CHAPTER VII._Inheritance of Characteristics in Domestic Fowl

NOSTRIL-FORM.

In my 1906 report I described in detail the form of the nostril in

poultry. Usually it is closed down to a narrow slit, but in some

races, as, _e. g._, the Polish and Houdans, the closing flap of

skin fails to develop and the nostril remains wide open. This is

apparently an embryonic condition. Thus in Keibel and Abraham's

(1900) Normaltafeln of the fowl it is stated that the outer nasal

opening, which is at first wide open, becomes closed with epithelium

at about the middle of the sixth day of development. The Polish and

Houdan fowl thus retain in the outer nasal opening an embryonic

condition. The question is: How does this embryonic, open condition

of the nostril behave in heredity with reference to the more advanced

narrow-slit condition?

The wide-nostriled races used were both the Polish and the Houdan.

The condition of the external nares is much the same in the two,

but is slightly more exaggerated in the Houdans than in the Polish.

The open nostril is often associated with a fold across the

culmen, apparently due to the upturning of the anterior end of the

premaxillary process of the nasal bone. Breeders of Houdans have

sought to exaggerate the height of the fold. In both races there

is great variability in the degree of "openness" of the nostril,

and to indicate this I have adopted a scale of 10 grades (running

from 1, the narrowest, to 10, the widest). To get some idea of this

variability let us consider the grade of nostril in some families of

pure Houdans.

TABLE 45.--_Variability (expressed in decimal grades) of the

degree of "openness" of the nostrils in families of "pure-bred"

Houdans._

+------+---+-----------+-----------+--------------------------------------+

|Serial|Pen| | | |

| No. |No.+----+------+----+------+--+--+--+--+---+---+---+----+----+----+

| | | No.|Grade.| No.|Grade.| 1| 2| 3| 4| 5 | 6 | 7 | 8 | 9 | 10 |

+------+---+----+------+----+------+--+--+--+--+---+---+---+----+----+----+

| 1 |727|2457| 9 | 831| 10 |..|..|..|..| ..| ..| ..| .. | 5 | 4 |

| 2 |727|2459| 10 | 831| 10 |..|..| 1|..| ..| ..| 1| 3 | 7 | 3 |

| 3 |727|2494| 9 | 831| 10 |..|..|..|..| ..| ..| ..| .. | 1 | 4 |

| 4 |727|3105| 9 | 831| 10 |..| 1|..| 1| 2| 1| ..| 5 | 7 | 3 |

| 5 |727|3106| 9 | 831| 10 |..|..|..|..| ..| ..| ..| .. | 2 | 1 |

| 6 |803|2457| 8 |7522| 9 |..| 1| 1|..| ..| 2| 4| 7 | 10 | 3 |

| 7 |803|2459| 10 |7522| 9 |..|..|..|..| ..| ..| 1| 6 | 4 | 2 |

| 8 |803|3105| 9 |7522| 9 | 1|..|..|..| 4| 2| 2| 7 | 3 | 7 |

| | +--+--+--+--+---+---+---+----+----+----+

| | Totals (119) | 1| 2| 2| 1| 6| 5| 8| 28 | 39 | 27 |

| | |\----\/---/| | | | | | |

| | Percentages | 5.3 |5.3|4.4|7.1|24.8|34.5|23.9|

+------+---------------------------+-----------+---+---+---+----+----+----+

Table 45 shows that the prevailing grade in the offspring of pure

Houdans is 9; that grades 8 and 10 are also extremely common; and

that lower grades, even down to 1, may occur, but these are much less

common.

We have next to consider the grade-distribution of the offspring of

the narrow mated with the wide nostril.

TABLE 46.--_Distribution of the frequency of the different grades

of "openness" of nostril when one parent has the open nostril and

the other the closed._

+--------+---+--------------------------+--------------------------+-----------------------------------------+

| Serial |Pen+---+-----+------------+---+----+-----+-----------+---+----+----+----+----+---+---+---+---+--+--+

| No. |No.|No.| Gen.| Races. |Gr.| No.| Gen.| Races. |Gr.| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9|10|

+--------+---+---+-----+------------+---+----+-----+-----------+---+----+----+----+----+---+---+---+---+--+--+

| 9 |727|121| P. |Dk. Brahma. | 1 | 831| P. |Houdan | 10| 9 | 11 | 6 | 6 | 2| 3| 1| 1|..|..|

| 10 |735|142| P. |Mediterran. | 1 | 30| P. |Polish | 8| 4 | 1 | .. | .. | ..| ..| ..| ..|..|..|

| 11 |735|177| P. | Do. | 1 | 30| P. | Do. | 8| .. | 4 | 2 | 1 | ..| ..| ..| ..|..|..|

| 12 |735|198| P. | Do. | 1 | 30| P. | Do. | 8| .. | 3 | 1 | .. | ..| 1| ..| ..|..|..|

| | | | | | +----+----+----+----+---+---+---+---+--+--+

| | | | | Totals (56) | ..| 13 | 19 | 9 | 7 | 2| 4| 1| 1|..|..|

| | | | | Percentages | ..|23.2|34.0|16.1|12.5|3.6|7.1|1.8|1.8|..|..|

| | | | | | +====+====+====+====+===+===+===+===+==+==+

|[A]12_a_|813|912| F2 |Houd × Legh.| 2 |3904| F3 |Houd × Legh.| 7| 3 | 10 | 3 | 1 | 1| ..| ..| ..|..|..|

+--------+---+---+-----+------------+---+----+----+------------+---+----+----+----+----+---+---+---+---+--+--+

[A]: Extracted D × R.

Table 46 gives us a picture of the nature of the dominance in this

case. At first sight the narrow nostril, grades 1 and 2, including

57 per cent of the offspring, appears to be dominant. But, as later

evidence shows, it is recessive. The wide nostril is dominant, but so

imperfectly that only 10 per cent have a nostril above one-half open.

Let us now consider the distribution of nostril form in families

whose parents are hybrids of the first or later generation, crossed

respectively on recessives, heterozygotes, and dominants (tables

47-49).

