REPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 65 



conjugating pair shortly after the union has occurred. In figure 

 10 the micronuclei have reached their maximum enlargement and 

 are shown in the spindle stage of the first division. In the animal 

 to the right, the micronuclei are in the same stage but are out of 

 focus. In figure 11, in the animal to the right what is interpreted 

 as the copulation nucleus can be seen in the spindle stage prior to 

 the first division. The same stage is present in the other animal 

 but it is out of focus. Figure 12 is in a stage just previous to the 

 separation of the gametes. 



The evidence presented both by the study of the living conju- 

 gants and the prepared material gives every indication that the 

 conjugation which occurred in the beef cultures was a normal proc- 

 ess and resulted in two ex-conjugants which, at the time of sepa- 

 ration, gave every promise of continued existence. 



VI. MORPHOLOGY AND PHYSIOLOGY OF THE EX-CONJUGANTS 



A. Living material 



Resulting from the 125 pairs of conjugants isolated during the 

 two epidemics, approximately 230 ex-conjugants were obtained 

 which appeared to be normal at the time of separation. Shortly 

 after separation they were quite as active as the regular non-con- 

 jugants of the cultures. They were a trifle smaller in size than the 

 average individual but extensive study of the living material failed 

 to show any other distinguishing characteristic. 



When examined a few hours later, the ex-conjugants invariably 

 showed that certain changes had taken place which may be sum- 

 marized as follows: (a) A noticeable decrease in size had occurred. 

 (b) The animals were considerably less active than formerly, (c) 

 The characteristic avoiding reaction had almost entirely disappear- 

 ed and their swimming movements consisted chiefly in turning on 

 their short axis, (d) A change in the shape of the ex-conjugants 

 had taken place and instead of having a normal elongated form, 

 they were very nearly circular, (e) The animals had become quite 

 dark in color. 



If examined again, some eight or ten hours later, a considerable 

 accentuation of these degeneration changes could be noted; again 



