igos.l JENNINGS— HEREDITY IN PROTOZOA. 469 



the minimum size remained as before; and between these extremes 

 all intermediate gradations were found. Fig. 5 shows characteristic 

 forms and sizes from this culture, a and h showing the starving con- 

 dition, while c to / show various stages in the transition to the largest 

 size, one of which is shown at g. 



As a result of these changes, the variability has increased enor- 

 mously. The coefficient of variation in length has increased in 

 twenty-four hours from 7.003 to 12.767; that for breadth has more 

 than doubled, increasing from 12.473 to 28.879. The mean size has 

 likewise increased greatly, while the ratio of breadth to length has 

 changed from 21.2,2,7 per cent, to 28.236 per cent. Perhaps the most 

 striking change is in the correlation between length and breadth. In 

 the starving culture this is but .3906 ; twenty- four hours later it has 

 become, in the growing culture, .8463 — one of the highest coefficients 

 of correlation that I have ever found in Parameckim. It is evident 

 that breadth and length are increasing proportionately, on the whole, 

 so that the inclusion of different degrees of increase in size in Table 

 XX. gives a high coefficient of correlation. Furthermore, the fact 

 that fission had not begun in this lot permits the correlation to remain 

 high; if there were many young included, the correlation would, of 

 course, be lowered. With every increase of 10 microns in length the 

 breadth increases 5.452 microns. 



Fluid Unchanged for a Week. — Now the same culture was kept 

 for a week in the same fluid. The animals had reached more nearly 

 a condition of equilibrium; the variability, and with it the correla- 

 tion, had greatly decreased, while the mean length had increased 

 (Table XXL, and row 10, Table XVIII.). It is noticeable here, as 

 in many other cases, that the coefficient of correlation decreases when 

 the ratio of breadth to length decreases. 



Forty-eight Hours in Nezv Culture Fluid. — The addition of new 

 hay infusion to the culture just described caused in forty-eight hours 

 a considerable increase in mean length and breadth, while the varia- 

 tion did not change greatly (Table XXII., and row 11, Table 

 XVIII.). Again, as the ratio of breadth to length increases, the 

 correlation between the two likewise increases. 



Resume. — Polygons showing the changes in the animals of this 

 series, from the starving condition of Table XIX. to the well-fed 



