PERIODIC REORGANIZATION IN PARAMAECIUM 435 



work proceeded and consequently the study was concentrated 

 particularly on one (VI) of the six lines — the other lines being 

 merely controlled to show the occurrence of the process, at which 

 time all the cells available from these lines were also preserved. 

 In many cases all the animals of certain lines were killed in the 

 reorganization process so that every animal could be studied. 

 The places of these lines were supplied by new ones from one of 

 the remaining five lines. Thus by killing of various lines and 

 the branching of others to take their places a total of fifteen 

 sub-lines of longer or shorter duration were formed. These to- 

 gether with the six original lines made a total of twenty-one lines 

 whose cytology was investigated.- 



The individual animals were fixed in Schaudinn's sublimate- 

 alcohol (stronger solution), stained with Delafield's hematoxylin 

 and mounted in cedar oil — the specimen being watched under a 

 Zeiss binocular microscope throughout the operations, and trans- 

 ferred with a capillary pipet from one depression slide to another as 

 occasion demanded. Differentiation was effected with acidulated 

 alcohol (70 per cent alcohol + 0.002 per cent HCl) under a com- 

 pound microscope. The following staining reagents were tried but 

 the above methods gave the best results — bearing in mind that 

 each animal had to be carried along under constant observation 

 through each of the fluids until it was in the cedar oil under a 

 coverglass: Heidenhain's hematoxylin and Bordeaux red, methyl 

 green andeosin; Delafield's hematoxylin and eosin; safranin and 

 methyl green ; Mannsche Farbung and Giemsa f eucht. Animals 

 preserved in bulk from mass cultures were submitted to the same 

 staining methods and again Delafield and eosin were found most 

 satisfactory; Heidenhain staining the trichocysts too greatly. 

 Sections (5/i) were made of animals in various stages of the proc- 

 ess but they did not afford important details which could not be 

 made out in the total mounts. The sections were stained with 

 safranin and Heidenhain according to the suggestions of En- 

 riques ('12). 



- After the definitive experiments were formally concluded at the end of six 

 months, certain lines were continued to June 14, 1914, in order to secure some 

 further details. 



