446 JENNINGS— HEREDITY IN PROTOZOA. [April 24, 



specimens (Table XLVI.).^ Selecting from these, as representing 

 the early stages of fission, all those in which the depth of constriction 

 is less than one fourth the diameter of the body, we obtain from the 

 larger lot 66 specimens (Table XLVII.) ; from the smaller lot 38 

 specimens (Table XLVIIL). The constants for these, in compari- 

 son with those for random samples, are given in Table X. (lots 4 

 and 5, rows 33 to 38). The measurements of the random samples 

 are shown in Tables XLIX. and L. 



These specimens of the aiirelia form show the same relations 

 that are found in the caudatnin form, with one exception. In lot 5 

 (Table X., row 36) the mean breadth of the specimens beginning 

 fission is less than that of the random sample, instead of greater as 

 in all other cases. But this peculiarity is due to environmental con- 

 ditions. In lot 5 the breadth was very great in proportion to the 

 length, as is shown by the dimensions of the random sample (Table 

 L., and row 37, Table X.). In this lot the breadth was 41.555 per 

 cent, of the length, while in most cases it is near to 30 per cent. 

 This was due to the recent transference of the animals to a nutritive 

 solution; they became very plump. Evidently, when preparing to 

 divide the body tends to return to a constant form ; in this case, 

 therefore, it becomes narrower instead of broader. 



In the specimens of the aurclia form, as in the caudatnin form, 

 all dimensions are less variable in the specimens beginning fission. 

 This difference in variability, as compared with the random samples, 

 is very great in some cases. Thus, while the coefficients of variation 

 in length for the random samples of lots 4 and 5 are 15.279 and 

 10.643, ^'^^ those of the same lots beginning fission they are but 7.541 

 and 6.862, respectively. Had we included in the lots beginning fission 

 only specimens in which the depth of constriction was still less, the 

 coefificients of variation would have been still smaller. 



The constants for all specimens of c that are beginning fission, 

 taken together, are shown in row 38, Table X. The standard devia- 

 tions and coefificients of variation are, of course, greater than for 



° In making these measurements of descendants of c, a higher power of 

 the microscope was used, so that the single tinit of measurement was 3J 

 microns. This caused the tables (in the appendix) to take a somewhat differ- 

 ent appearance from those of the descendants of D. 



