11. We reply, that to work in vain, in the sense of producing means of life which are not used, embryos which are never vivified, germs which are not developed; is so far from being contrary to the usual proceedings of nature, that it is an operation which is constantly going on, in every part of nature. Of the vegetable seeds which are produced, what an infinitely small proportion ever grow into plants! Of animal ova, how exceedingly few become animals, in proportion to those that do not; and that are wasted, if this be waste! It is an old calculation, which used to be repeated as a wonderful thing, that a single female fish contains in its body 200 millions of ova, and thus, might, of itself alone, replenish the seas, if all these were fostered into life. But in truth, this, though it may excite wonder, cannot excite wonder as anything uncommon. It is only one example of what occurs everywhere. Every tree, every plant, produces innumerable flowers, the flowers innumerable seeds, which drop to the earth, or are carried abroad by the winds, and perish, without having their powers unfolded. When we see a field of thistles shed its downy seeds upon the wind, so that they roll away like a cloud, what a vast host of possible thistles are there! Yet very probably none of them become actual thistles. Few are able to take hold of the ground at all; and those that do, die for lack of congenial nutriment, or are crushed by external causes before they are grown. The like is the case with every tribe of plants.[3] The like with every tribe of animals. The possible fertility of some kinds of insects is as portentous as anything of this kind can be. If allowed to proceed unchecked, if the possible life were not perpetually extinguished, the multiplying energies perpetually frustrated, they would gain dominion over the largest animals, and occupy the earth. And the same is the case, in different degrees, in the larger animals. The female is stocked with innumerable ovules, capable of becoming living things: of which incomparably the greatest number end as they began, mere ovules;--marks of mere possibility, of vitality frustrated. The universe is so full of such rudiments of things, that they far outnumber the things which outgrow their rudiments. The marks of possibility are much more numerous than the tale of actuality. The vitality which is frustrated is far more copious than the vitality which is consummated. So far, then, as this analogy goes, if the earth alone, of all the planetary harvest, has been a fertile seed of creation;--if the terrestrial embryo have alone been evolved into life, while all the other masses have remained barren and dead:--we have, in this, nothing which we need regard as an unprecedented waste, an improbable prodigality, an unusual failure in the operations of nature: but on the contrary, such a single case of success among many of failure, is exactly the order of nature in the production of life.