324 SEX IN MICROORGANISMS 



exposed independently to the action of a fluid agent which it does 

 not itself produce. Possibly a particular conjugation-inducing agent 

 activates animals which do not produce this agent. The substances 

 involved in the initial adhesion might well be formed as a result of 

 such activation. If these adhesive substances acted in non-specific 

 fashion, any two activated animals, regardless of mating type, should 

 adhere on contact and might then proceed to conjugate. The effect 

 of the fluid agents on Euplotes would then be roughly analogous to 

 the activating action of mating substance interaction in Paramecium. 

 Initial union (by ventral cirri. Turner, 1941) of Euplotes would then 

 correspond to holdfast union in Faraviec'mvi. Viewed in another way, 

 the conjugation-indulging agents in Euplotes are analogous in action 

 to the killer fluids which induce pairing and nuclear reorganizations 

 in Faramecium (see under parthenogenesis in Paramecium) . 



This view accounts for the failure to observe an immediate reac- 

 tion when fluids and animals or complementary types of Euplotes 

 are mixed. No effect is observed for at least 90 minutes. According 

 to the scheme this is the time required for synthesis of the "non- 

 specific adhesive substances." No mass mating reactions occur in mix- 

 tures of Euplotes mating types, and this also might be expected since 

 large numbers of animals would not necessarily be in the adhesive 

 stage simultaneously. In any event, mass agglutination of Euplotes 

 presents mechanical difficulties for the adhesive organelles (ventral 

 cirri) are present only on one side of the animal. The importance of 

 this factor may be seen in Kimball's (1941) observation that double 

 animals do form small groups or chains. 



It might be expected from this view that fluids would induce 

 other activation phenomena in responsive Euplotes in the absence of 

 conjugation. Such action has not been reported. In fact Kimball 

 (1941) describes exconjugants (probably animals from pairs split in 

 early conjugation stages) which failed to show any nuclear changes. 

 Similarly Katashima (1952) separated conjugating E. harpa by killing 

 one pair member and then studied the nuclear behavior of the surviv- 

 ing member. When the operation was performed after the "prelim- 

 inary micronuclear division" (2 to 5 hours after beginning of conju- 

 gation) but before the first meiotic division, the nuclear composition 

 of the surviving isolate promptly returned to the vegetative condition. 

 When the operation was performed at later stages, the micronuclei 

 sometimes completed the nuclear cycle (cytogamy). Clearly, then, 



