LEE BARKER WALTON 129 



increases variability witli the assumption that variations 

 thus assumed to be produced are inherited in a cumulative 

 manner. The evidence, however, available at present, 

 supports a view directly contrary to this, namely that the 

 gametic condition makes evolution slower by decreasing 

 the diversity of available forms. Mendelian combinations 

 — amphimutations — may occur but the result is a decrease 

 in variability when the parental populations are compared 

 with the F2 or with a succeeding generation. The amphi- 

 mutations are transitory and there is no evidence that they 

 present anything actually new in themselves. 



Regardless of the opinions here at variance some of 

 which can only be established as sound generalizations 

 through long experimental investigation, the summary of 

 gametogenesis by Professor Coulter will be read with profit 

 and pleasure by those interested in problems of evolution 

 as well as by those particularly concerned with plant mor- 

 phology and development. 



