AMPHIMIXIS, VARIABILITY AND DEATH; SOME 

 FACTS AND A THEORY==- 



In connection with some studies on the variabihty of 

 zygospores in Spirogyra in flat a (Vauch.) formed by scal- 

 ariform (amphimixis) and by lateral (quasi partheno- 

 genesis) conjugation, certain facts are presented which 

 allow an interpretation of the cause of death among 

 organisms from a different standpoint than the generally 

 accepted theory. 



In 200 zygospores produced through the conjugation of 

 cells of different filaments — sexual reproduction — the co- 

 efficient of variation is 9.5093 for length and 5.7471 for 

 diameter. In the same number of zygospores produced 

 by the fusion of adjacent cells of the same filament — 

 comparable to asexual reproduction — the coefficient of 

 variation is 11.9364 for length and 7.5376 for diameter, 

 indicating for the given conditions that the cross-bred or 

 sexually-produced zygospores, in themselves the young 

 individuals from which the mature filaments arise, are 

 relatively 20 per cent less variable in length and 23 per 

 cent less variable in diameter. 



Thus if amphimixis decreases variability, there is pre- 

 sented an interesting condition bearing not only on the 

 problem of the origin of sex, but also on the origin of 

 death, for the theory is equally applicable to the individ- 

 ual cell, whether isolated, as in the Protista, or associated 

 in colonies, as in the higher animals and plants. The 

 development of the body in multicellular organisms rep- 

 resents merely the development by asexual reproduction 

 of an infinite series of cell individuals. Consequently the 

 evidence suggests that death ocnirs 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 im- 



*Reprinted from Science, N. S., vol. 35 (1912), p. 935. 



