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.
Food Variations of Silkworms
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.
I. Physiological:
| 1. | Larval moltings, pupation and emergence of adult delayed and metamorphosis thereby prolonged. |
| 2. | Fertility reduced (as indicated by number of eggs laid, number hatching and number of individuals reaching maturity). |
| 3. | Mortality in all stages greater than among normally-fed individuals. |
II. Variations from the normal which are subject to quantitative measurements.
| 1. | Reduction in size and weight of all parts in all stages (exemplified statistically and quantitatively by larval widths and lengths, by moth wing expanse, and by larval, pupal and adult weights). |
| 2. | Reduction in quantity of silk produced, the cocoons being below normal in dimensions, thickness and weight. |
| 3. | Degeneration of wing veins slightly more marked than in normally-fed individuals (economy of material being practised to advantage in these comparatively useless structures). |
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:
| 1. | Lots accustomed always to years of plenty. |
| 2. | Lots in which some one of the four generations experienced famine |
| 3. | Lots in which famine was experienced in two alternate or two successive years. |
| 4. | Lots in which famine was experienced in three successive or in one alternate and two successive years. |
Conclusions.
Throughout these lots the conclusions were consistent, and were in brief as follows:
| 1. | The lingering effects of a single generation of underfeeding may be definitely traced to the third generation, although the progeny of the underfed generation be given the optimum amount of food. |
