Life and Death, Heredity and Evolution 



After the union of the two half nuclei the two mates sep- 

 arate; we may now call each an ex-conjugant. Now a set of 

 peculiar processes occurs, with the result of restoring, 

 through two divisions of each ex-conjugant, individuals hav- 

 ing the same structure as did the mates before conjugation. 

 Some of the details of the process may turn out of great 

 significance, though at present their meaning is not clear. 



At separation each ex-conjugant has a single nucleus 

 formed by the union of the two half nuclei (Figure 30, F). 

 This single nucleus divides, producing two ; these divide, pro- 

 ducing four; these again divide, producing eight. These 

 eight are all present in the single ex-conjugant (Figure 

 30, J). Now of these eight three dissolve and disappear, 

 leaving five in the single individual. One of these, as it 

 later turns out, is the nucleus from which all the micronuclei 

 of later generations arise by division; the other four later 

 form four macronuclei of four individuals of later genera- 

 tions, each increasing greatly in size. 



Now the single ex-conjugant divides, producing two indi- 

 viduals. At the same time the single micronucleus divides 

 into two halves, each passing to one of the offspring. Each 

 of the two offspring also receives two of the four macronu- 

 clei, which are now enlarging (Figure 30, K). Next each 

 of these two offspring divides anew with repetition of the 

 division of the micronucleus, while of the four progeny each 

 receives one of the four macronuclei. Thus after two divi- 

 sions of the ex-conjugant, offspring are produced with a sin- 

 gle macronucleus and a single micronucleus (Figure 30, L), 

 like the individuals before conjugation. Each of the four 

 individuals arising from an ex-conjugant has one of the 

 four macronuclei that were present in the ex-conjugant. 

 But the micronucleus of each of the four is derived by divi- 

 sion from a single micronucleus present in the ex-conjugant. 



