1| 2| 2| 1|..| 1|..|..|4.86|
| 60 |760| 300| F1 |B × T | 7|1270| F2 |B × T | 2 |R × DR |..|..| 2|19| 8|13| 6| 4| 5| 2| 1|4.83|
| 61 |806|4456| F2 |M × B | 1|5257| F3 |M × B | 7 |DR × R |..| 1| 1| 1| 1|..| 1|..| 1| 1|..|4.71|
+------+---+----+-----+---------+---+----+-----+---------+---+-------+--+--+--+--+--+--+--+--+--+--+--+----+
TABLE 38.--_Distribution of boot-grades in offspring of parents
one or both of which belong to a hybrid generation beyond the
first_--Continued.
B = Brahma; C = Cochin; G = Game; L = Leghorn; M = Minorca; S =
Silkie; Sp = Spanish; T = Tosa; WL = White Leghorn.
+------+---+------------------------+-----------------------+--------+--------------------------------------+
| | | Mother. | Father. | | Boot-grade in offspring. |
|Serial|Pen|----+-----+---------+---+----+-----+--------+---+ Mating.+--+--+--+--+--+--+--+--+--+--+--+-----+
| No. |No.| No.| Gen.| Races. |Gr.| No.| Gen.| Races. |Gr.| | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10| Av. |
+------+---+----+-----+---------+---+----+-----+--------+---+--------+--+--+--+--+--+--+--+--+--+--+--+-----+
| 62 |732|2407| F2 |M × B | 2|2442| F2 |M × B | 6 | DR × R |..|..| 1| 3| 4| 1| 1| 2|..| 1|..| 4.69|
| 63 |701| 894| F2 |L × B | 7|1898| F2 |L × B | 3 | R × DR | 1| 1| 2| 8| 6| 1| 2| 2| 4| 2|..| 4.62|
| 64 |760| 994| F2 |B × T | 3|1270| F2 |B × T | 3 | DR × DR|..|..|..|..| 4| 2| 1|..|..|..|..| 4.57|
| 65 |760| 981| F2 | Do. | 3|1270| F2 | Do. | 3 | Do. | 1|..| 3| 6| 1| 4| 2| 7|..|..|..| 4.54|
| 66 |701|1772| F2 |L × B | 6|1898| F2 |L × B | 3 | R × DR |..|..|..| 4| 7| 2| 2| 2|..|..|..| 4.47|
| 67 |839|3541| F1 |M × B | 6|4348| F2 |M × B | 3 | DR × DR| 4| 1| 4|..|..| 4| 2|..| 2| 1| 2| 4.30|
| 68 |842|1645| F2 | Do. | 2|4385| F2 | Do. | 4 | Do. | 3| 2| 6| 5| 6| 6| 3| 0| 2| 4| 1| 4.29|
| 69 |770|2049| F2 |L × B | 3| 926| F2 | Do. | 3 | Do. | 9| 3| 1| 6| 8| 2| 6| 6| 3| 1| 3| 4.29|
| 70 |731|2577| F1.5|L × C | 4|1249| F2 |L × B | 7 | DR × R |..|..| 2| 2| 3| 2| 2| 1|..|..|..| 4.25|
| 71 |701| 250| F1 |L × B | 3|1898| F2 | Do. | 3 | DR × DR| 3| 3| 5| 8|12|10|10| 6| 1|..|..| 4.22|
| 72 |701|1335| F2 |T × L × B| 8|1898| F2 | Do. | 3 | R × DR |..|..| 1| 9| 6| 6| 4| 1|..|..|..| 4.22|
| 73 |806|4767| F3 |M × B | 3|5257| F3 |M × B | 7 | DR × R |..|..| 1|..| 2| 1| 1|..|..|..|..| 4.20|
| 74 |740|1439| F2 |C × L | 2|1145| F2 |C × L | 3 | DR × DR| 3|..| 1| 3| 6| 4| 2|..| 2| 1|..| 4.18|
| 75 |754|3126| F2 |B × T | 4| 871| F2 |B × T | 3 | Do. |..| 2| 5|11| 7|10| 5| 0| 2| 1|..| 4.14|
| 76 |770|1645| F2 |M × B | 4| 926| F2 |M × B | 3 | Do. | 3| 2| 1| 9| 5| 5| 2| 2| 3| 1|..| 4.10|
| 77 |731| 249| F1 |L × B | 3|1249| F2 |L × B | 7 | DR × R | 7| 4| 6| 5| 7| 5| 9| 3| 6| 1|..| 4.08|
| 78 |732| 703| F1 |M × B | 3|2442| F2 |M × B | 6 | Do. | 1| 3|13|13| 8| 6| 7| 6| 3|..|..| 4.07|
| 79 |770| 720| F1 |B × L | 4| 926| F2 | Do. | 3 | DR × DR| 6| 1| 3| 9| 5| 4| 5| 1| 4| 1| 1| 4.05|
| 80 |732|2441| F2 |M × B | 0|2442| F2 | Do. | 6 | DR × R |..| 1| 6| 8| 2| 6| 0| 3| 1|..|..| 4.00|
