I90S.] 



JENNINGS— HEREDITY IN PROTOZOA. 



441 



Since then the specimens beginning fission are not the longest of 

 the culture, it is clear that the length decreases before fission begins. 

 This is borne out by the form of the specimens beginning fission; 

 though their mean length is less than that of the random sample, 

 their mean breadth is greater (mean breadth 50.220 microns in the 

 random sample, 55480 in those beginning fission). While then the 



Table XI. 



Correlation Table for Depth of Constriction and Total Length in 313 Dividing 

 Specimens from a Single Culture of Descendants of D. 



All taken the same day. 



Total Length of Body, in IMicrons. 



g 156 160 164 168 172 176 180 184 188 192 196 200 204 208 212 216 220 224 



.<^ 4 



S 8 



c 12 



'I 16 



o 20 



tj 24 



■5 28 

 S 32 



c3 36 

 ^ 40 



o 44 



g- I 10 17 29 44 38 47 30 20 22 16 10 10 6 3 6 2 2 313 



Q 



Length — Mean, 181.725 ± .512M Depth of Constriction — Mean, 13.265^ 



St. Dev., 13-446 dt .362M St. Dev., 2.721M 



Coef. Var., 7.399 ± .201 



Coef. of Cor. between Depth of Constriction and Length, .6882 ± .0201 ; 



Increase in Length for i unit of depth, .860^1 ; Coef. of Cor. if first row is 



omitted, .7818 ± .0194. 



length decreases preparatory to fission, the breadth increases at the 

 same time. How long before fission this change of dimensions 

 begins I can see no way of determining. The period may perhaps 

 be one or two hours. 



Thus, the longest individuals of the culture are the adults that 

 have not begun the changes preparatory to fission. These decrease 

 in length and increase in breadth before fission. 



PROC. .-VMER. PHIL. SOC. XLVIL I90 CC, PRLNTED JANUARY 9, I909. 



