174 J- H - HEWITT. 



THE OCCURRENCE OF ANIMALS CONTAINING BUT ONE 



MACRONUCLEUS. 



On four occasions animals from the stock cultures and from 

 the cultures of the control strains when killed and stained were 

 found to possess but one macronucleus and sometimes one and 

 sometimes two micronuclei. These animals were all large slow 

 swimmers or crawlers, and were selected because experience had 

 taught that these were the animals that showed early stages of 

 division, which were being sought at that time. 



Among the descendants of merozoon c, experiment 24, a 

 uninucleate animal with two micronuclei was found. The 

 original merozoon was from an animal cut during division. 

 From this it was thought that perhaps injury to the cell during 

 division might be the cause of this occurrence, but out of a 

 large number of animals out of this strain and other strains 

 derived from animals cut during division no other animals with 

 a single macronucleus were found. 



In experiment 76 a large slow crawler, evidently near division, 

 was cut anteriorly at 12 :25 P.M., August 9. The anterior mero- 

 zoon disintegrated immediately, the posterior merozoon increased 

 its activity. It was isolated into a clean glass capsule with five 

 drops of tap water and one drop of hay infusion. On August 10, 

 10:15 A.M., there was found in the capsule three animals, two 

 small and of the same size and a single large animal. The inter- 

 pretation made of this was that the merozoon had regenerated, 

 divided once into two individuals and that one of the latter had 

 again divided while the other was now approaching division. 

 On killing and staining all three of these animals it was found 

 that each of the small animals had two macronuclei and two 

 micronuclei, but the large animal had only one macronucleus 

 and two micronuclei. The macronucleus appeared about to 



divide. 



DISCUSSION. 



Since uninucleate forms occur both among the stock cultures, 

 the control strains and among the merozoa, a conservative infer- 

 ence must be that they are normal variations of this animal, 

 possibly brought about by its being adapted to laboratory media. 

 The relation between the two may be somewhat analogous to 