| 81 |760|1042| F2 |B × T | 3|1270| F2 |B × T | 2 | DR × DR| 2| 3| 3| 9| 3| 5| 8| 2| 0| 1|..| 4.00|
| 82 |731| 384| F1 |L × B | 4|1249| F2 |L × B | 7 | DR × R | 2| 1| 4| 4| 3| 2| 4| 0| 1| 1|..| 3.82|
| 83 |814|4566| F2 |B × T | 2|3975| F2 |B × T | 9 | Do. | 1| 4| 2| 4| 3| 2| 1|..|..|..|..| 3.82|
| 84 |732| 599| F1 |M × B | 3|2442| F2 |M × B | 6 | Do. | 6| 5|23|10| 5| 3| 4| 5| 8| 3| 1| 3.78|
| 85 |770| 761| F1 |B × L | 3| 926| F2 | Do. | 3 | DR × DR| 7| 3| 5| 3| 7| 7| 2| 6| 1| 1|..| 3.71|
| 86 |731|1770| F2 | Do. | 7|1249| F2 |L × B | 7 | DR × R | 1|..| 8| 6| 9| 3| 2|..| 2|..|..| 3.65|
| 87 |861|5165| F2 |T × C | 10| 95| F1 |T × C | 5 | R × DR |..|..|..|10| 3| 2| 1|..|..|..|..| 3.63|
| 88 |754|3175| F2 |B × T | 2| 871| F2 |B × T | 2 | DR × DR| 1|..| 2| 1| 3| 4|..|..|..|..|..| 3.55|
| 89 |731|2102| F2 |L × B | 1|1249| F2 |L × B | 7 | DR × R | 1| 0| 4| 2| 4| 1| 1| 1|..|..|..| 3.43|
| 90 |840|1755| F2 |M × B | 6|4177| F2 | Do. | 2 | R × DR |..|..| 6| 7| 7| 3| 1|..|..|..|..| 3.42|
| 91 |701|2576| F2 |L × B | 2|1898| F2 | Do. | 3 | DR × DR| 2| 1| 1| 8|11| 2| 1|..|..|..|..| 3.35|
| 92 |842|2049| F1 | Do. | 3|4385| F2 |M × B | 4 | Do. |11| 1| 2| 8| 5| 3| 1| 0| 2| 2| 2| 3.35|
| 93 |754| 853| F2 |B × T | 1| 871| F2 |B × T | 3 | Do. | 2| 3| 4| 6| 4| 1| 6|..|..|..|..| 3.31|
| 94 |826|2652| F1 |M × B | 3|4093| F2 |M × B | 0 | Do. | 8| 2| 1| 8| 1|..|..| 1| 2| 3|..| 3.28|
| 95 |754|1052| F2 |B × T | 2| 871| F2 |B × T | 2 | Do. | 3|..| 7| 9| 9| 5| 2|..|..|..|..| 3.26|
| 96 |701| 965| F2 |T × L × B| 0|1898| F2 |L × B | 3 | Do. | 1| 4| 6|12| 8| 4| 0| 2| 0|..|..| 3.19|
| 97 |732|1833| F2 |M × B | 1|2442| F2 |M × B | 6 | DR × R | 1| 1| 7| 6| 6| 4| 1|..|..|..|..| 3.19|
| 98 |732| 631| F1 | Do. | 3|2442| F2 | Do. | 6 | Do. | 3| 4|10|16|12| 4| 1| 2|..|..|..| 3.08|
| 99 |754| 862| F2 |B × T | 1| 871| F2 |B × T | 2 | DR × DR| 1| 5|10|17|10| 4| 1|..|..|..|..| 2.96|
| 100 |837|5641| F2 |T × L × B| 0|4288| F3 |L × B | 2 | Do. | 1| 2| 2| 3|..| 2|..| 1|..|..|..| 2.91|
| 101 |840|3841| F2 |L × B | 0|4177| F2 | Do. | 2 | D × DR | 3| 3| 2| 6| 4| 2|..|..|..|..|..| 2.86|
| 102 |701| 721| F1 | Do. | 2|1898| F2 | Do. | 3 | DR × DR| 2| 4| 3| 8| 3| 2| 2|..|..|..|..| 2.83|
| 103 |839|3949| F2 | Do. | 4|4348| F2 | Do. | 3 | Do. | 1| 2|..|..| 1| 1| 1|..|..|..|..| 2.83|
| 104 |840| 732| F1 | Do. | 3|4177| F2 | Do. | 2 | Do. | 7| 6| 9| 8| 7| 2| 1| 2|..| 1|..| 2.67|
| 105 |840| 249| F1 | Do. | 3|4177| F2 | Do. | 2 | Do. | 7| 3| 5| 6| 2| 9|..|..|..|..|..| 2.62|
| 106 |840|3916| F1.5| Do. | 2|4177| F2 | Do. | 2 | Do. | 5| 1| 4| 2| 2| 2| 1|..|..|..|..| 2.29|
| 107 |842|4945| F2 |M,L × B | 1|4385| F2 |M × B | 4 | Do. | 9| 3| 6| 5| 1| 2| 4|..|..|..|..| 2.27|
| 108 |731|2595| F2 |L × B | 1|1249| F2 |L × B | 7 | D × R | 6| 6| 7| 1|..|..|..|..|..|..|..| 2.15|
| 109 |840|5169| F2 | Do. | 3|4177| F2 | Do. | 2 | DR × DR| 6| 2| 5| 5| 2| 2|..|..|..|..|..| 2.05|
| 110 |837|5667| F3 | Do. | 2|4288| F3 | Do. | 2 | Do. | 2| 1| 2|..| 1| 1|..|..|..|..|..| 2.00|
