128 BRUCE D. REYNOLDS. 



to a common state; (6) by transferring medium only from one 

 line to the other thus making the conditions in the latter like 

 those in the former; (c) the environments of both lines were 

 changed through the use of a different culture medium; these 

 were then brought to a common identity by exchanging small 

 quantities of culture medium between them. 



Members from the Petri dish cultures of clones J and K were 

 used for this purpose. When tested on August 25 it was found 

 that the two lines of these clones reacted negatively towards each 

 other's fragments. By estimating the number of individuals in 

 each Petri dish, and knowing the number of days the cultures had 

 been running and their usual rate of reproduction, a fairly accu- 

 rate determination could be made of the number of generations 

 represented in each line. In every case the number used was 

 slightly under the estimated number. By following this pro- 

 cedure the figure obtained on August 25 were: for clone J, line 

 j-66 generations and line jd-6o; for clone K, line k-yo and line 

 kd 68. The same day three types of experiments were begun 

 in which both of these clones were used. 



(a) Two small drops of culture media were interchanged be- 

 tween the old receptacles containing specimens from one line 

 and the new concavities into which a specimen from the other 

 line was to be placed each time the organisms were conveyed to 

 fresh cultures (every two days). At intervals of two or three 

 days observations were made of the reactions between individuals 

 from the two lines. In clone J the interactions of lines j and jd 

 continued to be of the shattering type for 18 days (until Septem- 

 ber 12), when cross-fusion was exhibited (line j-84 and line jd- 

 s<. l-'rnm this time until the experiments were discontinued on 

 November I ( j-124 and jd-i 19), individuals from one line would 

 readily fuse with fragments that had been severed from members 

 of a sister line. In clone K the interactions between lines k and 

 kd were of the shattering type for 20 days (until September 14). 

 From this time on, cross-fusion between the two lines was exhib- 

 ited, though several shattering reactions were also observed. 

 The experiment was discontinued on November i, at which time 

 line k had undergone 135, and line kd 132 divisions since clone K 

 was started on June 25. 



In the following experiments attempts were made to bring 



