NO. 587] VARIABILITY AND AMPHIMIXIS 651 



the adjacent cells of a single filament unite to form the 

 zygospore, itself a young individual, and at the same time 

 by scalariform conjugation (Fig. 1, B) where the cells of 

 two distinct filaments unite to form the zygospore. Thus 



there is an example of a population producing under 

 the same environment two groups of individuals, one 

 by close breeding (lateral conjugation) and the other 

 by cross breeding (scalariform conjugation), and a com- 

 parison of the variability by statistical methods should 

 afford evidence toward the solution of the problem pre- 

 sented where the offspring have arisen from a common 

 ancestor as indicated in the material studied. 



2. Historical 



Much has been published concerning hybridization, 

 cross and close breeding, amphimixis and parthenogene- 

 sis, all of which are distinguishable from one another 

 merely by degree, nevertheless so far as the subject under 



