no THE SHORTER SCIENTIFIC PAPERS 



those produced by lateral conjugation, loses its force. 

 Furthermore it is believed that all investigations thus far 

 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 

 29.1 5 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 scalariform 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 characters. 

 Thus if lateral conjugation was a recent acquisition the 

 greater variability might have been expected. Pearl and 

 Clawson ('07) found a higher variation in the great 

 chela of the crayfish, Cambunis 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, Vail and 

 Shull ('07) stated that 



the greater variability of phylogenetically new characters as compared 

 with older ones ... is confirmed . . . (p. 89). 



