ORGANIC DEPENDENCE AND DISEASE 35 



independence here indicated is essentially that of the Cam- 

 brian fauna as a whole is an indication of how slowly sub- 

 jection and dependence permeated the life of the earth. 



THE BEGINNINGS OF SYMBIOSIS AND 

 PARASITISM 



In the foregoing we have endeavored to indicate that de- 

 pendence is not a primitive but a secondary condition of 

 organisms; that, as the alternate state to independence, it 

 had involved in lesser degree even so early a fauna as the 

 Cambrian ; and in successive faunas to the present we have 

 the full knowledge that it has vastly increased in its scope 

 and effect. We have no reason to believe that the depend- 

 ent habit of life once acquired has ever been fully removed 

 or lost ; it is safe to say that dependence, under the normal 

 procedure of the organic law, is incurable; an adaptation 

 without escape. 



We are now to consider, not the expressions of race de- 

 pendence, but those consociations among early animals 

 which have led from conditions of mutual support and in- 

 terdependence (symbiosis) into conditions of parasitism or 

 absolute dependence of one animal or plant upon another's 

 vital functions. From the protozoa and bacteria to man 

 and the oak, nature is riddled with such expressions of de- 

 pendence and surrender. 



In the more innocent expressions of symbiosis termed 

 mutualism and commensalism, where associations of or- 

 ganisms are purely social and apparently harmless or even 

 mutually advantageous to the participants, it is probable 

 that once fixed the outcome is infallibly deleterious. 



The glass-rope sponge (Hyalonema) has its coil of rope 

 by which it anchors itself to the sea bottom, incrusted and 

 shielded by a coral (Palythoa), which spreads like a thin 

 wrap of felt all about it, while its ally the Venus 's Flower- 



