340 POPULAR SCIENCE MONTHLY. 



intelligent adaptations come into existence flash upon us like a 

 revelation. We look as with vision renewed upon the pine cone 

 in the forest, upon the flower shining amid the expanse of green, 

 upon the sudden lightning of the firefly, and the manifold hues of 

 insect and bird. For, little as we have attended to them before 

 save as the commonplaces of our knowledge, we now see that 

 they are paths of least resistance objectively embodied proto- 

 plasmic tools with which, in the silence of the unconscious world 

 the organic system is slowly but surely reaching its ends. And 

 as we ponder it becomes clear to us that the same system is 

 at work in the making of tools and the fashioning of organs 

 that, though the one process is conscious, the other unconscious, 

 they are deep down in the heart of them the expressions of but a 

 single method. Everywhere we find the evidences of this likeness 

 in the awl of the shoemaker and the tool of the boring insect ; 

 the earth-trap of the native African and the pitfall of the ant 

 lion ; the web of the spider and the net of the fisherman ; the 

 digging stick of the Australian, the foot of the mole, and the 

 spade of the navvy ; in the single oar of the boatman and the 

 sculling tail of the fish ; the sticky tongue of the anteater and the 

 slime pot of the human catcher of birds ; in the kayak of the sav- 

 age and the floating pupa skin of the gnat ; the scale armor of 

 the armadillo and the soldier's cuirass ; in the climbing hooks of 

 the tiger beetle, the claws of the bat, and the grappling irons used 

 in naval warfare; on the one hand, in the pulley, screw, and 

 wedge ; in chisels used in stonecutting, gravers with which wood 

 is carved, axes for felling trees ; in screwdrivers, lifting jacks, 

 Nasmyth hammers, battering rams ; the cord and weight of the 

 window sash, the wheels of carriages, and the rollers whereon 

 heavy masses are moved from place to place ; on the other hand, 

 in the muscles, sinews, and joints of animals ; in the wing of the 

 bird, the paddle of the porpoise, the hand of man, the mandible of 

 the ant, the horns of the cow, the lance of the swordfish, the 

 stinging cells of certain coelenterata, the channeled poison tooth 

 of the snake, or the defensive antennae of the spider ; even in the 

 vertebrate eye itself. For all these, being objective paths of least 

 resistance, are signs of a law that, pervading the realm of living 

 things, has its roots in the inorganic world, since it springs from 

 the very nature of motion as a result of differential stress. And 

 when adequate account is taken of the presence of end in organic 

 activities, of its absence from movements which are inorganic 

 account, that is to say, of the fundamental difference between 

 living protoplasm and inorganic matter then the whole of evolu- 

 tion, viewed apart from its secondary processes, may be summed 

 up in the simple formula movement in the direction of least re- 

 sistance. 



