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Take the case of any two species which, when crossed, produced few and sterile offspring; now, what is there which could favour the survival of those individuals which happened to be endowed in a slightly higher degree with mutual infertility, and which thus approached by one small step towards absolute sterility?
In short, a sterile, treeless expanse, or "travesia" for such there are in the Chaco not barren because of infertility in the soil, but from the want of water to fertilise it. Withal, it is inundated at certain periods of the year by the river's overflow, but in the dry season parched by the rays of a tropical sun.
A priori, I should be disposed to expect a certain amount of infertility between some of the extreme modifications of mankind; and still more between the offsprings of their intermixture. A posteriori, I cannot discover any satisfactory proof that such infertility exists.
In the case of Oenothera muricata x biennis the differentiating units reduce the fertility to a low degree, threatening the offspring with almost complete infertility and extinction. But then we do not know whether these characters are really units, or perhaps only seemingly so and are in reality composed of smaller entities which as yet we are not able to segregate.
He says a young man from Washington gave a lecture at his college down in North Carolina, in which he informed them that the cause of infertility of soils is a poisonous substance excreted by the plant itself, and that this can be overcome by changing from one crop to another because the excrete of one plant, while poisonous to that plant, will not be poisonous to other plants of a different kind.
Wives possessed no other advantages over concubines than the right of inheriting; and domestic unions were formed without any reference to the nobler felicities of social intercourse. Hence infertility not only excited dislike, but was held to justify repudiation.
As they continued rapidly to decrease, and as they themselves thought that they should not perish so quickly elsewhere, they were removed in 1847 to Oyster Cove in the southern part of Tasmania. The infertility of the women is even a more remarkable fact than the liability of all to ill-health and death. At the time when only nine women were left at Oyster Cove, they told Mr.
Where there is unusual fertility, the play of vital activities is thereby shown to have deviated from the ordinary play of vital activities; and conversely, if there is infertility.
Here then is a legend that in Egypt a human victim was annually sacrificed to prevent the failure of the crops, and a belief is implied that an omission of the sacrifice would have entailed a recurrence of that infertility which it was the object of the sacrifice to prevent.
In our own day the reluctance of rich and self-indulgent women to bear children is undoubtedly a factor in the infertility of the leisured class. This brings us naturally to the second part of our discussion the consideration of the causes which lead to the increase or decrease of population.
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