JENNINGS— HEREDITY IN PROTOZOA. 



491 



Table XXIV. 

 Mean Dimensions in Microns of the Five Lines E, D, c. g and i, when Culti- 

 vated under the same Conditions, January 19 to February 5 and 

 February 5 to February 15. 



2. At least four distinct lines are present, D, c, g and i; these 

 maintain their relative different sizes throughout the experiments, 

 which lasted about twenty-five generations. 



3. The lines E and D are nearly or quite the same. On February 

 5 they show nearly the same measurements, but on February 15 

 there was a marked difference. To test the meaning of this these 

 two were cultivated twelve days more; then on February 27 they 

 gave again nearly the same measurements. It will doubtless be 

 safest to consider them the same. 



We have now, therefore, four dift"erent lines or races of Para- 

 mecium, characterized by persisting relative dift'erences m size. 

 One of these (D and E) belongs, from its size, to the " candatuin 

 group " ; the other three are much smaller and fall in the " aurelia 

 group." Of these, g is the largest, i the smallest, while c is inter- 

 mediate. Under a similar change in the environment these all change 

 in a corresponding way, as is shown by the fact that on February 15 

 all were somewhat larger than on February 5. It may be noted that 



