BIONOMICS 273 



manner; not multiform variations will arise, but deviations all 

 in one direction." 



Although he calls this " a simple reply," yet it is really 

 too indefinite to meet the argument. He has overlooked the 

 great and powerful influences working inconspicuously through 

 time, viz., the bio-economic or symbiogenetic influences which 

 are the perennial determinants of variation. Hence he is 

 obliged constantly to refer to "chance," or to dwell only on 

 secondary and local changes. 



That those various local influences which he enumerates 

 all have their effects is, of course, undeniable, but to what an 

 extent they are indeed neutralised and outclassed by the 

 perennial symbiogenetic influences is quite a different matter, 

 and one which he hardly helps us to determine. 



Just as men of slightly-unlike dispositions behave in quite opposite 

 ways under the same circumstances, or just as men of slightly-unlike 

 constitutions get diverse disorders from the same cause, and are 

 diversely acted on by the same medicine; so the insensibly-differentiated 

 members of a species whose conditions have been changed may at once 

 begin to undergo various kinds of functional changes. 



All of which contains much that is true, though not 

 unqualifiedly true, and of secondary importance. The bond of 

 symbiogenesis, in spite of all organismal vagaries, as we have 

 seen, unites all strenuous organisms and tends to keep them on 

 the straight path, and frequently in spite of themselves, as one 

 might say. The arrival of physical disorders is not a matter 

 of mere chance, but a matter of transgression of biological 

 laws which cannot be tolerated long without leading to patho- 

 genesis. If a morbid tendency has been permitted to get a 

 firm footing, elimination in one shape or form has to set in, 

 and whilst one class of pathogenetic organisms is thus being 

 eliminated, the wholesome symbiogenetic union of strenuous 

 organisms is going forward all the time. Initial contrasts 

 there may be in abundance, but, as we have seen, they cannot 

 all continue indefinitely, and an increasing biological 



