186 BRITISH CICADiE. 



The proximate causes of variation are within the 

 powers of scientific investigation, and perhaps also of 

 solution ; but the ultimate cause must be beyond the 

 scope of finite reasoning. Science is engaged in 

 thrusting back, as far as possible, the final but neces- 

 sary resort to the act of a primus motor. 



The pilot of the steamship in the storm battles first 

 with the sea waves, and only in a secondary manner 

 does he regard the wind, which has caused the up- 

 heaval of water. But in quiet he may reflect on the 

 sources of wind, and consider the different densities of 

 air over large regions, which initiate the cyclone. 

 Pushing thought farther back, he may refer to the 

 powers of the sun, and finally to cosmic forces, what- 

 ever they may be. Kecognizing our limited capacities, 

 here we reverently rest, and consistently refer all 

 beyond to the will of the one Causa causarum. 



Many may regard rest as the final or normal con- 

 dition of matter, and say that nothing moves except 

 through the agency of force or forces appUed. Yet w^e 

 may equally well assume motion or life to be the ruliug 

 condition of things, and that rest in the universe is 

 abnormal. Thus we can take exception to the old poet's 

 dictum that — 



" Death is king of all." 



Life acting with or against purely chemical forces, 

 may be regarded as synthetic, and its agency on 

 organisms as modifying, restoring, and even preventing 

 the ordinary changes called decay, which may be con- 

 sidered as an analytical process. 



Biological variation may thus be approximately de- 

 fined, but not explained, as the result of the action 

 of life on the delicately balanced forces of very complex 

 organisms, whose parts are retained in unstable equi- 

 librium. This action is concerned in selectins: con- 

 ditions favourable to growth, in repelling those tending 

 to chemical decay; and in the unconscious choice 

 and adaptation of parts for producing and perfecting 