TABLE 47.--_Distribution of frequency of the different grades of

"openness" of nostril when one parent is heterozygous and the

other recessive, i. e., with closed nostril (DR × R)._

+------+---+----------------------------+-------------------+-----+--------------------------------------+

|Serial|Pen+---+-----+--------------+---+----+----+-----+---+Total+----+----+----+---+---+--+---+--+--+--+

| No. |No.| | | | | | | | | gr. | | | | | | | | | | |

| | |No.| Gen.| Races. |Gr.| No.|Gen.|Race.|Gr.| | 1 | 2 | 3 | 4 | 5 | 6| 7| 8| 9|10|

+------+---+---+-----+--------------+---+----+----+-----+---+-----+----+----+----+---+---+--+---+--+--+--+

| 13 |768|298| F2 |Med. × Polish.| 2 |1689| P. |Med | 1 | 3 | 11 | 9 | 3 | 1 | 3 |..| 1|..|..|..|

| 14 |768|509| F1 | Do. | 1 |1689| P. | Do. | 1 | 2 | 12 | 5 | 6 | 1 | 1 | .| ..|..|..|..|

| | | | | +----+----+----+---+---+--+---+--+--+--+

| | | | | Totals (53) | 23 | 14 | 9 | 2 | 4 | 0| 1 |..|..|..|

| | | | | Percentages |43.4|26.4|17.0|3.8|7.6|..|1.9|..|..|..|

+------+---+---+-----+--------------------------------------------+----+----+----+---+---+--+---+--+--+--+

The study of the tables 45 to 54 establishes the following

conclusions:

First, high nostril is dominant. This means that there is a factor

that inhibits the development of the narial flap. In the absence of

such a factor the flap goes on developing normally. This hypothesis

is opposed to the conclusion that I reached in my report of 1906 (pp.

68, 69). I there said:

A close agreement exists between the percentage obtained in

each generation and the expectation of the Mendelian theory,

assuming that narrow nostril is dominant. The statistics do

not, however, tell the whole story. In 36 per cent of the

cases in the F1 generation the nostril was wider than in the

"narrow" ancestor. Even in the F2 generation nearly half of the

"narrow and intermediate" were of the intermediate sort. This

intermediate form is evidence that dominance is imperfect and

segregation is incomplete.

TABLE 48.--_Distribution of frequency of grades of "openness" in

offspring when both parents are heterozygous (DR × DR)._

+------+-----+----------------------------------+----------------------------+----+-------------------------------------------------------+

|Serial| Pen +------+-----+---------------+-----+------+-----+---------------+----+Total+----+----+----+----+----+----+----+----+----+----+

| No. | No. | | | | | | | | | gr. | | | | | | | | | | |

| | | No. | Gen.| Races. | Gr. | No. | Gen.| Races. | Gr.| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+-----+------+-----+---------------+-----+------+-----+---------------+----+-----+----+----+----+----+----+----+----+----+----+----+

| 15 | 802 | 5314 | F1 | Polish × Min | 3 | 6652 | F1 | Polish × Min | 4 | 7 | 1 | 5 | 5 | .. | .. | 1 | .. | .. | 3 | 1 |

| 16 | 805 | 5307 | F1 | Do. | 5 | 4799 | F1 | Do. | 2 | 7 | 7 | 7 | 13 | 3 | 7 | 1 | .. | 2 | 2 | 1 |

| 17 | 852 | 5104 | F1 | Hou. × Dk. Br | 3 | 5969 | F1 | Hou. × Dk. Br | 3 | 6 | 4 | 11 | 4 | 2 | 1 | 1 | 1 | .. | .. | .. |

| 18 | 805 | 4800 | F1 | Polish × Min | 3 | 4799 | F1 | Polish × Min | 2 | 5 | 10 | 13 | 9 | 1 | 2 | 8 | .. | 1 | 2 | .. |

| 19 | 805 | 5308 | F1 | Do. | 3 | 4799 | F1 | Do. | 2 | 5 | 3 | 7 | 3 | 2 | 1 | .. | .. | .. | .. | .. |

| 21 | 759 | 797 | F1 | Houd. × Min | 3 | 570 | F1 | Houd. × Min | 2 | 5 | 2 | 4 | 2 | 2 | .. | .. | .. | .. | .. | 2 |

| 22 | 759 | 797 | F1 | Do. | 3 | 352 | F1 | Do. | 1 | 4 | .. | 2 | 2 | .. | .. | .. | .. | .. | 1 | 1 |

| 23 | 805 | 4447 | F1 | Polish × Min. | 2 | 4799 | F1 | Polish × Min | 2 | 4 | 6 | 5 | 4 | .. | 2 | .. | 1 | 1 | 3 | .. |

| 24 | 805 | 4765 | F1 | Do. | 2 | 4799 | F1 | Do. | 2 | 4 | 5 | 12 | 4 | 2 | 1 | 1 | 2 | .. | 2 | .. |

| 25 | 805 | 4797 | F1 | Do. | 2 | 4799 | F1 | Do. | 2 | 4 | 4 | 2 | 6 | .. | .. | .. | .. | 1 | .. | .. |

| 26 | 805 | 5163 | F1 | Do. | 2 | 4799 | F1 | Do. | 2 | 4 | 7 | 17 | 13 | 4 | 1 | 2 | 2 | 2 | 1 | .. |

| 27 | 805 | 5304 | F1 | Do. | 2 | 4799 | F1 | Do. | 2 | 4 | 5 | 9 | 8 | .. | 1 | .. | .. | .. | .. | .. |

| 28 | 852 | 7070 | F1 | Hou. × Dk. Br | 1 | 5969 | F1 | Hou. × Dk. Br | 3 | 4 | 4 | 11 | 4 | 2 | 1 | 1 | 1 | .. | .. | .. |

| 29 | 759 | 529 | F1 | Houd. × Min | 2 | 570 | F1 | Houd. × Min | 2 | 4 | 2 | 3 | .. | .. | .. | .. | .. | .. | .. | 1 |

| 30 | 759 | 529 | F1 | Do. | 2 | 352 | F1 | Do. | 2 | 4 | 1 | 3 | .. | .. | .. | .. | .. | .. | .. | .. |

