684 GARY N. CALKINS 



for example, isolated 132 pairs of closely related conjugating 

 Stylonychia pustulata: "None of these ex-conjugants divided and 

 none lived forty-eight hours after separating." 



Two hundred pairs of conjugating Blepharisma undulans 

 have been isolated and followed in culture after conjugation. 

 The observations were made at different times during the year, 

 to allow for possible seasonal predilection. The results have 

 confirmed Biitschli's observations in every respect. Not a 

 single ex-conjugant divided and the majority died within ten 

 days; two, only, dragged out a miserable, weakened existence 

 for twenty days. They become smaller and more vacuolated, 

 until finally they bear little resemblance to the original robust 

 forms from which they came (figs. 10, 11, 23). 



If this negative result were common to all ciliates in culture 

 there might be a more reasonable chance of interpreting con- 

 jugation. But this is not the case, nor is it common even 

 amongst paedogamous ex-conjugants. Paramecium, Colpidium, 

 Gastrostyla, Euplotes, Vorticella, Didinium, and a score of 

 other ciliates have been cultivated after conjugation. Stjdo- 

 nychia, wdth Maupus, continued to live. Death after conjugation, 

 therefore, seems to be rather an exception than a rule. 



There is reason to believe that failure to live after conju- 

 gation is due to the conditions in the laboratory cultures. We 

 have found, for example, that while ex-conjugants of Parame- 

 cium caudatum, from natural ponds or other external sources, 

 continued to live in the proportion of from 70 to 80 per cent, 

 those derived from prolonged cultures continued to live in the 

 proportion of only 6 per cent (Calkins '03, Cull '07). The 

 reason for this discrepancy must be sought in the conditions 

 under which conjugation occurred. So, too, it is probable that 

 the failure of Blepharisma to live after conjugation is due to 

 some imperfection in the cultural conditions in the laboratory. 

 Here the 'infant mortality' is 100 per cent, but in Paramecium 

 caudatum under culture, the infant mortality was 94 per cent, 

 almost as bad, while under conditions more nearly like those 

 in nature the rate fell to 30 or 20 per cent. The theoretical 

 interest centers in the 6 per cent of the culture Paramecium 



