118 THE SHORTER SCIENTIFIC PAPERS 



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^ death occurs as the result of the continually 

 fomting body cells becoming so variable through the 

 absence of control by amphimixis, that eventually some 

 one group fails to m^eet the limits imposed by the environ- 

 ment, and these together with the reTnainder of the colony 

 — the individual — perish. The experiments of Wood- 

 ruff ('11, etc.) who in extending the work of Maupas and 

 of Calkins was able to rear several thousand generations 

 of Vara^necium without conjugation, as well as the in- 

 vestigations of Harrison subsequently elaborated by 

 Carrel, where human and other animal tissues main- 

 tained cell division for a prolonged time in an artificial 

 medium, are here of much interest. In each case the 

 result is brought about by the favorable artificial environ- 

 ment, and it is made more clear that death itself is wholly 

 or in part due to the unfavorable conditions surrounding 

 an organism. 



^Walton, Science, p. 93 5, 1912. 