| 31 | 728 | 174 | F1 | Hou. × Wh. L | 1 | 258 | F1 | Hou. × Wh. L | 2 | 3 | 2 | 7 | 2 | 1 | 1 | 1 | 1 | .. | .. | .. |

| 32 | 805 | 4798 | F1 | Polish × Min | 1 | 4799 | F1 | Polish × Min | 2 | 3 | 7 | 10 | 3 | 2 | 1 | 2 | .. | 4 | 2 | .. |

| 33 | 805 | 5323 | F1 | Do. | 1 | 4799 | F1 | Do. | 2 | 3 | 17 | 7 | 2 | .. | .. | 1 | .. | 2 | 1 | .. |

| | | | | +----+----+----+---------+----+----+----+----+----+

| | | | | Totals (435) | 92 |147 | 88 | 21 | 22 | 19 | 10 | 13 | 17 | 6 |

| | | | | Percentages |21.2|33.8|20.2|4.8 |5.0 |4.4 |2.3 |3.0 |3.9 |1.4 |

| | | | | |\-----------------/|\---------------------------/|

| | | | | | 80.0 | 20.0 |

+------+-----+------+-----+-------------------------------------------------------------+-------------------+-----------------------------+

TABLE 49.--_Distribution of frequency of grades of "openness" in

offspring when both parents are heterozygous (DR × DR, F2 and

later generations)._

+------+-----+---------------------------------+--------------------------------+-----+-------------------------------------------------+

|Serial| Pen +------+----+---------------+-----+------+----+---------------+----+Total+----+----+----+----+----+----+----+----+----+----+

| No. | No. | | | | | | | | | gr. | | | | | | | | | | |

| | | No. |Gen.| Races. | Gr. | No. |Gen.| Races. | Gr.| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+-----+------+----+---------------+-----+------+----+---------------+----+-----+----+----+----+----+----+----+----+----+----+----+

| 34 | 763 | 3799 | F2 | Hou. × Wh. L. | 6 | 2247 | F2 | Hou. × Wh. L. | 2 | 8 | .. | 2 | 2 | 2 | 2 | .. | 1 | .. | .. | .. |

| 35 | 765 | 84 | F1 | Do. | 3 | 1794 | F2 | Do. | 5 | 8 | 1 | 6 | 8 | 1 | 4 | 1 | 1 | 2 | 6 | 3 |

| 36 | 765 | 984 | F2 | Do. | 3 | 1794 | F2 | Do. | 5 | 8 | 8 | 3 | 1 | 2 | 2 | 1 | 0 | 2 | 5 | .. |

| 37 | 802 | 4013 | F3 | Polish × Min. | 4 | 6652 | F1 | Polish × Min. | 4 | 8 | 6 | 12 | 9 | 6 | .. | .. | .. | 1 | 1 | 1 |

| 38 | 802 | 3954 | F3 | Do. | 3 | 6652 | F1 | Do. | 4 | 7 | 4 | 12 | 3 | 2 | 1 | .. | 2 | 6 | 9 | 1 |

| 39 | 802 | 4038 | F2 | Do. | 3 | 6652 | F1 | Do. | 4 | 7 | 3 | 8 | 4 | 3 | 2 | .. | 1 | 4 | 1 | 1 |

| 40 | 802 | 4164 | F3 | Do. | 3 | 6652 | F1 | Do. | 4 | 7 | 6 | 8 | 6 | 2 | 1 | 1 | .. | 2 | 2 | 2 |

| 41 | 812 | 84 | F1 | Hou. × Wh. L. | 3 | 4118 | F3 | Hou. × Wh. L. | 4 | 7 | .. | 1 | 5 | 2 | 2 | 1 | 1 | 1 | 1 | 2 |

| 42 | 812 | 913 | F2 | Do. | 3 | 4118 | F3 | Do. | 4 | 7 | 10 | 6 | 6 | 1 | .. | .. | .. | 3 | 2 | 5 |

| 43 | 812 | 4728 | F3 | Do. | 3 | 4118 | F3 | Do. | 4 | 7 | 8 | 5 | 5 | 1 | 5 | 2 | 2 | 2 | 9 | 2 |

| 44 | 812 | 5120 | F3 | Do. | 3 | 4118 | F3 | Do. | 4 | 7 | 1 | 2 | 2 | .. | 1 | .. | .. | .. | 1 | 2 |

| 45 | 812 | 5540 | F3 | Polish × Min. | 3 | 4118 | F3 | Do. | 4 | 7 | 2 | 5 | 6 | 1 | 1 | .. | .. | .. | .. | .. |

| 46 | 763 | 2250 | F3 | Hou. × Wh. L | 5 | 2247 | F2 | Do. | 2 | 7 | 4 | 10 | 2 | .. | .. | .. | .. | 1 | 0 | 2 |

| 47 | 812 | 4726 | F2 | Do. | 2 | 4118 | F3 | Polish × Min. | 4 | 6 | 4 | 6 | 3 | .. | 2 | 1 | .. | 2 | 1 | 3 |

| 48 | 812 | 4735 | F3 | Do. | 2 | 4118 | F3 | Do. | 4 | 6 | 2 | 1 | 1 | .. | .. | .. | .. | 2 | 1 | .. |

| 49 | 765 | 1790 | F3 | Do. | 1 | 1794 | F2 | Hou. × Wh. L. | 5 | 6 | 9 | 14 | 9 | 1 | 3 | 0 | 2 | 0 | 3 | .. |

| 50 | 802 | 4012 | F3 | Polish × Min. | 1 | 6652 | F1 | Polish × Min. | 4 | 5 | 5 | 13 | 11 | 3 | 2 | .. | 1 | 3 | 1 | .. |

| 51 | 825 | 2198 | F3 | Do. | 3 | 3852 | F3 | Do. | 2 | 5 | .. | .. | 1 | 3 | .. | .. | .. | .. | .. | 1 |

