80 Regulation of Size in Unicellular Organisms 



sters during subsequent regeneration. The forms of 

 these monsters, in Stentor and in Paramecium, indi- 

 cated that they were truly multiple animals; they had 

 grown, but their protoplasms failed to separate. Some 

 of the monsters contained single unusually large nu- 

 clei ; others contained a separate nucleus and other dis- 

 tinct structures, for each of the individuals represen- 

 ted in the incomplete fissions. Balbiani ('93) also 

 found that normal single individuals were given off* by 

 regular fission from one or another of the cohering 

 "individuals" of Paramecium. 



The two species used by Balbiani have yielded the 

 most extensive results in subsequent cutting experi- 

 ments. In Stentor incomplete and irregular fissions 

 were observed to occur by Johnson ('93), Prowazek 

 ('04a) and Stolte ('22). Irregular fissions were simi- 

 larly observed in Paramecium by Lewin ('11), Calkins 

 ('lib), and Peebles ('12). But in all these cases the 

 abnormally formed or sized Stentors or Paramecia 

 either die or within a few generations regulate back to 

 normal, and not only in cytoplasmic structure but also 

 in nuclear form and size. 



In another ciliate, Stylonychia, monstrous forms re- 

 sulted after cutting (Prowazek, '04b); but these indi- 

 viduals were not observed to undergo further fission- 

 ing. 



Under chemical influences. Prowazek ('08) inves- 

 tigated the influences of some chemical substances 

 upon fission in Trypanosoma equinum. He found that 

 extremely dilute hydrochloric acid depressed cytoplas- 

 mic division while nuclear division went on, and big in- 

 dividuals were thus obtainable. In no cases, appar- 

 ently, was Prowazek ('10) successful in hastening fis- 

 sion in Colpidium by means of chemical substances. 



Crampton ('12) noted that Paramecia and Stylony- 

 chiae which were confined in narrow glass tubes failed 



