THE VARIABILITY OF ZYGOSPORES IN SPIKO- 

 GYRA QUADKATA (HASS.) FORMED BY 

 SCALARIFORM AND BY LATERAL 

 CONJUGATION, AND ITS BEAR- 

 ING ON THE THEORY OF 

 AMPHIMIXIS''- 



With the object in view of obtaining data bearing up- 

 on the purpose of amphimixis, and the causes tending to 

 produce variability — problems which have long remained 

 most elusive in everything except theory — a biometrical 

 investigation in respect to the comparative variability and 

 correlation in 400 zygospores of Spirogyra quadrat a 

 (Hass.) formed by scalariform and by lateral conjunction 

 was undertaken. 



In the first instance (scalariform conjugation) we deal 

 with the results of conjugation between remotely related 

 cells belonging to different filaments. In the second in- 

 stance (lateral conjugation) we deal with the results of 

 conjugation between sister or adjacent cells of the same 

 filament, a condition closely related to the phenomena of 

 parthenogenesis in other organisms. If the conjugation 

 of germ cells from remotely related individuals tends to 

 variability as Weismann and others would have us believe, 

 conversely the union of closely related cells should afford 

 a decreased variability, the minimum appearing in parth- 

 enogenetic forms. 



The results show a condition directly contrary to this, 

 the zygospores of lateral conjugation being approximately 

 21 per cent more variable in length and 31 per cent more 

 variable in diameter than those produced by scalariform 

 conjugation. Consequently, direct evidence is afforded 



'•Reprinted from Science, N. S., vol. 27 (1908), p. 907. 