| 52 | 728 | 2271 | F2 | Hou. × Wh. L. | 3 | 258 | F1 | Hou. × Wh. L. | 2 | 5 | 4 | 3 | 1 | 7 | 2 | 1 | 3 | 1 | 1 | 2 |

| 53 | 763 | 2700 | F2 | Do. | 3 | 2247 | F2 | Do. | 2 | 5 | 1 | 2 | 3 | 3 | .. | 1 | .. | .. | 2 | .. |

| 54 | 825 | 350 | F1 | Polish × Min. | 2 | 3852 | F3 | Polish × Min. | 2 | 4 | 4 | 13 | 6 | 4 | .. | .. | .. | 3 | 1 | 3 |

| 55 | 825 | 4708 | F3 | Do. | 2 | 3852 | F3 | Do. | 2 | 4 | 4 | 13 | 7 | 3 | .. | 1 | 1 | 1 | 2 | 3 |

| 56 | 825 | 5019 | F2 | Do. | 2 | 3852 | F3 | Do. | 2 | 4 | 1 | 1 | .. | .. | .. | .. | .. | 1 | 2 | 2 |

| 57 | 825 | 5035 | F3 | Do. | 2 | 3852 | F3 | Do. | 2 | 4 | 4 | .. | 3 | 1 | 1 | .. | .. | 1 | 1 | 1 |

| 58 | 825 | 5672 | F3 | Do. | 2 | 3852 | F3 | Do. | 2 | 4 | 1 | 3 | 2 | .. | 2 | .. | .. | 1 | 2 | 1 |

| 59 | 728 | 2248 | F2 | Hou. × Wh. L. | 2 | 258 | F1 | Hou. × Wh. L. | 2 | 4 | 3 | 6 | 7 | 2 | .. | .. | 1 | 0 | 1 | 3 |

| 61 | 763 | 377 | F1 | Do. | 1 | 2247 | F2 | Do. | 2 | 3 | 20 | 9 | 14 | 3 | 6 | 0 | 2 | 0 | 2 | 1 |

| | | | | +----+----+----+----+----+----+----+----+----+----+

| | | | | Totals (663) |115 |641 | 127| 53 | 39 | 10 | 8 | 39 | 57 | 41 |

| | | | | Percentages |17.4|24.7|19.2| 8.0|5.9 |1.5 |2.7 |5.9 |8.6 |6.2 |

| | | | | |\-----------------/|\---------------------------/|

| | | | | | 69.3 30.7 |

+------+-----+------+----+------------------------------------------------------------+-------------------+-----------------------------+

These earlier data were not even roughly quantitative, and it is the

quantitative data that first give the key to the true relations.

However, sufficient evidence for the change in the conclusion is

certainly due. The evidence is found in a careful study of table

55, keeping constantly in mind this fundamental principle that the

recessive condition alone in the parents can never give rise to

the dominant; for the recessive condition implies entire absence

of the dominant factor. But the pure dominant condition will vary

in the direction of the recessive condition; such a result implies

only a partial failure of the factor to develop completely; and we

should not be surprised if occasionally the failure were complete.

This implies no "reversal of dominance," but rather an arrested

development of the factor.

TABLE 50.--_Distribution of frequency of grades of "openness" in

offspring when one parent is heterozygous and the other an

original dominant (DR × D, originals)._

+------+----+---------------------------------+---------------------+-----+-------------------------------------------------+

| No. | No.+-----+----+------------------+---+-----+----+------+---+ gr. |----+----+----+----+----+----+----+----+----+----+

| | | No. |Gen.| Races. |Gr.| No. |Gen.|Races.|Gr.| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+----+-----+----+------------------+---+-----+----+------+---+-----+----+----+----+----+----+----+----+----+----+----+

| 62 | 803| 529| F1 | Houd. × Min. | 3 | 7522| P. | Houd.| 9 | 12 | 4 | 2 | 4 | 1 | 2 | .. | .. | 2 | 2 | 1 |

| 63 | 803| 7065| F1 | Houd. × Dk. Brah.| 1 | 7522| P. | Do. | 9 | 10 | 6 | 11 | 6 | 4 | 2 | 1 | 2 | 6 | 4 | 1 |

| | | | | +----+----+----+----+----+----+----+----+----+----+

| | | | | Totals (61) | 10 | 13 | 10 | 5 | 4 | 1 | 2 | 8 | 6 | 2 |

| | | | | Percentages |16.4|21.3|16.4| 8.2| 6.5| 1.6| 3.3|13.1| 9.8| 3.3|

| | | | | |\--------\/-------/|\-------------\/------------/|

| | | | | | 62.3 | 37.7 |

+------+----+-----+----+--------------------------------------------------+-------------------+-----------------------------+

TABLE 51.--_Distribution of frequency of grades of "openness" in

offspring when one parent is heterozygous and the other an

extracted dominant (DR × DD, extracted)._

[ABBREVIATIONS: H = Houdan; L = Leghorn; M = Minorca; P = Polish; WL = White Leghorn.]

+------+----+------------------------+----------------------+-----+-------------------------------------------------+

| No. | No.+-----+----+---------+---+-----+----+-------+---+ gr. +----+----+----+----+----+----+----+----+----+----+

| | | No. |Gen.| Races. |Gr.| No.|Gen.| Races.|Gr.| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+----+-----+----+---------+---+-----+----+-------+---+-----+----+----+----+----+----+----+----+----+----+----+

| 64 | 832| 4404| F3 | H × WL | 4| 5119| F3 | H × WL| 10| 14 | 1 | 1 | 1 | 2 | .. | .. | .. | 8 | 1 | 1 |

| 65 | 729| 913| F2 | Do. | 6| 936| F2 | Do. | 10| 16 | 5 | 6 | 16 | 2 | 5 | .. | 3 | 11 | 11 | 10 |

