LEE BARKER WALTON 117 



or conjugating organisms, although two exceptions, No. 

 12 and No. 14, are presented. An interesting fact, al- 

 though possibly only a coincidence, is that cross bred 

 zygospores of Spirogyra and of conjugating Paramecium 

 have approximately only one half the correlation ex- 

 hibited by close bred zygospores of Spirogyra and by non- 

 conjugating Parameciufn. 



The explanation of the conclusion here reached, that 

 the value of a character ""V in cross-bred forms does 

 not have the same tendency to change that the value of a 

 related character ^^y" has in close-bred forms, apparently 

 rests on a Mendelian basis. Its importance in evolution, 

 beyond the idea that more pronounced temporary com- 

 binations are thus allowed in the trial and error plan of 

 nature, is conjectural. 



4. Amphimixis and Death 



With the assumption that the results obtained in the 

 preceding investigation, together with the data presented 

 by other writers, when correctly analyzed, strongly sup- 

 ports the view that asexually produced organisms tend to 

 be more variable than those produced by the union of two 

 gametes, there is furnished evidence for the interpreta- 

 tion of the origin of sex — amphimixis and also for the 

 origin of death that would seem to rest upon a much more 

 secure basis than the purely speculative theories of Weis- 

 mann, Nageli, Hatscheck, Metschnikoff, Minot, etc., 

 which have previously been advanced. 



The chief advantage gained in the reduction of varia- 

 bility, while somewhat conjectural, would appear to be 

 that of holding organisms within limited bounds, or in 

 other words, asexually produced organisms in general 

 tend by their variability to exceed the limits of their 

 environment and thus perish, luhile organisms produced 

 by the mingling of two diverse lines of germ plasm with 

 their lessened variability m,eet the conditions of the com- 

 paratively slowly changing environment and their race 

 persists. This idea was proposed entirely upon specula- 

 tive grounds by Hatscheck ('87) who suggested that 