| 111 |749|1355| F2 |G × C | 2|1854| F2 |G(C × L)| 0 | DR × D |..| 2| 5| 1|..|..|..|..|..|..|..| 1.87|
| 112 |824|3901| F2 |M × S | 1|5095| F2 |M × S | 1 | DR × DR|17| 3| 2| 3|..| 2|..|..| 1| 2|..| 1.73|
| 113 |751|1254| F2 |L × B | 0|1139| F2 |L × B | 8 | D × R |17| 5| 5| 4| 3| 3|..| 1|..|..|..| 1.63|
| 114 |749| 816| F1 | Do. | 2|1854| F2 |G(C × L)| 0 | DR × D | 6| 7| 3| 5| 1|..|..|..|..|..|..| 1.45|
| 115 |749| 929| F2 |G × C | 0|1854| F2 | Do. | 0 | D × D | 8| 3| 1|..|..|..| 1|..|..| 1|..| 1.43|
| 116 |749| 819| F1 |L × B | 1|1854| F1.5|G(C × L)| 0 | DR × D | 9| 3| 5| 3|..|..|..|..|..|..|..| 1.10|
| 117 |804|5099| F2 |S × Sp | 0|3823| F1 |S × Sp | 0 | D × D | 2|..|..| 1|..|..|..|..|..|..|..| 1.00|
| 118 |804|6043| F2 | Do. | 1|3823| F1 | Do. | 0 | Do. |..| 1|..|..|..|..|..|..|..|..|..| 1.00|
| 119 |817|5730| F1 |L × Sp | 0|3900| F2 | Do. | 1 | D × DR | 3| 3| 1|..|..|..|..|..|..|..|..| 0.71|
| 120 |817|4696| F1 | Do. | 0|3900| F2 | Do. | 1 | Do. | 9| 7| 3|..|..|..|..|..|..|..|..| 0.68|
| 121 |817|6046| F2 |S × M | 0|3900| F2 | Do. | 1 | Do. |10|..| 3|..|..|..|..|..|..|..|..| 0.46|
| 122 |817|6833| F1.5|L(G × S) | 0|3900| F2 | Do. | 1 | Do. | 6| 2| 1|..|..|..|..|..|..|..|..| 0.44|
| 123 |817|5062| F1 |L(Sp) | 0|3900| F2 | Do. | 1 | Do. |18| 7| 2|..|..|..|..|..|..|..|..| 0.41|
| 124 |817|5069| F1 | Do. | 0|3900| F2 | Do. | 1 | Do. |21| 7| 2|..|..|..|..|..|..|..|..| 0.37|
| 125 |817|6406| F1 | Do. | 0|3900| F2 | Do. | 1 | Do. |25| 8| 2|..|..|..|..|..|..|..|..| 0.34|
| 126 |817|7047| F1 | Do. | 0|3900| F2 | Do. | 1 | Do. | 4| 2|..|..|..|..|..|..|..|..|..| 0.33|
| 127 |749|2651| F2 |G × C | 0|1854| F2 |G(C × L)| 0 | D × D | 2| 1|..|..|..|..|..|..|..|..|..| 0.33|
| 128 |824|4714| F2 |S × Sp | 0|5095| F2 |M × S | 1 | Do. |26| 6| 1| 1|..|..|..|..|..|..|..| 0.32|
| 129 |817|4690| F1 | Do. | 0|3900| F2 |S × Sp | 1 | D × DR |21| 6| 1|..|..|..|..|..|..|..|..| 0.29|
| 130 |824|7439| F2 | Do. | 0|5095| F2 |M × S | 1 | D × D |11| 4|..|..|..|..|..|..|..|..|..| 0.27|
| 131 |804|4715| F2 | Do. | 0|3823| F1 |S × Sp | 0 | DR × DR|18| 2| 1|..|..|..|..|..|..|..|..| 0.19|
| 132 |804|3898| F2 |S × M | 0|3823| F1 | Do. | 0 | D × DR |19|..|..|..|..|..|..|..|..|..|..| 0.00|
| 133 |804|3902| F2 | Do. | 0|3823| F1 | Do. | 0 | Do. |33|..|..|..|..|..|..|..|..|..|..| 0.00|
| 134 |804|4657| F2 | Do. | 0|3823| F1 | Do. | 0 | Do. | 8|..|..|..|..|..|..|..|..|..|..| 0.00|
| 135 |804|4716| F2 | Do. | 0|3823| F1 | Do. | 0 | Do. |19|..|..|..|..|..|..|..|..|..|..| 0.00|
| 136 |804|5431| F2 | Do. | 0|3823| F1 | Do. | 0 | Do. |16|..|..|..|..|..|..|..|..|..|..| 0.00|
+------+---+----+-----+---------+---+----+-----+--------+---+--------+--+--+--+--+--+--+--+--+--+--+--+-----+
In table 38 I have given in the section lying between that headed
"Father" and that headed "Offspring" the "Matings." This column
differs from the others of the table in not being, in general,
based upon observation, but upon a sometimes complicated judgment.
