584 THE POPULAR SCIENCE MONTHLY. 



facts, we should be near to an understanding of the difference between 

 a high and a low organism ; the life is high when there is a high 

 degree of correspondence with a highly complex environment. 



Poets have understood this principle better, perhaps, than physi- 

 ologists. 



" Who has no inward beauty none perceives, 

 Though all around is beautiful " 



says Wordsworth ; and Coleridge 



"... We receive but what we give ; 

 And in our lives alone does Nature live ! " 



Emerson also embodies this whole philosophy in a single illustra- 

 tion : " The sea drowns both ship and sailor, like a grain of dust, and 

 we call it fate ; but let him learn to swim, let him trim his bark, and 

 the water which drowned it will be cloven by it and will carry it like 

 its own foam a plume and a power." 



When we remember that our environment consists, not only of 

 the natural elements of earth and sky, reaching to the most distant 

 star which communicates its vibrations to our atmosphere, but that 

 it also includes other human beings with the influences which such 

 an environment involves, we realize that, while physiology undoubted- 

 ly rests on chemistry and physics, it also includes psychology and 

 reaches far toward sociology sciences which involve the highest prob- 

 lems of our existence ; and, though we find it impossible to sink our 

 plummet to the depths of this ocean, or to send an arrow to the stars 

 which gem the arching dome above, we may at least hope to gather 

 a few shells on the shore of the one, and to intercept some gleams of 

 light from those distant suns which fascinate by their very distance, 

 and make glorious the night of our intellectual darkness even. 



How, we next inquire, does the human embryo differ, at the pro- 

 gressive stages of its evolution, from the embryos of the various lower 

 types which it successively resembles ? Whence the impulse of devel- 

 opment by which it rises from these lower levels to the human plane ? 

 In reply to these questions we can only refer to the principle of hered- 

 ity which, though it imprints upon the germ no trace discoverable 

 by any known test, unfailingly molds the plastic protoplasm into cer- 

 tain prescribed and prearranged forms, with their accompanying ca- 

 pacities and powers. The inherent forces by which one germ develops 

 into an oak and another into a trailing vine, one into a mollusk and 

 another into a man, are handed down from generation to generation, 

 so that each plant and animal reproduces its own kind and not some 

 other kind. This can not be regarded, however, as an exceptional 

 fact ; the production of the germ with all its hidden possibilities, like 

 every other differentiation of matter, depends upon the general prin- 

 ciple known as the persistence of force ; and to deny that the power 

 of development of any grade of life is inheritable is to deny the per- 



