Page:The World as Will and Idea - Schopenhauer, tr. Haldane and Kemp - Volume 3.djvu/71

perpetuation of the forms stand open, and are secured and sustained by nature with boundless care and jealousy, generatio æquivoca still takes place, can only be decided by experience; especially since the saying, Natura nihil facit frustra, might, with reference to the paths of regular propagation, be used as a valid argument against it. Yet in spite of the most recent objections to it, I hold that at very low grades generatio æquivoca is very probable, and primarily indeed in the case of entozoa and epizoa, particularly such as appear in consequence of special cachexia of the animal organism. For the conditions of their life only appear exceptionally; consequently their species cannot propagate itself in the regular manner, and therefore has always to arise anew whenever opportunity offers. Therefore as soon as the conditions of life of epizoa have appeared in consequence of certain chronic diseases, or cachexia, and in accordance with them, pediculus capitis or pubis or corporis appears entirely of itself, and without any egg; and this notwithstanding the complex structure of these insects, for the putrefaction of a living animal body affords material for higher productions than that of hay in water, which only produces infusoria. Or is it thought more likely that the eggs of the epizoa are constantly floating about in the air in expectation? (Fearful to think of!) Let us rather remember the disease of phthiriasis, which occurs even now. An analogous case takes place when through special circumstances the conditions of life appear of a species which up till then was foreign to that place. Thus August St. Hilaire saw in Brazil, after the burning of a primitive forest, as soon as ever the ashes had cooled, a number of plants grow up out of them, the species of which was not to be found far and wide; and quite recently Admiral Petit-Thouars informed the Académie des sciences that upon the growing coral islands in Polynesia a soil gradually deposits itself which is now dry, now lies in water, and which vegetation soon takes possession of, bringing forth trees which are abso-