Of course, all of the F1 generation, where this generation occurs,
may be taken as of DR composition; but the decision as to whether
a given individual of F2 is a DR, an extracted dominant, or an
extracted recessive is not always easy, because of the manifestation
of imperfect dominance. But the assignments are by no means
arbitrary. Taking the Brahma crosses, which are by far the most
numerous, we see, from tables 31, B and 33, that those F2 individuals
that have a boot of grade 6 or higher are almost certainly extracted
recessives (which are equivalent to pure-bred Dark Brahmas). Those
with a grade of 3 or even 4 and lower to 2 or even 1 are probably
heterozygotes, while those with grade 0 and some of those with grade
1 are extracted dominants. In cases of doubt the distribution of
grades in the offspring will give the deciding vote. In case the
individual has been used as a parent in more than one mating the
results in all the matings are taken into account, for the germinal
constitution of an individual must be regarded as fixed at all times
and in all matings. The assignment under "Matings" has, then, been
made by the application of the above rules.
In tables 39 to 43 there are grouped together the progeny from
matings of the same sort, selecting from table 38 the crosses into
which the Dark Brahma enters as the booted parent.
TABLE 39.--_RR × RR crosses from table 38._
+-------+-----------------------------------------------------+----------------------+
| | Boot-grade in offspring. | Parental grades. |
|Serial +--+---+---+---+---+----+----+---+----+----+----+-----+-------+-----+--------+
| No. | 0| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Avge.|Female.|Male.|Average.|
+-------+--+---+---+---+---+----+----+---+----+----+----+-----+-------+-----+--------+
| 1 |..| ..| ..| ..| ..| ..| ..| ..| ..| 10| 15| 9.6| 7 | 9 | 8.0 |
| 2 |..| ..| ..| ..| ..| ..| ..| ..| ..| 1| 1| 9.5| 4 | 8 | 6.0 |
| 3 |..| ..| ..| ..| ..| ..| ..| ..| 1| 3| 4| 9.4| 5 | 9 | 7.0 |
| 4 |..| ..| ..| ..| ..| ..| ..| ..| 1| 1| 2| 9.3| 6 | 7 | 6.5 |
| 5 |..| ..| ..| ..| ..| 1| ..| ..| 3| 4| 9| 9.1| 9 | 9 | 9.0 |
| 6 |..| ..| ..| ..| ..| 1| 1| 1| ..| 2| 7| 8.8| 8 | 9 | 8.5 |
| 7 |..| ..| ..| ..| ..| ..| 1| 1| 1| 1| 4| 8.8| 2 | 9 | 5.5 |
| 8 |..| ..| ..| ..| ..| ..| 1| 1| 2| 2| 3| 8.6| 7 | 5 | 6.0 |
| 9 |..| ..| ..| ..| 1| ..| ..| 1| 4| 2| 3| 8.3| 7 | 5 | 6.0 |
| 10 |..| ..| ..| ..| ..| ..| 1| 2| 4| 3| ..| 7.9| 8 | 6 | 7.0 |
| 11 |..| ..| ..| ..| 1| 1| ..| 3| ..| 6| 1| 7.8| 5 | 5 | 5.0 |
| 13 |..| ..| ..| ..| ..| 1| 1| 2| 1| 1| 1| 7.4| 6 | 7 | 6.5 |
| 18 |..| ..| ..| ..| 1| ..| 2| ..| 2| ..| 1| 7.0| 10 | 9 | 9.5 |
| 21 |..| ..| ..| ..| 3| 7| 7| 7| 7| 5| 2| 6.8| 9 | 6 | 7.5 |
| 25 |..| ..| ..| ..| ..| 2| 1| ..| ..| ..| 1| 6.5| 7 | 7 | 7.0 |
| 37 |..| ..| ..| 2| 8| 5| 6| 2| 8| 3| ..| 6.0| 8 | 6 | 7.0 |
| 39 |..| ..| ..| 5| 4| 6| 6| 1| 11| 1| ..| 5.9| 8 | 8 | 8.0 |
| 41 |..| ..| 1| 2| 1| 8| 2| 3| 6| ..| ..| 5.8| 9 | 7 | 8.0 |
| 49 |..| 1| 1| 1| 2| 3| ..| 2| 2| 1| ..| 5.2| 10 | 7 | 8.5 |
| 55 |..| ..| ..| 2| 1| 4| 1| 2| ..| ..| ..| 5.0| 6 | 7 | 6.5 |
