Vol. 7, 1921 
GENETICS: J. A. HARRIS ET AL. 
213 
the place of minima. The largest displacement occurred at about 5 mm. 
from the plate. 
Pressures in Smooth Straight Pipes. — These surveys in pitch and depth 
were completed for a number of telephone blown brass pipes, 1 cm. in 
diameter and of different lengths; but the very interesting graphs ob- 
tained must be omitted here. Thus the pipe 13 cm. long showed enormous 
maxima at a' and correspondingly large negative minima at d" ', at all 
depths (2, 4, 8, 12 cm.) below the mouth of the tube. Figure 11 reproduces 
the behavior of the same tube cut down to 10 cm. of length, at different 
depths 2, 4, 6, 8, 10 cm. below the mouth. Finally similar graphs for a 
variety of wide tubes and resonators have been worked out and progress 
made with the installation for symmetrical induction. 
THE PREDICTION OF ANNUAL EGG PRODUCTION FROM THE 
RECORDS OF LIMITED PERIODS 
By J. Arthur Harris, W. F. Kirkpatrick and A. F. Blaksslee 
Station for Experimental Evolution, Carnegie Institution, and the Storrs 
Agricultural Experimental Station 
Communicated by C. B. Davenport, March 12, 1921 
For the past several years the writers have been considering the possi- 
bility of predicting the annual egg production of the domestic fowl from the 
records of short periods of time. Such records may be determined by trap- 
nesting, or by the use of other criteria when the maternity of the eggs is not 
required for breeding purposes. 1 
The first definite step in the direction of the use of the egg record of a 
short period for the prediction of the production during a subsequent or a 
longer period was, as far as we are aware, taken in 1917 when it was shown 2 
that in a heterogeneous series of birds such as are submitted by practical 
breeders in egg laying contests, the October egg production is correlated 
with that of every other month of the year. The investigation was carried 
much further in a second memoir 3 in which the correlations between the 
records of the individual months and the production of the whole year, 
between the records of the individual months and those of the remaining 
11 months of the year, and between the production of 5 of the individual 
months and the production of all the other individual months, were pub- 
lished for two series of birds. In this paper the equations for the prediction 
of total annual production from the record of the individual months were 
given. 
Our purpose here is to state briefly the results of a first test of the possi- 
bility of utilizing the linear regression equation (which is strictly valid 
only for the population from which it is deduced) for the prediction of the 
records of the birds of a flock the performance of which is unknown as far 
as the determination of the constants of the equations is concerned. 
