No. 5S7] VARIABILITY AND AMPHIMIXIS 679 



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, while organisms produced 

 by the mingling of two diverse lines of germ plasm with 

 their lessened variability meet 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 

 variation would run riot if not controlled by the union of 

 germ cells, and it would now appear that the facts sup- 

 port such a proposition. "While it has been suggested 

 that the chief function of amphimixis was that of re- 

 juvenation, a consideration of the discussion on "Com- 

 parative Size" as well as the recent experimental results 

 obtained in the production of Paramecium do not support 

 such an opinion to the exclusion of the hypothesis here 

 put forward. East and Hayes ('12) have advanced the 

 theory that recombinations in accordance with Mendelian 

 principles were the chief purpose of amphimixis. "While 

 new combinations are thus brought about, apparently 

 there exists a real difficulty in understanding how transi- 

 tory heterozygotic forms could become of selective value 

 in originating and maintaining such a process. 



The acceptance of the conclusion that asexually pro- 

 duced organisms are more variable than those produced 

 by amphimixis, and that thus some of the units are more 

 readily subject to the eliminating influences of the en- 

 vironment, affords a comparatively simple explanation 

 of the origin of death in multicellular forms which are 

 built up of such units — the cell. Consequently the infer- 

 ence is that 4 death occurs as the result of the continually 

 forming body cells becoming so variable through the 

 absence of control by amphimixis, that eventually some 

 one group fails to meet the limits imposed by the environ- 

 ment, and these together with the remainder of the colony 



* Walton, Science, p. 216, 1909. 