| +--+---+---+---+---+----+----+---+----+----+----+-----+ | | |
|Totals | | | | | | | | | | | | | | | |
| (287)|..| 1| 2| 12| 22| 39| 30| 28| 53| 46| 54| 7.25| | | |
|Per | | | | | | | | | | | | | | | |
| cent.|..|0.3|0.7|4.2|7.7|13.6|10.5|9.8|18.5|16.0|18.8| ...| | | |
+-------+--+---+---+---+---+----+----+---+----+----+----+-----+-------+-----+--------+
TABLE 40.--_DR × RR crosses from table 38._
+-----------+-------------------------------------------------------------+
| | Boot-grade in offspring. |
| Serial +---+---+---+----+----+-----+----+----+----+----+----+--------+
| No. | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Average.|
+-----------+---+---+---+----+----+-----+----+----+----+----+----+--------+
| 14 | ..| 2| 1| ..| 1| 3 | ..| 1 | 3 | 6 | 5 | 7.2 |
| 15 | ..| ..| ..| ..| 3| 2 | 3| 1 | 1 | 1 | 5 | 7.1 |
| 16 | ..| ..| ..| 1| 4| 1 | 2| 7 | 6 | 1 | .. | 7.1 |
| 17 | ..| ..| ..| ..| 1| .. | ..| 1 | .. | .. | 1 | 7.0 |
| 20 | ..| ..| ..| 1| 1| 2 | 2| .. | 1 | 1 | 3 | 6.9 |
| 22 | ..| ..| ..| 2| 1| .. | 1| .. | .. | 2 | 2 | 6.8 |
| 23 | ..| ..| ..| 2| 2| 2 | 1| .. | .. | 3 | 3 | 6.7 |
| 24 | ..| ..| ..| ..| 1| .. | ..| 1 | .. | 1 | .. | 6.7 |
| 26 | 1| ..| ..| 1| 4| 6 | 9| 4 | 4 | 6 | 3 | 6.5 |
| 27 | ..| ..| ..| 2| 3| .. | 3| 1 | 1 | 4 | 1 | 6.5 |
| 28 | ..| ..| 1| 2| 6| 13 | 11| 5 | 11 | 8 | 3 | 6.3 |
| 29 | ..| ..| ..| 2| 2| 5 | 2| 1 | 1 | 3 | 2 | 6.3 |
| 30 | ..| ..| ..| 1| 3| 8 | 5| 2 | .. | 2 | 4 | 6.3 |
| 31 | ..| ..| ..| 6| 4| 1 | ..| 1 | 1 | 1 | 6 | 6.2 |
| 32 | ..| ..| ..| 1| 5| 4 | 3| 1 | 2 | 2 | 2 | 6.1 |
| 33 | ..| ..| ..| 5| 6| 11 | 12| 7 | 4 | 9 | .. | 6.1 |
| 34 | ..| ..| 1| ..| ..| .. | 1| .. | 2 | .. | .. | 6.0 |
| 35 | ..| ..| 1| ..| ..| 1 | 3| .. | 1 | 1 | .. | 6.0 |
| 36 | ..| ..| 2| 3| 3| .. | 2| .. | .. | 5 | 2 | 6.0 |
| 40 | ..| 1| 2| 3| 2| 5 | 3| 5 | 9 | 1 | .. | 5.8 |
| 42 | ..| ..| 1| 3| 9| 5 | 8| 4 | 7 | 2 | .. | 5.7 |
| 43 | ..| ..| ..| ..| 7| 4 | 3| 2 | 3 | 1 | .. | 5.7 |
| 44 | ..| ..| ..| 1| ..| 1 | ..| .. | .. | 1 | .. | 5.7 |
| 45 | ..| ..| 1| 2| 5| 3 | 1| 1 | 1 | 4 | .. | 5.6 |
| 46 | ..| ..| 3| 5| 2| 7 | 5| 6 | 2 | 4 | .. | 5.5 |
| 47 | ..| 2| 2| 3| 8| 9 | 5| 3 | 7 | 6 | .. | 5.5 |
| 48 | ..| ..| ..| 1| 4| 2 | 1| .. | 1 | .. | 1 | 5.3 |
| 51 | ..| ..| ..| ..| 3| 2 | 1| .. | 1 | .. | .. | 5.1 |
| 52 | 1| 1| 1| 4| 1| 7 | 2| 2 | 2 | .. | 2 | 5.0 |
| 53 | 1| 1| ..| 1| 2| .. | 1| .. | 1 | 1 | 1 | 5.0 |
| 54 | ..| ..| ..| 1| 2| 1 | 1| .. | 1 | .. | .. | 5.0 |
| 59 | ..| ..| 2| 1| 2| 2 | 1| .. | 1 | .. | .. | 4.9 |
| 60 | ..| ..| 2| 19| 8| 13 | 6| 4 | 5 | 2 | 1 | 4.8 |
| 61 | ..| 1| 1| 1| 1| .. | 1| .. | 1 | 1 | .. | 4.8 |
| 62 | ..| ..| 1| 3| 4| 1 | 1| 2 | .. | 1 | .. | 4.7 |
| 63 | 1| 1| 2| 8| 6| 1 | 2| 2 | 4 | 2 | .. | 4.6 |
| 66 | ..| ..| ..| 4| 7| 2 | 2| 2 | .. | .. | .. | 4.5 |
| 70 | ..| ..| 2| 2| 3| 2 | 2| 1 | .. | .. | .. | 4.3 |
| 72 | ..| ..| 1| 9| 6| 6 | 4| 1 | .. | .. | .. | 4.2 |
| 73 | ..| ..| 1| ..| 2| 1 | 1| .. | .. | .. | .. | 4.2 |
| 77 | 7| 4| 6| 5| 7| 5 | 9| 3 | 6 | 1 | .. | 4.1 |
| 78 | 1| 3| 13| 13| 8| 6 | 7| 6 | 3 | .. | .. | 4.1 |
