380 ^ GENETICS: R. PEARL 
This woiild not be unexpected; but secondary fringes, or something 
else in th^ field, seem to remain stationary. Successive fields may be 
quite different as to arrangement of fine and coarse lines, but all plane 
gratings exhibit the same phenomena. Thus it is obvious that the 
fringes of the present paper result from a residual irregularity in the 
ruHngs of the grating. Micrometrically, the successive strips of a 
slit image, nowever fine, are of unequal intensity. Between these 
there is diffraction as may be tested by examining the clear glass at the 
edge of the ruled space. 
It is obvious that in the otherwise indistinguishable images of a slit 
in homogeneous light, however sharp or however narrow, in its own 
focal plane the nature of its origin still persists and may be detected by 
observations outside of the principal focal plane. A fine sHt is in all 
cases presupposed and all the phenomena vanish for a wide slit. On the 
other hand the width of the pencils of parallel rays may be far greater 
than is necessary to show the strong Fraunhofer lines. 
A fuller report of this work has been presented to the Carnegie In- 
stitution of Washington, D. C. 
i 
THE EFFECT OF PARENTAL ALCOHOLISM (AND CERTAIN 
OTHER DRUG INTOXICATIONS) UPON THE PROGENY 
IN THE DOMESTIC FOWL 
By Raymond Pearl 
BIOLOGICAL LABORATORY, MAINE AGRICULTURAL EXPERIMENT STATION 
Received by the Academy, June 7, 1916 
The investigation here reported deals with the general problem of the 
origin and causation of new, heritable variations. That this is one of 
the most fundamental problems of genetics admits of no doubt. The 
method by which this general problem is attacked in the present investi- 
gation is that of exposing systematically the germ-cells of an animal to 
something unusual or abnormal in the surrounding conditions, and 
then analyzing, so far as may be, not only the new heritable variations 
themselves (provided any such appear), but also the factors which 
under he their causation. 
The specific problems with which this investigation deals are these: 
1. Does the continued administration of ethyl alcohol (or similar 
narcotic poisons) to the domestic fowl induce precise and specific changes 
in the germinal material, such as to lead to new, heritable, somatic 
variations? 
