ORGANIC DEPENDENCE AND DISEASE 13 



On this point our present knowledge permits us to lay 

 emphasis, namely, that on the whole, in the survey of the 

 earth and the sum total of its multitudinous and inconceiv- 

 ably variant groups of life, there has been a strong mini- 

 mum, a redeeming minority, of competent upward evolu- 

 tion; and wise students of nature, in reflecting on this 

 thought, have broken out into exclamations of wonder and 

 amazement at the slender thread of chance by which we 

 who call ourselves men have come to this estate, in a world 

 where for millions of years the temptation to the easier 

 way and the obstacles to independent living were con- 

 stantly against us. 



Let us look at a most common illustration of the general 

 fact of dependence among existing races of animal life, of 

 very ancient ancestry. The oyster is early attached firmly 

 to the sea bottom, to the rock or to the shell of a brother 

 oyster and never stirs from its moorings for the rest of its 

 life. It opens its hard valves a little way to let its servants, 

 the food-bearing water currents, deliver their nutrient 

 supplies and it defends itself in the struggle against en- 

 emies, not by standing out in the open and meeting force 

 with force but simply by closing its doors and shutting itself 

 up in its calcareous caisson. To the attacks of sharp- 

 toothed fishes and the relentless starfish the oyster has lit- 

 tle defense. The nonresistant, flaccid, pacific creature 

 within, fully equipped with the organs of special physiol- 

 ogy, is essentially the same in habit as he was those millions 

 of years ago when the oysters began to show themselves in 

 the salt waters of the Carboniferous age. The knell of its 

 progress was struck when first it settled down to a fixed 

 immobile existence and, hopeless as the ox, the future holds 

 for it no promise of improvement. And yet even today the 

 embr^^o oysters have a brief period of locomotive freedom, 

 proof enough in the laws of ontogeny that a free life was 

 once the ancestral condition of the race. With the oyster's 

 cousin, the clam, the case is similar ; less degenerate in phys- 