| 66 | 819| 57| F1 | P × M | 4| 1420| F2 | P × M | 10| 14 | 3 | 2 | 4 | .. | .. | 1 | .. | 3 | 5 | 1 |

| 67 | 832| 505| F1 | (H × L)L| 4| 5119| F3 | H × WL| 10| 14 | 2 | 2 | 3 | 3 | 2 | .. | 2 | 2 | 2 | 4 |

| 68 | 729| 935| F2 | H × WL | 4| 936| F2 | Do. | 10| 14 | 3 | 5 | 4 | 0 | 3 | 2 | 5 | 12 | 15 | 3 |

| 69 | 756| 2011| F2 | HPMWL | 4| 444| F2 | Do. | 10| 14 | .. | .. | .. | 1 | .. | 1 | .. | 1 | 4 | 3 |

| 70 | 807| 185| F1 | P × M | 4| 3894| F3 | P × M | 9| 13 | 4 | 2 | .. | .. | .. | 2 | 1 | 1 | 2 | 1 |

| 71 | 756| 1048| F2 | Do. | 3| 1390| F2 | Do. | 10| 13 | .. | .. | 3 | .. | .. | .. | .. | .. | 2 | .. |

| 72 | 762| 505| .. | (H × L)L| 3| 444| F2 | H × L | 10| 13 | 1 | 1 | 3 | 1 | 1 | 2 | 2 | 2 | 3 | 4 |

| 73 | 762| 2011| F3 | HPML | 4| 2621| F2 | HPML | 9| 13 | .. | 1 | .. | .. | .. | .. | 1 | 1 | 3 | 1 |

| 74 | 813| 2271| F2 | H × WL | 5| 3904| F3 | H × WL| 7| 12 | 1 | 5 | 5 | 2 | 2 | 1 | 3 | 2 | 4 | 9 |

| 75 | 820| 984| F2 | H × L | 3| 4731| F3 | P × M | 9| 12 | .. | 5 | 4 | 2 | 5 | 1 | .. | 5 | 5 | 4 |

| 76 | 728| 2272| F2 | Do. | 10| 258| F1 | H × L | 2| 12 | 2 | 7 | 9 | 4 | 4 | 3 | 2 | 7 | 7 | 9 |

| 77 | 756| 1043| F2 | P × M | 2| 1390| F2 | P × M | 10| 12 | 5 | 5 | 3 | 2 | .. | .. | .. | 3 | 2 | 2 |

| 78 | 762| 505| .. | (H × L)L| 3| 2621| F3 | HPML | 9| 12 | 1 | .. | .. | .. | .. | 1 | .. | .. | .. | 3 |

| 79 | 803| 2250| F2 | H × L | 3| 7522| P. | Houd. | 9| 12 | .. | 5 | 2 | 2 | 4 | .. | .. | 4 | 9 | 6 |

| 80 | 803| 2254| F2 | Do. | 3| 7522| P. | Do. | 9| 12 | 6 | 6 | 4 | 1 | 2 | 1 | 1 | 3 | 6 | 3 |

| 81 | 769| 492| F1 | Do. | 2| 911| F2 | H × L | 9| 11 | 3 | 6 | 1 | 1 | .. | 2 | .. | .. | 1 | .. |

| 82 | 807| 1043| F2 | P × M | 2| 3894| F3 | P × M | 9| 11 | 9 | 4 | 2 | .. | 3 | 3 | .. | 6 | 6 | .. |

| 83 | 769| 2254| F2 | H × L | 1| 911| F2 | H × L | 9| 10 | 7 | 7 | 2 | 1 | .. | .. | 1 | 2 | 4 | 1 |

| 84 | 813| 935| F2 | Do. | 3| 3904| F3 | Do. | 7| 10 | 1 | 2 | .. | 4 | 4 | 3 | .. | 7 | 8 | 1 |

| 85 | 813| 5113| F3 | Do. | 3| 3904| F3 | Do. | 7| 10 | 4 | 5 | 5 | .. | 1 | 1 | 1 | 6 | 8 | 5 |

| 86 | 813| 5142| F3 | Do. | 3| 3904| F3 | Do. | 7| 10 | .. | 2 | .. | .. | .. | .. | .. | 1 | 1 | 3 |

| 87 | 813| 5122| F3 | Do. | 2| 3904| F3 | Do. | 7| 9 | .. | 1 | 2 | .. | 1 | .. | .. | 2 | 2 | 3 |

| 88 | 813| 7320| F3 | Do. | 2| 3904| F3 | Do. | 7| 9 | .. | 6 | 1 | .. | 1 | .. | .. | 2 | 5 | 2 |

| 89 | 813| 377| F1 | Do. | 1| 3904| F3 | Do. | 7| 8 | 10 | .. | 6 | 1 | .. | .. | 1 | 4 | 3 | .. |

| | | | | +----+----+----+----+----+----+----+----+----+----+

| | | | | Totals (641) | 68 | 86 | 80 | 29 | 38 | 24 | 23 | 95 |119 | 79 |

| | | | | Percentages |10.6|13.4|12.5| 4.5| 5.9| 3.7| 3.6|14.8|18.6|12.3|

| | | | | |\--------\/-------/|\-------------\/------------/|

| | | | | | 41.0 | 59.0 |

+------+----+-----+----+------------------------------------------+-------------------+-----------------------------+

TABLE 52.--_Distribution of frequency of grades of "openness" in

offspring when both parents are extracted dominants (extracted

DD × DD)._

[ABBREVIATIONS: H = Houdan; L = Leghorn; M = Minorca; P = Polish;

WL = White Leghorn.]

