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Updated: May 16, 2025
Davenport has concluded that there are two double factors for black pigmentation in the full-blooded negro which are separately inheritable. The determinants of the red and yellow have still to be worked out. The moistness of the skin, as perspiration, depends upon the number and activity of the sweat glands.
In short, viewing the internal secretions as determinants, by their quantitative variations, of a host of biologic phenomena furnishes a concrete and detailed foundation for Darwin's theory of pangenesis. Darwin's theory of pangenesis was an attempt to harmonize everything known in his time about heredity.
If I were called upon to exhibit the chief determinants of human life as a single chain of causes and effects a simplification of the historical problem, I may say at once, which I should never dream of putting forward except as a convenient fiction, a device for making research easier by providing it with a central line I should do it thus.
According to Weismann, the individual parts and characteristics of the organism are represented in the germ-plasm, not in finished form, but as “determinants” in a definite system which is itself the directing principle in the building up of the bodily system, and with definite characteristics, which determine the peculiarities of the individual organs and parts, down to scales, hairs, skin-spots, and birth-marks.
The reason why the determinants give rise to the original structure first and then change it into the new structure is probably the same as that which causes secondary sexual characters to develop only at the stage of puberty. By the hypothesis the new habits and new stimuli begin to act at some stage after the complete development of the original structure of the body.
Therefore there can be no inheritance of acquired characters, and no modifications of type through external causes; and all variations which appear in a series of generations are due solely to internal variations in the germ-cells, whether brought about by the complication of their system through the fusion of the male and female germ-cells, or through differences in the growth of the individual determinants themselves.
The dreams of conquest which are the real essence of all imperialism are thus supported in Germany by arguments peculiar to Germans. But the arguments put forward are not the real determinants of the attitude. The attitude, in any country, whatever it may be called, rests at bottom on sheer national vanity.
And thus there comes about a “struggle” and a process of selection among the determinants, the result of which is expressed in changes in the determinates, in the direction of greater or less development.
Pushing up against them, the head of a sperm cell, consisting almost entirely of the nucleus of the cell and carrying the determinants which were to decide one-half of its future characters, penetrated this egg and fused with its nucleus. This was filled with the determinants of the characters inherited from the mother.
Reversed specimens occasionally occur in many species of Pleuronectidae, and if the determinants for a reversed head and a normal body were united in one zygote, the curious abnormality observed might be the result.
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