I2O BRUCE D. REYNOLDS. 



actions persisted until the I5th (j-i6 and j-s-i6); this was 

 followed by a brief period of cross-fusion, after which the inter- 

 actions became permanently negative number of observations 

 in this case was 35. 



A similar series of experiments between lines n and n-su of 

 clone N were started on August 2yth. In this case line n-su was 

 removed from the sugar solution before the negative condition 

 had been attained; consequently cross-fusion continued until 

 the 1 5th day. From this time on all of the interactions were 

 negative. Forty observations were made in this series of experi- 

 ments. 



(c) 10 Per Cent. Hay Infusion Containing N/io Saline. 



Two series of experiments were conducted in which one line of a 

 clone was placed in a culture medium of 10 per cent, hay infusion 

 plus one tenth normal saline solution, while the other line was 

 kept in the standard medium the only difference between the 

 environments of the two lines was that the culture medium used 

 for one contained 0.09 per cent. salt. During the first three days 

 the organisms in the saline solution seemed to grow and repro- 

 duce normally; after this, three days elapsed before another 

 division occurred ; then further growth ceased. In the meantime 

 tests showed that cross-fusion between the two lines took place 

 readily. After keeping the organisms in saline solution for eight 

 days they were put back into standard culture medium. The 

 interactions continued to be positive for two more days, then the 

 experiments were discontinued. 



The evidence obtained from these observations indicates that 

 N/io saline is an unfavorable environment for A. polypora; but 

 regardless of this, no physiological change that can be detected 

 by the cross-fusion method was thus produced. 



10 Per Cent. Hay Infusion Containing Acetic Acid. 

 Numerous attempts were made to culture the organisms in 10 

 per cent, hay infusion to which had been added various amounts 

 of acetic acid, but after repeated efforts it was found impossible 

 to keep the animals alive in solutions containing only o.oi per 

 cent, acetic acid. Other acids, or weaker concentrations of 

 acetic acid, were not tried. 