+------+----+---------------------+---------------------+-----+-------------------------------------------------+

| No. | No.+-----+----+------+---+-----+----+------+---+ gr. +----+----+----+----+----+----+----+----+----+----+

| | | No. |Gen.|Races.|Gr.| No.|Gen.|Races.|Gr.| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+----+-----+----+------+---+-----+----+------+---+-----+----+----+----+----+----+----+----+----+----+----+

| 91 | 729| 2016| F2 | HPLM | 10| 936| F2 | H × L| 10| 20 | .. | .. | .. | .. | .. | .. | .. | 4 | 6 | 5 |

| 92 | 729| 2255| F2 | H × L| 10| 936| F2 | Do. | 10| 20 | 3 | 3 | .. | .. | .. | 1 | 2 | 5 | 11 | 10 |

| 93 | 729| 2269| F2 | Do. | 10| 936| F2 | Do. | 10| 20 | .. | 1 | .. | .. | .. | 1 | .. | 3 | 9 | 13 |

| 94 | 729| 2324| F2 | HPLM | 10| 936| F2 | Do. | 10| 20 | 2 | 3 | .. | .. | 1 | 1 | .. | 5 | 16 | 7 |

| 95 | 756| 1067| F2 | P × M| 10| 1390| F2 | P × M| 10| 20 | .. | 1 | 3 | 2 | 1 | .. | .. | 1 | 1 | .. |

| 96 | 756| 1113| F2 | Do. | 10| 1390| F2 | Do. | 10| 20 | .. | .. | .. | .. | .. | .. | 1 | 4 | 8 | 4 |

| 97 | 762| 2014| F3 | HPLM | 10| 444| F2 | H × L| 10| 20 | .. | .. | .. | .. | .. | .. | .. | .. | 1 | 4 |

| 98 | 819| 1113| F2 | P × M| 10| 1420| F2 | P × M| 10| 20 | .. | .. | .. | .. | .. | .. | .. | 2 | 6 | 2 |

| 99 | 819| 4257| F3 | Do. | 10| 1420| F2 | Do. | 10| 20 | .. | .. | 2 | .. | .. | .. | .. | 4 | 4 | 3 |

| 100 | 832| 4732| F3 | H × L| 10| 5119| F3 | H × L| 10| 20 | .. | .. | .. | .. | .. | .. | .. | 2 | 1 | .. |

| 101 | 832| 6481| F3 | Do. | 10| 5119| F3 | Do. | 10| 20 | .. | .. | .. | .. | .. | .. | .. | 2 | 5 | 4 |

| 102 | 756| 369| F2 | P × M| 9| 1390| F2 | P × M| 10| 19 | .. | 2 | .. | .. | .. | .. | .. | .. | 1 | 1 |

| 103 | 762| 2618| F2 | HPLM | 9| 444| F2 | H × L| 10| 19 | .. | .. | .. | .. | .. | .. | .. | 1 | 1 | .. |

| 104 | 762| 3776| F2 | H × L| 9| 444| F2 | Do. | 10| 19 | .. | .. | .. | .. | .. | .. | .. | 1 | 1 | .. |

| 105 | 832| 5803| F3 | Do. | 9| 5119| F3 | Do. | 10| 19 | .. | .. | 1 | 1 | .. | .. | 1 | 6 | 9 | 6 |

| 106 | 807| 1067| F2 | P × M| 10| 3894| F3 | P × M| 9| 19 | .. | 1 | 1 | 1 | 2 | 1 | 2 | 1 | 4 | 2 |

| 107 | 762| 2333| F3 | HPLM | 8| 444| F2 | H × L| 10| 18 | .. | .. | .. | .. | .. | .. | 1 | 2 | 5 | 4 |

| 108 | 762| 2618| F2 | Do. | 9| 2621| F3 | HPLM | 9| 18 | .. | .. | .. | .. | .. | .. | 1 | 2 | 2 | .. |

| 109 | 762| 3776| F2 | H × L| 9| 2621| F3 | Do. | 9| 18 | .. | .. | .. | .. | 1 | .. | 2 | 4 | 4 | .. |

| 110 | 819| 5674| F2 | P × M| 8| 1420| F2 | P × M| 10| 18 | 1 | .. | 1 | .. | .. | .. | 2 | 1 | 3 | 2 |

| 111 | 820| 2016| F2 | HPLM | 9| 4731| F3 | Do. | 9| 18 | .. | .. | .. | .. | 1 | .. | 1 | 1 | 4 | .. |

| 112 | 820| 2255| F2 | H × L| 9| 4731| F3 | Do. | 9| 18 | .. | .. | .. | .. | .. | .. | 1 | 2 | 6 | 5 |

| 113 | 820| 6479| F3 | Do. | 9| 4731| F3 | Do. | 9| 18 | .. | .. | 1 | .. | 2 | 1 | 2 | 9 | 12 | 4 |

| 114 | 832| 2618| F2 | HPLM | 8| 5119| F3 | H × L| 10| 18 | 1 | 1 | 3 | 4 | .. | .. | .. | .. | 12 | 3 |

| 115 | 832| 3776| F2 | H × L| 8| 5119| F3 | Do. | 10| 18 | .. | 3 | 3 | .. | 2 | .. | .. | .. | .. | .. |

| 116 | 834| 2324| F2 | HPML | 9| 5090| F2 | Do. | 9| 18 | .. | 1 | .. | .. | .. | 1 | .. | 10 | 10 | 3 |

| 117 | 762| 2333| F3 | HPLM | 8| 2621| F3 | HPLM | 9| 17 | .. | .. | .. | .. | 1 | .. | 1 | .. | .. | 1 |

| 118 | 807| 5075| F2 | P × M| 7| 3894| F3 | P × M| 9| 16 | .. | 1 | .. | .. | 2 | 1 | .. | 5 | 7 | 7 |

| 119 | 820| 5143| F3 | H × L| 7| 4731| F3 | Do. | 9| 16 | 1 | 1 | 2 | 5 | .. | 1 | 3 | 10 | 10 | 12 |

| 120 | 813| 2272| F2 | Do. | 9| 3904| F3 | H × L| 7| 16 | 1 | 1 | 1 | .. | 1 | .. | 2 | 5 | 7 | 7 |

| | | | | +----+----+----+----+----+----+----+----+----+----+

| | | | | Totals (472) | 9 | 19 | 18 | 13 | 14 | 8 | 22 | 93 | 169| 105|

| | | | | Percentages | 1.9| 4.0| 3.8| 2.8| 3.0| 1.7| 4.7|19.8|36.0|22.3|

+------+----+-----+----+--------------------------------------+----+----+----+----+----+----+----+----+----+----+

