178 Evolution Not Accidental 



his theory more than a hypothesis to explain what 

 we do not know to be a fact ? 



§18. Evolution Not a "Chapter of Accidents." 



It seems justifiable to say that the range of the for- 

 tuitous has shrunk since the early days of Darwinism. 

 As we have seen, when Darwin called variations or 

 new departures "fortuitous," he meant little more 

 than to acknowledge that they arose from conditions 

 too complex for his analysis. We know that some 

 variations arise from what might be called a shuffling 

 of the hereditary cards contained in the chromo- 

 somes of the germ-cells, and there is in this a certain 

 fortuitousness. It appears to be by a chance distribu- 

 tion that some of the chromosomes in the nucleus of 

 the egg-cell are removed in the first polar body. On 

 the other hand the permutations and combinations of 

 hereditary factors that result in new patterns must 

 be in some measure congruent with the already estab- 

 lished architecture. "Anyhow variations" cannot take 

 hold, and this is one of the reasons why constitutional 

 diseases so rarely show face in Wild Nature. They 

 are incongruities, and it seems to be a fact not only 

 that they are prevented by selection from taking 

 root, but also that they very seldom occur. When 

 variations are definite or orthogenic — that is to say, 

 additions to or subtractions from previously existing 

 steps of change — they are obviously far removed 

 from the fortuitous. We have admitted our ignorance 

 of the origin of mutations or brusque qualitative new 

 departures, like a calculating boy or a musical genius 



