Page:Popular Science Monthly Volume 68.djvu/497

Rh black. The ornithologists have not yet agreed on a subdivision of this species into larger northern or smaller southern subspecies, nor have the darker specimens from regions of greater rainfall received distinct names. Similar variations have been noted in the Hudsonian chickadee (Parus hudsonius) and in other birds of the northern forests. To what extent the variations seemingly due to direct influence of climate are hereditarv has not been ascertained.

While the embryo may be deprived of its normal growth momentum, the effect of unfavorable conditions is spent with a few generations of normal life, and no direct change in the heredity of the race is known to arise from the direct effects of environment.

Elaborate experiments in the effects of the underfeeding of silkworms have been made by Professor Vernon L. Kellogg and Mrs. Ruby Green Smith. The following synopsis of the results is given by Mrs. Smith.

The effects of underfeeding (which have been studied in heredity) upon the immediate generation fed on half the normal supply of food, may be classified as (1) physiological and as (2) those subject to quantitative measurement. They are as follows:

I. Physiological:

II. Variations from the normal which are subject to quantitative measurements.

The results of underfeeding in heredity have been studied in three generations derived from the original underfed great-grandparental stock. The characters which the underfeeding was known to affect were studied in a comparative way in 1904 among numerous lots.

Heredity of underfeeding among silkworms whose make-up may be summarized as follows:

Throughout these lots the conclusions were consistent, and were in brief as follows: