EFFECT OF CONJUGATION 351 



In some cases a line begins with a high rate of fission, then runs 

 down to a verj^ low one, dividing but once or not at all during 

 the last six-day period. Such is the case, for example, in the 

 lines deri\'ed from pair 4. In such cases careful and extended 

 tests were made to determine whether the slow fission rate was 

 characteristic of all the members of the given line. Thus, of 

 line 4: ax, seven sets; of 4: ay, nine, and of 4:bx, eight sets; were 

 kept in progress during the last twelve days of the experi- 

 ment; all showed the same extremely low rate of fission charac- 

 teristic for the fines derived from pair 4 in tables 34 an,d 24. 



In the same way, eleven sets of No. 5 a, eight of No. 5 b, 

 twenty sets of No. 6 h, six sets of No. 26 a, and eight sets of 

 No. 15 6 were kept in progress during the last twelve days of the 

 experiment; all of them showed slow rates of fission corresponding 

 closely to those given for the lines in question in table 34. 



Of the rapid fines, No. 9 a was tested by keeping eighteen 

 parallel lines in progress during the last twelve days of the experi- 

 ment. All divided rapidly, giving 18 to 20 fissions during the 

 twelve days. 



It is thus clear that the lines descended from the ex-co?ijugants 

 are differentiated in their inherited characteristics, some having a 

 rapid rate of fission, some a slow rate, and some an intermediate 

 one (although all were kept under absolutely identical conditions) . 

 One result of this inherited differentiation is the production of the 

 very high coefficients of variation shown in table 23. 



Are there likewise inherited differentiations among the lines 

 derived from the non-conjugants — ^the members of the split pairs? 

 Examination of the coefficients of variation in table 23, as 

 well as a general inspection of table 35, shows at once that if 

 there is any such differentiation, it is very slight compared with 

 that among the descendants of the conjugants. If we compare 

 very carefully the records of the different lines in table 35, we 

 find a few cases in which it is doubtful whether there may not be 

 inherited differentiation. Line 3 ax, for example, shows a rate 

 of fission somewhat below that of most others, while 6 by, 22 ax 

 40 ay and 44 ax show rates rather above the average. But the 

 differences between even the extreme cases are very small com- 



