216 Life and Death, Heredity and Evolution 



bines this idea with the theory that these disintegrating 

 variations follow a definite course, predetermined in large 

 measure by the constitution of the disintegrating material. 



There are two points that need consideration in dealing 

 with this theory. The first is one of observational fact ; al- 

 though it is true that many mutations appear to be cases of 

 loss and disintegration, yet there is no indication that this 

 is the case in such results of selection as have been described 

 in the Protozoa ; heritable variations are not limited to any 

 particular direction. 



But secondly, it appears to me that this conclusion that 

 evolution is by disintegration and loss is based on an error 

 in logic, which, being detected, puts it out of consideration. 

 As we examine the series of organisms, from amoeba to man ; 

 or as we examine the palaeontological series, we find a grada- 

 tion from those showing little visible differentiation to those 

 showing great visible differentiation; the problem of evolu- 

 tion is as to how the passage was made from those visibly 

 little differentiated to those visibly highly differentiated. 



But now, according to the doctrine we are considering, 

 when we come to examine the actual changes in hereditary 

 characters, we detect on the whole only the disintegration 

 of organisms already visibly differentiated ; only a change 

 from greater visible differentiation to less. 



The doctrine then proceeds to draw from this fact the 

 absurd conclusion that the visibly more differentiated must 

 have arisen from the visibly less differentiated by decrease 

 in the differentiation of the latter ! 



So preposterous a conclusion can be drawn only from the 

 fact that while in our premises we are talking of visible in- 

 crease and decrease of differentiation, in the conclusion as 

 ordinarily drawn the ground is shifted to mean something 

 entirely different, an inner, invisible, purely theoretical 