| 80 | ..| 1| 6| 8| 2| 6 | ..| 3 | 1 | .. | .. | 4.0 |
| 82 | 2| 1| 4| 4| 3| 2 | 4| .. | 1 | 1 | .. | 3.8 |
| 83 | 1| 4| 2| 4| 3| 2 | 1| .. | .. | .. | .. | 3.8 |
| 84 | 6| 5| 23| 10| 5| 3 | 4| 5 | 8 | 3 | 1 | 3.8 |
| 86 | 1| ..| 8| 6| 9| 3 | 2| .. | 2 | .. | .. | 3.7 |
| 89 | 1| ..| 4| 2| 4| 1 | 1| 1 | .. | .. | .. | 3.4 |
| 90 | ..| ..| 6| 7| 7| 3 | 1| .. | .. | .. | .. | 3.4 |
| 97 | 1| 1| 7| 6| 6| 4 | 1| .. | .. | .. | .. | 3.2 |
| 98 | 3| 4| 10| 16| 12| 4 | 1| 2 | .. | .. | .. | 3.1 |
| +---+---+---+----+----+-----+----+----+----+----+----+--------+
|Total(1199)| 27| 32|117| 181| 200| 172 | 142| 88 |105 | 87 | 48 | 5.04 |
|Per cent. |2.3|2.7|9.8|15.1|16.7|14.3 |11.9|7.3 |8.8 |7.2 |4.0 | ... |
+-----------+---+---+---+----+----+-----+----+----+----+----+----+--------+
TABLE 41.--_DR × DD crosses._
+---------+------------------------------------------------+
| | Boot-grade in offspring. |
| Serial +------+------+------+------+-----+-----+--------+
| No. | 0 | 1 | 2 | 3 | 4 | 5 |Average.|
+---------+------+------+------+------+-----+-----+--------+
| 101 | 3 | 3 | 2 | 6 | 4 | 2 | 2.9 |
| 113 | 6 | 7 | 3 | 5 | 1 | ... | 1.5 |
| 116 | 9 | 3 | 5 | 3 | ... | ... | 1.1 |
| +------+------+------+------+-----+-----+--------+
|Total(62)| 18 | 13 | 10 | 14 | 5 | 2 | 1.69 |
|Per cent.| 29.5 | 21.3 | 16.4 | 23.0 | 8.2 | 1.6 | ... |
+---------+------+------+------+------+-----+-----+--------+
TABLE 42.--_DR x DR crosses._
+-----------+---------------------------------------------------------+
| | Boot-grade in offspring. |
|Serial No. +----+---+----+----+----+----+---+---+---+---+---+--------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10|Average.|
+-----------+----+---+----+----+----+----+---+---+---+---+---+--------+
| 19 | ..| ..| ..| ..| 1| 1| ..| ..| ..| 1| ..| 7.0 |
| 54 | ..| ..| ..| 2| 1| 6| 4| 2| ..| ..| ..| 5.2 |
| 56 | ..| ..| ..| 2| 5| 2| ..| 3| 1| ..| ..| 5.0 |
| 57 | ..| 2| 3| 3| 2| 4| 1| 1| 1| 2| 2| 5.0 |
| 58 | 1| 2| 1| 4| 1| ..| ..| ..| 8| ..| ..| 4.9 |
| 59 | ..| ..| 2| 1| 2| 2| 1| ..| 1| ..| ..| 4.9 |
| 64 | ..| ..| ..| ..| 4| 2| 1| ..| ..| ..| ..| 4.6 |
| 65 | 1| ..| 3| 6| 1| 4| 2| 7| ..| ..| ..| 4.5 |
| 67 | 4| 1| 4| ..| ..| 4| 2| ..| 2| 1| 2| 4.3 |
| 68 | 3| 2| 6| 5| 6| 6| 3| ..| 2| 4| 1| 4.3 |
| 69 | 9| 3| 1| 6| 8| 2| 6| 6| 3| 1| 3| 4.3 |
| 71 | ..| ..| 2| 2| 3| 2| 2| 1| ..| ..| ..| 4.3 |
| 75 | ..| 2| 5| 11| 7| 10| 5| ..| 2| 1| ..| 4.1 |
| 76 | 3| 2| 1| 9| 5| 5| 2| 2| 3| 1| ..| 4.1 |
| 79 | 6| 1| 3| 9| 5| 4| 5| 1| 4| 1| 1| 4.1 |
| 81 | 2| 3| 3| 9| 3| 5| 8| 2| ..| 1| ..| 4.0 |
| 85 | 7| 3| 5| 3| 7| 7| 2| 6| 1| 1| ..| 3.7 |
| 88 | 1| ..| 2| 1| 3| 4| ..| ..| ..| ..| ..| 3.6 |
| 91 | 2| 1| 1| 8| 11| 2| 1| ..| ..| ..| ..| 3.4 |
| 92 | 11| 1| 2| 8| 5| 3| 1| ..| 2| 2| 2| 3.4 |
| 93 | 2| 3| 4| 6| 4| 1| 6| ..| ..| ..| ..| 3.3 |
| 94 | 8| 2| 1| 8| 1| ..| ..| 1| 2| 3| ..| 3.3 |
| 95 | 3| ..| 7| 9| 5| 2| ..| ..| ..| ..| ..| 3.3 |
| 96 | 1| 4| 6| 12| 8| 4| ..| 2| ..| ..| ..| 3.2 |
| 99 | 1| 5| 10| 17| 10| 4| 1| ..| ..| ..| ..| 3.0 |
| 100 | 1| 2| 2| 3| ..| 2| ..| 1| ..| ..| ..| 2.9 |
| 102 | 2| 4| 3| 8| 3| 2| 2| ..| ..| ..| ..| 2.8 |
