I have collected so large a body of facts...showing...that with animals and plants a cross between different varieties, or betwe
en individuals of the same variety but of another strain, gives vigour and fertility to the offspring; and on the other hand, that close interbreeding diminishes vigour and fertility; that these facts alone incline me to believe that it is a general law of nature that no organic being fertilizes itself for a perpetuity of generations; but that a cross with another individual is occasionally—-perhaps at long intervals of time—indispensable. In this sentence from the third paragraph of the passage, what does perpetuity mean? A) gratefulness B) consideration C) a temporary state D) time without end; eternity
