292 H. S. JENNINGS 



hand, the upper extreme for the non-conjugants (38) is higher 

 than that for the conjugants (32), but most of the non-conjugants 

 are so grouped near the high figure that the variation is relatively 

 small. 



Mortality. None of the 59 lines of non-conjugants died out 

 during the five weeks of the experiment. Of the 61 lines of 

 conjugants, on the other hand, 23, or 37.7 per cent, died out 

 during the experiment. The number of lines descended from 

 conjugants that died out during each week is given in table 5. 



Thus in this case conjugation greatly increased the mortality. 

 Although the 'spht pairs' were ready to conjugate, and had 

 actually taken the first steps in the process, they are not in the 

 least injured by being prevented from consummating the process; 

 while those that finished mating showed a high mortality. 



Abnormalities. Besides the actual deaths, the descendants of 

 those that had conjugated showed many abnormalities, while 

 among the descendants of the non-conjugants there were none. 

 For example, on May 14, I noted that there were among the 

 descendants of the conjugants 24 abnormal individuals, belonging 

 to 12 different lines, while in the other set there were none. 



The abnormalities take the most diverse forms: bodies of 

 irregular shape, crooked, truncate, or with projections; double or 

 multiple monsters: some are abnormally large, others extremely 

 thin. The structural abnormalities are in many cases connected 

 with abnormalities in fission. In some cases the ex-conjugants 

 do not divide for many days after separation. During this time 

 they grow larger till they reach an immense size, many times 

 greater than that ever reached at other times. Some of these 

 immensely large individuals nev-er divide again, and after living 

 a week or two die. Others after a time divide irregularly, pro- 

 ducing progeny of diverse sizes and forms. Thus the individual 

 10a, of the pairs, in this experiment did not divide until eight 

 days after the separation from its mate. It then divided during 

 the night into seven, of four diverse sizes. The individual 176 

 divided immediately into two specimens, which became im- 

 mensely large; these did not divide again for six days, then each 

 produced two large abnormal individuals which soon died. 



