in the earlier than in the later years. This may be due to the smaller numbers of birds competing in the earlier years. The greatest differences between the highest and lowest records occurred in 1916 when 268 eggs separated the extremes and in 1919 when the difference was 262 eggs. The least range was that of 1912, when the difference between highest and lowest was only 139 eggs, but this is based on only fifteen records. The large range of egg production found in the combined records for the nine years is probably not due to any single year, but is a regular feature encountered in each group of birds submitted.

7 22 37 52 67 82 97 112 127 142 157 172 187 202 217 232 247 262 277 292
Number of Eggs Laid

Fig. 1. Variation in annual egg production of 655 Barred
Rock pullets.

The general characteristics of variation in the egg production of this group are shown in the frequency curve in Fig. 1, and the constants in Table 2. The curve resembles in general the normal curve of error with the following exceptions. The single chief empirical mode in the class 180-194 is apparently preceded by a minor mode in the class 150-164, the two modes being separated by a lower frequency in the intervening class. This bimodal tendency is observable in the distributions for all nine years, although the position of the modes and the distances which separate them are not the same in each year. The general form of the curve is not greatly altered by omitting the data for the years 1913 and 1918 when condi

OF THE DOMESTIC FOWL

tions were not good. A tendency of this sort was observed in the frequency distribution of egg production in Rhode Island Red pullets and there it appeared to be due to the different kinds of fowls submitted by two classes of breeders i. e. those who entered only one or two contests and those who competed in many contests. Thinking that the same explanation might hold true for Barred Rocks, the data have been rearranged to show the distribution of fowls submitted by repeaters and single entrants. In the case of the Barred Rocks, one breeder had entered seven of the nine contests, and fifty-seven fowls from this single breeder completed a full year's laying. If the bimodal nature of the curve were due to the different records made by the fowls entered by repeating breeders and single entrants, the deletion of the records of this repeating breeder should partially correct the tendency. The data were therefore retabulated omitting the fifty-seven pullets entered by this breeder. This produced practically no change in the general character of the remaining distribution, except to constrict the curve somewhat at the upper end, since the fowls of this repeating breeder averaged 185 eggs as compared with 161 eggs for the remainder. The significant result of this separation of records was, however, the demonstration of a distinctly bimodal distribution of the fowls of this single breeder. The modes were in the classes centering at 157 and 202 eggs, or at practically the same points as the modes of the whole distribution. The fowls from this single source appeared to be of two different sorts; one group composed of average or mediocre lavers: and another group characterized by high egg production. We then tabulated separately the egg records of the fowls entered by other breeders which had entered four or more contests and found this same tendency in evidence in the distributions of all except one of these breeders. Grouping together the fowls of all repeating breeders produced a distribution with a major mode at 187 eggs and minor modes at 157 and 217. The tendency for the fowls to group themselves about more than one mode is evident then in the groups of fowls submitted both by repeating breeders and by those who entered but one contest. Of greater importance is the fact

that groups of fowls coming from a single breeder and pre-
sumably descended from related ancestors exhibit this same
tendency. We cannot attempt to establish or to explain this
tendency from the present evidence, but it points to several
interesting possibilities. It may be for example that the sys-
tem of double matings used to produce standard Barred Rocks
has perhaps operated on other traits as well as color in the pro-
duction of groups of females differing in fecundity. We have
not attempted to determine by fitting curves to the distribu-
tions obtained whether this tendency causes a significant de-
parture from the normal curve of error. The constants de-
scribing the other features of the curve as given in Table 2
resemble in general those deduced by Pearl and Surface (1909)
for another large group of Barred Rocks kept under somewhat
different conditions. These authors found that the departures
of their distributions from the normal curve were not very
marked. Our distributions likewise conform roughly to the
normal curve.

TABLE 2

SUMMARY OF VARIATION CONSTANTS FOR ANNUAL PRODUCTION.

Year

1911-12 54 150.06±3.31 36.02±2.34 24.01±1.65 148.33±4.19 144.87.144.10 1912-13 15 150.00 5.47 31.40±3.87 20.93±2.68 148.12±6.86 144.38+.179.20 1913-14 35 146.71 4.66 40.85±3.29 27.84±2.41 154.50 5.84 170.08-572.099 1914-15 57 151.214.81 53.88+3.40 35.63+2.52 151.88 6.03 153.22 -.037.109 1915-16 93 159.90 3.22 46.05±2.28 28.80±1.54 156.75±4.04 150.45+.205±.08: 1916-17 82 171.27 3.87 51.96+2.74 30.34+1.74 183.46 4.85 207.84-704.05 1917-18 100 174.55+2.45 36.25±1.73 20.77±1.03 176.25 +3.07 179.65 -.141.08 1918-19 120 159.50 2.68 43.53+1.90 27.29+1.27 164.17+3.36 173.51 -.322.06 1919-20 99 173.52 3.13 46.25 +2.22 26.65+1.36 173.91+3.92 174.69 -.025.08 All years 655 163.05-1.16 44.18 0.82 27.10-0.54 166.48+1.45 173.34-233-.03

