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Updated: June 24, 2025
But only the useful will stand further test, and if they find suitable conditions will become specific or varietal characters. On this conclusion it becomes at once clear, why natural dimorphism is, as a rule, a very useful quality, while the cultivated dimorphous varieties strike us as something unnatural.
I will describe this double stage of the organism by the phrase 'larval dimorphism. The initial form, that issuing from the egg, I will call 'the primary larva; the second form shall be 'the secondary larva. Among the Anthrax flies, the function of the primary larva is to reach the provisions, on which the mother is unable to lay her egg.
Hybrid birds, production of. Hydrophobia, communicable between man and the lower animals. Hydroporus, dimorphism of females of. Hyelaphus porcinus. Hygrogonus. Hyla, singing species of. Hylobates, absence of the thumb in; upright progression of some species of; maternal affection in a; direction of the hair on the arms of species of; females of, less hairy below than males.
As an additional instance of dimorphism and probable double adaptation to unrecognized external conditions I might point to the genus Acacia. As we have seen in a previous lecture some of the numerous species of this genus bear bi-pinnate leaves, while others have only flattened leaf-stalks.
Huxley; development of the gyri and sulci. Brakenridge, Dr., on the influence of climate. Brandt, A., on hairy men. Braubach, Prof., on the quasi-religious feeling of a dog towards his master; on the self-restraint of dogs. Brauer, F., on dimorphism in Neurothemis. Brazil, skulls found in caves of; population of; compression of the nose by the natives of. Break between man and the apes.
On the mutation hypothesis, adaptation is purely accidental. T. H. Morgan considers that the appearance of two slightly different shades of eye colour in male and female in a culture of a fruit-fly in a bottle is sufficient to settle the whole problem of sexual dimorphism, and to supersede Darwin's complicated theory of sexual selection.
Other instances studied by the French investigator are Erythraea pulchella and Calamintha Acinos. Dimorphism is of universal occurrence in the whole vegetable kingdom. In some cases it is typical, and may easily be discerned from extreme fluctuating variability. In others the contrast is not at all obvious, and a closer investigation is needed to decide between the two possibilities.
Those wonderful cases on the ground floor illustrating mimicry, dimorphism and so forth, were new in our times, and we went through them with earnest industry and tried over our Darwinism in the light of that. Such topics we did exhaustively. But on the other hand I do not remember any discussion whatever of human sex or sexual relationships.
Oranges, treatment of, by monkeys. Orange-tip butterfly. Orchestia Darwinii, dimorphism of males of. Orchestia Tucuratinga, limbs of. Ordeal, trial by. Oreas canna, colours of. Oreas Derbianus, colours of. Organs, prehensile; utilised for new purposes. Organic scale, von Baer's definition of progress in. Orioles, nidification of. Oriolus, species of, breeding in immature plumage.
Age, in relation to the transmission of characters in birds; variation in accordance with, in birds. Agelaeus phoeniceus. Ageronia feronia, noise produced by. Agrion, dimorphism in. Agrion Ramburii, sexes of. Agrionidae, difference in the sexes of. Agrotis exclamationis. Ague, tertian, dog suffering from. Ainos, hairiness of the. Aitchison, Mr., on sheep. Aithurus polytmus, young of.
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