Races of Paramecium. 



519 



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Fig. 17. A collection of individuals from a culture in which the two aurelia 

 races i and k have been living rogether for three weeks, to show the differences 

 between the two races when living in the same medium. The upper row (a to d) 

 shows characteristic individuals of k, the lower row (e to h) individuals of i. a 

 and e show a dextro-ventral view; b and / the dorsal surface; c and g the ventral 

 surface, d shows the left side; h the sinistro-ventral surface, a and c are dif- 

 ferent views of the same individual; note the difference in form. Edinger drawing 

 apparatus. X 375. 



