VARIABILITY AXD AMPHIMIXIS 



made, upon analysis support the direct conclusions which 

 follow. 



It may be objected that cells of mature filaments 

 originating from the zygospores should have been studied. 

 While this would have been of interest, the zygospores 

 themselves are individuals in the cycle of development, 

 and the differences as represented in the groups chosen 

 can not be said to have less value than data from another 

 part of the life cycle. 



The possibility of the results being affected by the 

 swelling of zygospores due to the 2 per cent, formalin 

 used in preservation, became apparent when other duties 

 prevented measurements within the anticipated time. 

 The first series of 358 zygospores was measured between 

 April 2 and May 16, while the remaining 42 were meas- 

 ured between August 17 and 21. The question seemed 

 an important one, and in order to test the extent of such 

 an error if present, the average diameter of the last lot 

 was compared with that of the first lot, the values being 

 29.15 m. and 29.08 m., the difference of 0.07 m. being well 

 within the limits of the probable error. The 42 zygo- 

 spores measured August 17-21 happened to consist of an 

 equal number of lateral and soalariform individuals, 

 which would thus tend to eliminate an error should it 

 have occurred. Consequently the use of the formalin 

 does not appear to have affected the results. 



Some evidence has been presented that new phylo- 

 genetic characters are more variable than older char- 

 acters. Thus if lateral conjugation was a recent acquisi- 

 tion the greater variabitiy might have been expected. 

 Pearl and Clawson ('07) found a higher variation in the 

 great chela of the crayfish, Camburus propinquus Girard, 

 than in the protopodites of the 2 and 3 legs, nevertheless 

 they preferred to attribute the result to ontogenetic 

 rather than to phylogenetic factors. MacDougall, Yail 

 and Shull ( '07) stated that 



the greater variability nf pliyln-cno! ically now characters as compared 