| 103 | 1| 2| ..| ..| 1| 1| 1| ..| ..| ..| ..| 2.8 |
| 104 | 7| 6| 9| 8| 7| 2| 1| 2| ..| 1| ..| 2.7 |
| 105 | 7| 3| 5| 6| 2| 9| ..| ..| ..| ..| ..| 2.6 |
| 106 | 5| 1| 4| 2| 2| 2| 1| ..| ..| ..| ..| 2.3 |
| 107 | 9| 3| 6| 5| 1| 2| 4| ..| ..| ..| ..| 2.3 |
| 109 | 6| 2| 5| 5| 2| 2| ..| ..| ..| ..| ..| 2.1 |
| 110 | 2| 1| 2| ..| 1| 1| ..| ..| ..| ..| ..| 2.0 |
| +----+---+----+----+----+----+---+---+---+---+---+--------+
|Total (851)| 105| 61| 108| 178| 127| 109| 62| 37| 32| 20| 12| 3.59 |
|Per cent. |12.3|7.2|12.7|20.9|14.9|12.8|7.3|4.4|3.8|2.3|1.4| ... |
+-----------+----+---+----+----+----+----+---+---+---+---+---+--------+
TABLE 43.--_DD x DD (Silkie crosses)._
+-----------+----------------------------+
| | Boot-grade in offspring. |
|Serial No. +----+----+----+----+--------+
| | 0 | 1 | 2 | 3 |Average.|
+-----------+----+----+----+----+--------+
| 117 | 2| ..| ..| 1| 1.00 |
| 118 | ..| 1| ..| ..| 1.00 |
| 128 | 26| 6| 1| 1| 0.32 |
| 130 | 11| 4| ..| ..| 0.27 |
| 131 | 18| 2| 1| ..| 0.19 |
| 132 | 19| ..| ..| ..| 0.0 |
| 133 | 33| ..| ..| ..| 0.0 |
| 134 | 8| ..| ..| ..| 0.0 |
| 135 | 19| ..| ..| ..| 0.0 |
| 136 | 16| ..| ..| ..| 0.0 |
| +----+----+----+----+--------+
|Total (169)| 152| 13| 2| 2| 0.14 |
|Per cent. |89.9| 7.7| 1.2| 1.2| .... |
+-----------+----+----+----+----+--------+
The significance of the data given in tables 39 to 43 is best brought
out by summarizing them. Especially instructive is a comparison of
the pure-bred with the hybrids. Since the data are most complete in
the case of the Brahma crosses, these will be considered in most
detail. So far as they go, the results with the Cochins and Silkies
are entirely confirmatory.
Table 44 shows clearly, first, that there are families of two booted
parents that never fail to produce booted offspring. There is,
however, even in pure-bred booted races, a marked variability in the
grade of booting, extending from 3 (or 4) to 10. The significance of
this variability must be left for future investigations. There is in
the least boot, as it were, an extension of the field of activity of
the feather-inhibiting factor that is always present on the hinder
aspect of the shank, so that it interferes with the development of
feathers on the inner face of the shank also.
In the first hybrid generation all somatic cells are hybrid. The
feather inhibitor is present in the skin of the shank, but its
strength is diluted by the presence in the same cells of a protoplasm
devoid of the inhibiting property. Consequently, the prevailing
grade of the boot falls from 6 (or 10) to 3. Despite the dilution,
inhibition is complete in about 8 per cent of the offspring (grade
0); in about 10 per cent of the offspring the inhibiting factor is
so weak that the boot develops as in the pure-blooded Brahma. When,
as a result of inbreeding F1's, the feather-inhibiting factor is
eliminated from certain offspring, and such full-feathered birds are
bred together, we find a return of the mode to high numbers, such as
8 to 10 (but also 5). There is no doubt of segregation.