TABLE 53.--_Distribution of frequency of grades of "openness" in

offspring when both parents are heterozygous (RR × DR)._

+------+----+--------------------------------+--------------------------------+-------------------------------------------------+

| No. | No.+-----+----+--------------+------+-----+----+--------------+------+----+----+----+----+----+----+----+----+----+----+

| | | No.|Gen.| Races. |Grade.| No.|Gen.| Races. |Grade.| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+------+----+-----+----+--------------+------+-----+----+--------------+------+----+----+----+----+----+----+----+----+----+----+

| 121 | 728| 174| F1 | Houd. × Legh.| 1 | 1258| P. | Brah. × Tosa.| 2 | 2 | 7 | 2 | 1 | 1 | 1 | 1 | .. | .. | .. |

| 122 | 728| 912| F2 | Do. | 2 | 258| F1 | Houd. × Legh.| 2 | 7 | 3 | 3 | 2 | 1 | .. | .. | .. | .. | .. |

| 123 | 763| 3799| F1 | Min. × Houd. | 6 | 2247| F2 | Do. | 2 | .. | 2 | 2 | 2 | 2 | .. | 1 | .. | 2 | .. |

| 124 | 802| 509| F2 | Polish × Min.| 1 | 6652| F1 | Polish × Min | 4 | 6 | 6 | 1 | .. | 1 | .. | .. | .. | .. | .. |

| 125 | 802| 3846| F2 | Do. | 2 | 6652| F1 | Do. | 4 | 1 | 6 | 3 | 1 | 1 | .. | .. | .. | .. | .. |

| 126 | 802| 5025| F3 | Do. | 2 | 6652| F1 | Do. | 4 | 8 | 10 | 4 | 3 | 2 | .. | .. | .. | .. | .. |

| 127 | 802| 5087| F3 | Do. | 2 | 6652| F1 | Do. | 4 | 7 | 9 | 12 | 2 | .. | 1 | .. | .. | .. | 1 |

| | | | | +----+----+----+----+----+----+----+----+----+----+

| | | | | Totals (217) | 31 | 43 | 27 | 11 | 8 | 2 | 2 | 0 | 2 | 1 |

| | | | | Percentages |24.4|33.9|21.3| 8.7| 6.3| 1.6| 1.6| 0| 1.6| 0.8|

+------+----+-----+----+------------------------------------------------------+----+----+----+----+----+----+----+----+----+----+

TABLE 54.--_Distribution of frequency of grades of "openness" in

offspring when both parents are extracted recessives (extracted

RR × RR)._

+------+----+----------------------------------+--------------------------------+------+---------------+

| No. | No.+-------+----+--------------+------+-----+----+--------------+------+grade.+-------+-------+

+------+----+-------+----+--------------+------+-----+----+--------------+------+------+-------+-------+

| 128 | 728| [A]912| F2 | Houd. × Legh.| 2 | 1298| F2 | Houd. × Legh.| 1 | 3 | 3 | 3 |

| 129 | 827| 298| F2 | Pol. × Min. | 2 | 3852| F3 | Do. | 2 | 4 | 5 | 5 |

+------+----+-------+----+--------------+------+-----+----+--------------+------+------+---------------+

[A] _Cf._ Serial No. 12_a._

At the outset, then, we find (table 55) that even pure races with

high nostril (Polish, Houdans), when bred together, vary much in the

height of nostril (in perfection of dominance) and, in 2 per cent of

the offspring, even show the typical narrow nostril (fig. B, _a_). On

the other hand, in the narrow-nostriled races I have never obtained

any such variation. The most deviation that I have seen from grade

1 is found in my strain of Dark Brahma bantams that frequently give

grade 2. The variability of the high nostril, the stability of the

low nostril, is _prima facie_ evidence that the former is due to the

presence of a particular factor and the latter to its absence.

[Illustration: Fig. B.--Polygons of frequency of grades of

"openness" of nostril in offspring of various parents. _a_,

Both parents pure bred dominants; _b_, both parents extracted

dominants; _c_, one parent heterozygous, the other a dominant;

_d_, both parents heterozygous; _e_, dominant by recessive; _f_,

heterozygous by recessive; _g_, heterozygous by extracted

recessive; _h_, extracted recessives; _i_, heterozygous by

dominant; _k_, both parents second generation hybrids.]

Next, the heterozygotes of F1 (table 46), may be appealed to; but

they will give no critical answer. For expectation, dominance being

imperfect, is that the hybrids will be intermediate, and the result

will be the same whichever extreme grade is taken as dominant. The

empirical mode in the distribution of the offspring is at grade 2.

This implies much greater imperfection of dominance on the hypothesis

that grade 10 is dominant than on the hypothesis that grade 1 is

dominant; but this very fact supports the former hypothesis, since

imperfection of dominance is obviously a feature of the character

with which we are dealing.

The critical test is afforded by the F2 generation (tables 48 and

49). By hypothesis, 25 per cent of the offspring are expected to be

pure ("extracted") recessives, and the same number pure dominants;

and also, by hypothesis, the recessives are massed at or near one

grade while the dominants are variable. Now, as a matter of fact,

the upper 25 per cent range over 5 to 7 grades, while the lower 25

per cent are nearly massed in grade 1 (21 per cent are so massed in

one table, 17 per cent in the other). Therefore, in accordance with

hypothesis we must regard the lower grade--narrow slit--as recessive.

Similarly, heterozygous × low nostril (table 47) should give, on our

hypothesis, 50 per cent low nostril. If that is recessive we should

expect a massing of this 50 in the first two grades; if dominant a

greater scattering. The former alternative is realized. Again, in the

heterozygous × high nostril hybrid (table 50) the upper 50 per cent

will be massed or scattered according as high nostril is recessive

or dominant. Allowing for the 50 per cent heterozygotes in the

progeny, the 50 per cent of high nostrils are scattered through at

least 8 grades of the possible 10. High nostril is dominant. Finally,

extracted high nostrils bred together produce offspring (table

52) with a great range of variability (through all grades), while

extracted low nostrils (unfortunately all too few) give progeny with

grades 1 and 2 (table 53; fig. B, _h_). Accepting, then, the general

principle of the greater variability of the dominant character, we

have demonstrated conclusively that high nostril, or rather the

factor that determines high nostril, is dominant.

