198 GEOLOGICAL BIOLOGY. 



ment of variation, is also a conspicuous fact in nature. To' 

 explain the origin of species involves the accounting for the 

 becoming fixed or permanent of variable elements of organi- 

 zation, as well as the accounting for the previous variability 

 of the characters now fixed. 



Darwin's theory and those like it are chiefly engaged in 

 accounting for the acquirement of permanency of originally 

 variable elements. The Lamarckians and Neolamarckians are 

 chiefly interested in accounting for the variability. While 

 natural selection is effective when the differences themselves 

 are already on hand, it assumes variability to be a fact without 

 explaining it. It is necessary to account for variation itself, 

 and those who assume, that any structural modification which 

 an organism may acquire during its lifetime may be trans 

 mitted to its offspring, necessarily emphasize the effects of use 

 and disuse, the retarding or accelerating of growth, and, in 

 general, all the factors of variation tending toward variation 

 of the individual during its life. 



It is in the field of observation rather than in speculation 

 that the solution of these questions is to be found. So soon 

 as we admit the possibility that the transmission of characters 

 from one generation to another may not be absolutely con- 

 stant, we throw back the whole discussion into the field of the 

 actual laws of progress in generation. If the organisms have 

 varying degrees of the growth-force, if they can in the least 

 degree choose for themselves the course of development of 

 their organization, the whole problem of evolution may be 

 accounted for by the operation of this force — a force which 

 then becomes the most important factor in the case. But 

 before we can reach a final theory of the origin of species 

 we need to know what the facts are. Hence it is that the 

 whole subject of variation, both in living forms and as ex- 

 pressed in the historical series, is of vital importance. Not 

 only is variation an intrinsic law of organic generation, but as 

 has been shown with overwhelming force, the discontinuity 

 which we observe separating the character of one species from 

 those of species next to it in likeness is not a result of natural 

 selection, " nor has it its origin in environment," " nor in any 

 phenomenon of adaptation, but it is in the intrinsic nature of 



