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The great naturalist, Wallace, has insisted that some degree of difference favours fertility, but that a little more tends to infertility, and by applying this hypothesis to the facts as I have observed them I am led to believe that there is no biological difference between the Bantu and the European of a degree sufficient to produce any difference, one way or the other, in the fertility of the offspring of the two races, but proper statistics, continued over several generations, will, of course, be required to prove or disprove this conclusion.
Many problems in the abdominal area are caused by a toxic colon, including chronic back pain, ovarian cysts, infertility, birth abnormalities, bladder infections and bladder cancer, painful menstruation, fibroids and other benign growths as well as malignant ones, and prostatitis or prostate cancer.
Girou de Buzareingues crossed three varieties of gourd, which like the maize has separated sexes, and he asserts that their mutual fertilisation is by so much the less easy as their differences are greater. How far these experiments may be trusted, I know not; but the forms experimentised on, are ranked by Sagaret, who mainly founds his classification by the test of infertility, as varieties.
We fully agree with the general tenor of this weighty passage; but forcible as are these arguments, and little as the value of fertility or infertility as a test of species may be, it must not be forgotten that the really important fact, so far as the inquiry into the origin of species goes, is, that there are such things in Nature as groups of animals and of plants, whose members are incapable of fertile union with those of other groups; and that there are such things as hybrids, which are absolutely sterile when crossed with other hybrids.
Lessened fertility from changed conditions, as in the case of the Tasmanians, Maories, Sandwich Islanders, and apparently the Australians, is still more interesting than their liability to ill-health and death; for even a slight degree of infertility, combined with those other causes which tend to check the increase of every population, would sooner or later lead to extinction.
From these facts; from the great difficulty of ascertaining the infertility of varieties in a state of nature, for a supposed variety if infertile in any degree would generally be ranked as species; from man selecting only external characters in the production of the most distinct domestic varieties, and from not wishing or being able to produce recondite and functional differences in the reproductive system; from these several considerations and facts, I do not think that the very general fertility of varieties can be proved to be of universal occurrence, or to form a fundamental distinction between varieties and species.
"Yes, you are right in that," said the Chief, "we are just beginning to understand the chemistry of the soil, and we hope soon to have very complete proof of the advanced ideas we already have concerning the causes of the fertility and infertility of soils."
The infertility which may be observed in various dimorphic and trimorphic plants, when they are illegitimately fertilised, that is by pollen taken from stamens not corresponding in height with the pistil, differs much in degree, up to absolute and utter sterility; just in the same manner as occurs in crossing distinct species.
In the case of the horse and the ass, although mules are the hybrid offspring of the two, the mules themselves are sterile, and there are many similar cases, so that some naturalists have maintained that mutual infertility should be recognised as the test of separation in species. Darwin founded his theory on the assumption that differences of species were differences of adaptation.
Zennor, indeed, was formerly known as the place "where the cow ate the bell-rope," a sportive neighbourly reference to its poverty and infertility. But the most famous feature of the church is its carved mermaid. There are two good old bench-ends, now forming the sides of sedilia, and of these the mermaid is one, represented with comb, mirror, and fishy tail.