PHYSIOLOGICAL CHARACTERISTICS OF AXIATE PATTERNS 93 



ond region of higher susceptibility at the extreme posterior end in some, 

 not in all, individuals, perhaps associated with reconstitution after fission 

 or possibly with backward locomotion.' A characteristic effect of exposure 

 to ultra-violet radiation is shortening of the anterior region (Fig. 28, A-C) ; 

 with sufficient exposure this may be followed by complete cytolysis of the 



G 



H 



I 



Fig. 28, A-L. — Differential susceptibility of Paramecium. A-D, ultra-violet; E, F, HCl; 

 G, H, methylene blue, high concentration; /, /, neutral KCN; A', L, lack of oxygen (from Child 

 and Deviney, 1926). 



ectoplasm, progressing from the anterior end posteriorly (Fig. 28, D), or 

 with less intense effect by a similar gradient of loss of structure in the ecto- 

 plasm and gradual approach to spherical form without destruction of the 

 pellicle. In a certain range of concentration of HCl a wave of complete 

 cytolysis of ectoplasm runs from anterior to posterior end (Fig. 28, E, F). 

 In methylene blue and other basic dyes in toxic concentrations the anterior 

 region of the ectoplasm gradually becomes more deeply stained than other 



3 Child, 1914a; Bills, 1924; Child and Deviney, 1926. 



