PLATE 1 



EXPLANATION OF FIGURES 



These photographs were taken from permanent preparations stained with 

 picrocarmin. The same magnification (600 diameters) was used in all eases and, 

 therefore, the relative sizes represent absolute differences in the size of the dif- 

 ferent individuals. 



Oxytricha fallax 



1 A typical normal individual taken from the Oh culture at the beginning 

 of the work. One of the micronuclei has divided prior to cell division. 



2 to 4 In these figures are to be seen types of the abnormal animals which 

 appeared later in the history of the cultures. Figure 2 was taken from the Ove 

 culture, December 12, 1911, at the 110th generation. Figure 3 was taken frqm 

 the Oh culture January 27, 1912, at the 158th generation. Figure 4 was taken 

 from the Ob culture January 27, 1912, at the 121st generation. 



5 A typical normal individual taken from the Obtt culture on February 15, 

 1912, several days after the death of the last of the daily isolation cultures. 



6 An atypical individual taken from the Obtt culture on May 18, 1912, about 

 two weeks before this culture died out. 



Pleurotricha lanceolata 



7 A typical normal individual taken from the Ph culture at the beginning of 

 the work. 



8 An atypical individual taken from the Ph culture August 28, 1912, at 

 the 637th generation. This culture died out four weeks later. 



9 An atypical individual taken from the Pb culture August 28, 1912, at the 

 597th generation. 



10 A normal individual taken from the Phtt culture September 7, 1912. 



11 A normal individual taken from the Phtt culture October 20, 1913. 



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