122 MORPHOLOGIC VARIATION 



in classes according to their area-length indices. The values given 

 are the maxima for the class, thirty for instance indicating all of 

 the cells with area-length indices from 25.1 to 30.0. This shows 

 well the variation from long, slender, curved cells, on the one hand, 

 to small, spherical cells on the other. 



It will be noted from the frequency distribution curves that the 

 cells introduced into the medium apparently consisted of a large 

 group of relatively slender cells distributed about one mode, and 

 a small group of more oval cells distributed about another. As 

 growth proceeded the frequency distribution curves exhibit a regular 

 change in form. The minor mode is gradually absorbed and disap- 

 pears; the range becomes restricted, the mode higher; and at eighteen 

 hours we have a tall, symmetrical curve. With the beginning of 

 the death phase the frequency curves again return to the form ex- 

 hibited by the cells used for seeding; the base becomes extended, 

 the mode lower; and there appears a new minor mode of oval cells, 

 which reaches its maximum at four days, and then again disappears, 

 the final curve at ten days being simply a much skewed curve with 

 a broad base. 



These variations in the frequency distribution are reflected in 

 the coefficients of variability of the area-length index, presented in 

 Table XXIV. This value showed considerable fluctuation, but was 

 distinctly lower during the period of active growth from nine to 

 eighteen hours, and increased again with the cessation of growth 

 to reach its maximum at four days. Since the area-length index 

 does not classify the asymmetrical cells, an attempt has been made 

 to follow these roughly by simple inspection of the drawings, and 

 the results are given in Table XXV. It will be seen that the per- 

 centage of asymmetrical cells steadfly decreased during growth, the 

 number remaining low until the beginning of the death phase at 

 forty-eight hours, when they again increased, reaching a maximum 

 at four days, after which there was again a slight decrease in num- 

 ber. 



With all of these measurements at hand we are now in a posi- 

 tion to say something more precise concerning the three types of 

 cefls previously mentioned. During the initial period of dormancy 

 the cells showed no pronounced variation. With positive accelera- 