TABLE 44.--_Brahma crosses. (All entries are percentages.)_
+---------------+------+----------------------------------------------------------------------------+
| | | Boot-grade in offspring. |
| Percentage. | From +------+------+-----+-----+-----+-----+-----+-----+-----+-----+-----+--------+
| |table.| | | | | | | | | | | |Average |
| | | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | grade. |
+---------------+------+------+------+-----+-----+-----+-----+-----+-----+-----+-----+-----+--------+
|Pure blood | 31, B| .... | .... | ....| 3.3| 3.3| 6.6| 24.6| 4.9| 9.8| 14.8| 32.8| 7.62 |
|F1 (D × R) | 32 | 7.9 | 13.8 | 16.8| 31.0| 17.5| 7.8| 3.4| 1.1| 0.7| ....| ....| 2.84 |
|Extracted R × R| 39 | .... | 0.3 | 0.7| 4.2| 7.7| 13.6| 10.5| 9.8| 18.5| 16.0| 18.8| 7.25 |
|DR × RR | 40 | 2.3 | 2.7 | 9.8| 15.1| 16.7| 14.3| 11.9| 7.3| 8.8| 7.2| 4.0| 5.04 |
| | |\---------------\/---------------/ \--------------\/-------------/| |
| | | 50 p. ct. DR. 50 p. ct. RR. | |
|DR × DR | 42 | 12.3 | 7.2 | 12.7| 20.9| 14.9| 12.8| 7.3| 4.4| 3.8| 2.3| 1.4| 3.59 |
| | |\------\/------/ \------\/------/ \--------------\/-------------/| |
| | | 25 p. ct. DD. 50 p. ct. DR. 25 p. ct. RR. | |
|DR × DD | 41 | 29.5 | 21.3 | 16.4| 23.0| 8.2| 1.6| ....| ....| ....| ....| ....| 1.69 |
| | |\-----\/----/|\----------\/---------/| | | | | | |
| | |50 p. ct. DD.| 50 p. ct. DR. | | | | | | |
+---------------+------+-------------+-----------------------+-----+-----+-----+-----+-----+--------+
If a heterozygous bird be mated to a recessive the variability
of the offspring is much increased, owing to the occurrence in
the progeny of both DR and RR individuals (table 40). The
offspring do not, to be sure, fall into two distinct and well-defined
types, as in typical Mendelian cases; but one part of the range of
variation agrees fairly with that of pure RR's, _i. e._, Brahmas,
and the remainder with that of heterozygotes. And if we make the
division in the middle of the middle class, viz, 5, we shall find
a close approximation to that equality of extracted recessives and
heterozygotes that the segregation theory calls for (table 44).
If, again, two heterozygous birds be mated, the variability is still
greater and the proportion of clean-footed offspring rises to 12 per
cent. These, together with some of the extremely slightly booted
offspring, represent the extracted dominants. The whole range now
falls into three regions divided by the middle of grades 2 and 5.
These regions correspond to the DD's, the DR's, and the RR's
of typical cases of segregation, and their relative proportions are
approximately as 25: 50: 25.
Finally, if a heterozygote be mated to an extracted dominant the
proportion of clean-footed offspring rises to about 30 per cent and
the whole range of variation falls readily into two parts, the one
comprising grades 0 and 1, the other grades 2 and above. The first
includes the DD offspring; the second, the DR's; and their
frequency is equal. One will not fail to note that we are not here
dealing with a case of blending simply, and the inheritance of the
blend; such a view is negatived by the fact of the much greater
variability of DR × DR cross over the simple D × R cross of
the first generation. One may safely conclude, then, that, despite
the apparent blending of booting characters in the first generation
of hybrids, true segregation takes place. But this is always to be
seen through the veil of imperfect dominance.
A casual examination of table 38 would seem to show a correlation
between the grade of booting of the parents and that of the average
of their progeny. Thus, on the whole, the parental grades run high
in the upper part of the table and run low in the lower part.
This relation would thus seem to confirm Castle's conclusion for
polydactylism in guinea-pigs that there is an inheritance of the
degree of a character. One consequence of such an inheritance would
be that it would be possible in a few generations to increase or
diminish the grade of a character and fix any required grade in the
germ-plasm. A more careful consideration of the facts of the case
shows that this relation has another interpretation. The grade of
boot of the different parents varies largely because their gametic
constitution is diverse. As table 39 shows, the parents of the upper
part of table 38 are chiefly extracted recessives, and consequently
their booting and that of their offspring are characterized by high
grades. On the other hand, the parents of the lower part of the table
are heterozygous or extracted dominants and, consequently, their
grades and also those of their offspring average low. On account of
the lack of homogeneity of the families in table 38, one can draw
from it no proper conclusions as to relation between parental and
filial grades. On the other hand, from a homogeneous table, like
table 39, we can hope to reach a conclusion as to the existence of
such a relation. I have calculated, in the usual biometric fashion,
the coefficient of correlation between average parental and filial
grades, and found it to be -0.17 ± 0.13. This can only be interpreted
to mean that in a homogeneous assemblage of families there is no
correlation between the grade of booting of parents and offspring.