Comparing tables 45 to 54, we see that recessive parents are

characterized by a low grade of nostril and they, of course, tend

to produce offspring with a low grade. Similarly, dominants have a

high grade and tend to produce offspring of the same sort, while

heterozygous parents are of intermediate grade and their children

have nostril grades that are, on the average, intermediate. Without

regarding the gametic constitution, we might conclude, with Castle,

that offspring inherit the grade of their parents, and consequently

it would be possible to increase the grade, perhaps indefinitely, by

breeding from parents with the highest grade. Considering the gametic

constitution of the parents, it is obvious that such a conclusion

is premature. To get an answer to the question it is necessary to

find if there is, inside of any one table, among parents of the same

gametic constitution, any such relation between parental and filial

grades. This can be determined by calculating the correlation between

the grades of parents and progeny. Such calculation I have made for

table 48 with the result: index of correlation, _r_ = 0.018 ± 0.032,

which is to be interpreted as indicating that no correlation exists;

and in so far the hypothesis of Castle proves not to apply in the

cases of booting and doubt is thrown on the significance of his

conclusion.

Finally, if we throw together the frequency distributions of all

tables into one table (table 55; compare fig. B) we shall find the

totals instructive. Table 55 shows that, when all results are thrown

together, including hybrids of all sorts, grade 2 and grade 9 are

the most frequent and grade 6 is the least frequent, the frequency

gradually rising towards the extremes of the series. The same result

appears in the individual series that range from grade 1 to grade

10. What is the meaning of this result? It seems to me to bear but

one interpretation, namely, that there are only two centers of

stability--about grades 1 and 9--and true blending of these grades,

giving an intermediate condition, does not occur. Otherwise, in

consequence of the repeated hybridization, the intermediate grades

must be the commonest instead of the rarest. There is alternative

inheritance of the nostril height.

TABLE 55.--_Summary of tables 45 to 54._

+---------------------------------------------------------------------------------------------------------------------------+

| ABSOLUTE FREQUENCIES. |

+-------+------------------------------+----------------+-------------------------------------------------------------------+

| Table | Nature of mating (parental | Nature of +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-------+

| No. | nostril). | mating. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Total |

+-------+------------------------------+----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-------+

| 45 | High × high | D × D | 2 | 2 | 1 | 1 | 6 | 5 | 8 | 28 | 39 | 27 | 119 |

| 46 | High × low | D × R | 13 | 19 | 9 | 7 | 2 | 4 | 1 | 1 | ... | ... | 56 |

| 47 | Heterozygous × low | DR × R | 23 | 14 | 9 | 2 | 4 | ... | 1 | ... | ... | ... | 53 |

| 48 | Heterozygous × heterozygous | DR × DR | 90 | 140 | 86 | 20 | 21 | 18 | 9 | 13 | 17 | 6 | 420 |

| 49 | Do. | F2(DR × DR) | 117 | 171 | 129 | 54 | 40 | 11 | 19 | 39 | 57 | 41 | 678 |

| 50 | Heterozygous × high | DR × D | 10 | 13 | 10 | 5 | 4 | 1 | 2 | 8 | 6 | 2 | 61 |

| 51 | Do. | DR × DD | 71 | 96 | 73 | 30 | 39 | 24 | 23 | 95 | 119 | 68 | 638 |

| 52 | Extra high × high | DD × DD | 9 | 19 | 18 | 15 | 14 | 8 | 22 | 93 | 169 | 105 | 472 |

| 53 | Heterozygous × extracted low | DR × RR | 40 | 35 | 26 | 7 | 3 | 1 | ... | ... | ... | ... | 112 |

| 54 | Extra low × low | RR × RR | 8 | 8 | ... | ... | ... | ... | ... | ... | ... | ... | 16 |

| | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-------+

| | Totals | | 378 | 512 | 361 | 141 | 133 | 72 | 85 | 277 | 407 | 249 | ... |

+-------+------------------------------+----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-------+

| PERCENTAGES. |

+-------+------------------------------+----------------+-------------------------------------------------------------------+

| Table | Nature of mating (parental | Nature of +------+------+------+------+-----+-----+------+------+------+------+

| No. | nostril). | mating. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

+-------+------------------------------+----------------+------+------+------+------+-----+-----+------+------+------+------+

| 45 | High × high | D × D | 1.7 | 1.7 | 0.8 | 0.8 | 5.0 | 4.2 | 6.7 | 23.5 | 32.8 | 22.7 |

| 46 | High × low | D × R | 23.2 | 34.0 | 16.1 | 12.5 | 3.6 | 7.1 | 1.8 | 1.8 | ... | ... |

| 47 | Heterozygous × low | DR × R | 43.4 | 26.4 | 35.9 | 3.8 | 7.6 | ... | 1.9 | ... | ... | ... |

| 48 | Heterozygous × heterozygous | DR × DR | 21.5 | 33.3 | 20.5 | 4.8 | 5.0 | 4.3 | 2.1 | 3.1 | 4.1 | 1.2 |

| 49 | Do. | F2(DR × DR) | 17.3 | 25.2 | 19.0 | 8.0 | 5.9 | 1.6 | 2.8 | 5.8 | 8.4 | 6.1 |

| 50 | Heterozygous × high | DR × D | 16.4 | 21.3 | 16.4 | 8.2 | 6.6 | 1.6 | 3.3 | 13.1 | 9.8 | 3.3 |

| 51 | Do. | DR × DD | 11.1 | 15.1 | 11.4 | 4.7 | 6.1 | 3.8 | 3.6 | 14.9 | 18.7 | 10.7 |

| 52 | Extracted high × high | DD × DD | 1.9 | 4.0 | 3.8 | 3.2 | 3.0 | 1.7 | 4.7 | 19.7 | 35.8 | 22.2 |

| 53 | Heterozygous × extracted low | DR × RR | 35.8 | 31.3 | 23.2 | 6.3 | 2.7 | 0.9 | ... | ... | ... | ... |

| 54 | Extracted low × low | RR × RR | 50.0 | 50.0 | ... | ... | ... | ... | ... | ... | ... | ... |

+-------+------------------------------+----------------+------+------+------+------+-----+-----+------+------+------+------+