The other constants descriptive of the distribution of fecundity in the contest Barred Rocks are given in Table 2. The mean or average egg production varied in different years from 146.7 eggs in 1913 (a year of poor conditions) to 174.5 in 1917. The average for all nine years was 163 eggs, or if the two years of poor conditions (1913 and 1918) are omitted. this average is 165 eggs. The absolute variability of the fowls

OF THE DOMESTIC FOWL

as measured by the coefficient of variation ranged from about 21 per cent in 1912 (although this is founded on only fifteen complete records) to 35.6 per cent for 1914. The variability of all fowls in the nine years was a little over 27 per cent. This is practically the same as the variability found in Wyandottes and Rhode Island Reds and is somewhat less than the variability of the Barred Rocks studied by Pearl and Surface (1909). The fact that such great variability in fecundity is found within a single variety of fowls indicates that the innate egg producing capacity of these fowls is very variable in spite of the selection practised by the competing breeders.

The median or that point which divides the total frequency distribution in two equal parts varied in the different years through a somewhat wider range than the mean and for the whole distribution has a value of 166.5. Half of the Barred Rocks submitted laid more than 166 eggs and half laid fewer.

mean.

The mode, or the commonest number of eggs laid by these fowls was 173 eggs for the combined data. Its value indicates that more fowls laid in the neighborhood of 173 eggs than any other number. Its position on the frequency curve (Fig. 1) is found to be between the two high points of the curve and it is significant only if this curve actually has a single mode and represents a single group of fowls. Assuming for the present that this is so, the position of the mode with reference to the mean is one indication of the relative importance of the departure of the curve from the normal. The mode is above the This can be readily seen from the frequency curve which ascends gradually to the mode and descends steeply thereafter. The fowls laying less than the modal number of eggs are scattered over a wide area between zero and 173, while the fowls which lay more than this number of eggs are concentrated in the relatively fewer classes between 173 and The measure of this tendency of the curve to bulge or be restricted on one or the other side of the mean is given by the skewness. In this case the mode is above the mean and concentration is in the higher producing classes. The skewness is of this negative type in all years in which this tendency is statistically significant (1913, 1916, 1918) while the

277.

the

skweness of the total distribution is also significantly negative, but actually small in amount (-23). The departure of this distribution from the zero skewness or symmetry of the normal curve is therefore not marked and in this respect likewise it resembles the distribution of the single flock of Barred Rocks studied by Pearl and Surface.

TABLE 3

CONSTANTS OF VARIATION IN FIRST YEAR EGG PRODUCTION OF Barred ROCK PULLETS AT OTHER PLACES.

1)

2)

3)

4)

Bulletin 338 N. J. Agr. Exp. Station, Oct. 1, 1919. Replacements included.
eggs .81 to be added to the mean.
Ten bird pens.

Bulletin 110, Part 1, U. S. Dept. Agr. Bur. Animal Industry pp. 25, 28.
bird pens).

This bulletin. Ten bird pens. Replacements omitted. Out eggs 2.2%.

Percent of out

Large flocks. 50

Replace

Bulletins 111, 114, 118, 123, and 131 Dept. Agr. New South Wales. Egg Laying Test at Hawkesbury Agricultural College and Experiment Farm, Richmond, N. S. W. ments included. Out eggs not reported. Six pens.

5) Report of the Canadian Egg Laying Contest held at the Experiment Farm at Ottawa, Ont. Replacements omitted. Out eggs 2.72%. Ten bird pens.

6)

7)

Report of the Manitoba Egg Laying Contest held at the Experiment Farm at Brandon, Man. Replacements omitted. Out eggs 1.62%. Ten bird pens. Report of the Quebec Egg Laying Contest held at the Experiment Station at Cap Rouge, Que. Replacements omitted. Ten bird pens. Out eggs 2.36%. 8) Report of the N. S. Federal Egg Laying Station N, S. Replacements omitted. 9) Report of the P. E. I. Egg Laving Contest town, P. E. I. Replacements omitted.

Contest held at the Experiment Farm at Nappon
Ten bird pens. Out eggs 2.06%.

conducted by the Experimental Station at Charlotte-
Ten bird pens. Out eggs 3.85%.