CONJUGATION IN BLEPHARISMA UNDULANS 683 



but a step in advance. The syncaryon of Blepharisma divides 

 twice before nuclear differentiation. In Paramecium it divides 

 three times. If the four nuclei of Blepharisma should divide 

 again, and by the division should separate tropho- from idio- 

 chromatin, the former then sweUing into macronuclei, the con- 

 ditions would be identical with those of Paramecium. 



Such an hypothesis of the origin of the dimorphic nuclei of 

 ciliates is much more plausible than one based upon hypothet- 

 ical binucleated ancestral forms. Metcalf ('09) for example, 

 has advanced an elaborate theory requiring a number of sup- 

 positions: first, a delay in the process of division, estabhshing 

 a temporary binucleated condition; second, a complete sup- 

 pression of the delayed division, making the binucleated con- 

 dition permanent; third, a shifting of division planes from 

 longitudinal to transverse. Not one of these suppositions has 

 sufficient evidence to warrant it. The facts indicate that the 

 macronucleus represents the trophochromatin contained in the 

 original syncaryon from which it is derived either by secretion, 

 as in Blepharisma, or by differentiating division, as in Paramecium 

 and its allies. No comphcated phylogenetic hypothesis is needed 

 in the fight of these. 



The second problem suggested by the history of Blepha- 

 risma undulans is the much discussed matter of conjugation and its 

 significance. The process and its sequences in Blepharisma throw 

 no new light on the subject but rather add to the perplexity 

 of the tangle by an additional difficulty, for conjugation in Ble- 

 pharisma under cultural conditions, is equivalent to a death warrant. 

 BiitschU (76) noted that ex-conjugants of Blepharisma lateritia 

 invariably die: ''Langer gelang es mir nun nicht die aus der 

 Conjugation hervorgegangenen Thiere lebend zu erhalten: schon 

 am zweiten Tage nach losung der Syzygie starben viele ab, 

 der Rest am dritten Tage" (p. 316). Nevertheless he made 

 no remark on this apparent exception to his theory of Ver- 

 jungung in explaining the significance of conjugation. Maupas, 

 likewise, observed fruitless conjugations, interpreting them as 

 due to close relationship. A few other observers have also called 

 attention to the invariable death of ex-conjugants. Baitsell ('11), 



