Page:Popular Science Monthly Volume 39.djvu/66

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BUT now—if Nature has indeed never stopped her operations at any one time—if they have been, on the contrary, always continuous in unity of plan amid every change in method, then it follows that we do not know how often new germs may have been introduced and may have had their full development accelerated by processes of comparatively short duration. Darwin, in a passage but little noted, has thought of this. He speaks of stages of development being possibly "hurried through."[1] We see this actually done in the living world, although we do not often think of it as we ought. It is done in all the mysterious phenomena of metamorphosis. A comparatively low and simple organism goes to sleep, and in a few weeks—or a few days, or even, it may be, in a few hours—it awakes entirely reformed, reconstructed, provided with new organs, and fitted for absolutely new spheres of activity and life. We do not know whether this method of creation may not have been repeated over and over again with abiogenic germs—just as it is now repeated in an infinite variety of forms among the germs which are biogenic. I am contending now for a true and honest agnosticism and not for any theory. We do not know that inheritance by descent is the only possible or the only actual cause of likeness and homologies in organic structure. It is not the cause of it as regards the inorganic world, and it may not be the only cause of it in those houses which have been made out of inorganic materials to be the abodes of life. It is indeed not possible that inheritance can be the only cause of likeness—if it be granted that the first starting-point of development must have been in germs which had no organic parent. On the other hand, we can be quite certain of the reason why organs should be made like each other, although we can not be sure of the physical causes through which exclusively this likeness must be brought about. The reason is that certain needs must be met by appropriate apparatuses—vital, chemical, and mechanical. Extraneous matter must be assimilated, weight must be supported, circulating fluids must be supplied with oxygen, light must be caught upon adapted surfaces, and must be transmitted through focused lenses, if sight is to be enjoyed. And so on. The Why is within our knowledge. The How is most doubtful and most obscure. Geology, above all other sciences,

  1. Origin of Species, sixth edition, p. 149.