Process of Evolution 217 



kind of disintegration and differentiation. If we recall that 

 we were dealing in the premises with visible increase and de- 

 crease of differentiation, and that therefore in the conclusion 

 we must deal with the same, the absurdity of the conclusion 

 becomes manifest. All that we can legitimately conclude, 

 if we accept the premise that the observed changes in hered- 

 itary characters are cases of loss and disintegration, is that 

 we have not seen the process of evolution occurring. But 

 we are not compelled to accept that premise. In the lower 

 organisms at least it cannot be asserted that all changes of 

 hereditary characters are cases of loss and disintegration. 



General View of the Processes and Problems of Development, 



Mating and Evolution, in the Light of What We 



Find in Lower Organisms 



Let us now attempt an outline of what our examination of 

 the processes of mating and development have shown us in 

 the lower organisms, in so far as it agrees with what we find 

 also in the higher organisms. 



We saw at the beginning that each species of organism, 

 so far as studied, is differentiated into many slightly diverse 

 stocks, each diversity hereditary. This we found to be true 

 both in Protozoa and in higher organisms. We saw, too, 

 that in simple reproduction from a single parent, by division 

 of a cell or of an individual, there is a high degree of con- 

 stancy in the hereditary characters of these slightly differ- 

 ing stocks. The constancy is so great that for a long time 

 the search for hereditary changes was at a standstill; the 

 stocks seemed permanent. 



But with intensified study, it was found that in the 

 Protozoa changes in the hereditary characters do occur 

 even in reproduction by simple division. Such an organism 

 as Difflugia gradually differentiates, even without mating, 



