igos.] JENNINGS— HEREDITY IN PROTOZOA. 447 



each of the two component lots taken separately, since the two lots 

 dififered as a result of different environmental conditions. 



(n) Later Stages of Fission. — As the constriction deepens the 

 animal as a whole becomes more elongated, while the breadth de- 

 creases slightly. These relations are shown both for the descendants 

 of D (candatiiiii form) and the descendants of c (aurclia form) in 

 Table X. (rows 25 and 26; 30 and 31 ; 33 and 34). In the large lot 

 I of dividing descendants of D, comprising 313 specimens (Table 

 XI.) the correlation between length of body and depth of constric- 

 tion below- the surface is .6882. The length increases 8.6 microns 

 with every increase of 10 microns in the depth of constriction. The 

 correlation between breadth and depth of constriction (Table XII.) 

 is — -5232, the breadth decreasing 2.63 microns for each 10 microns 

 increase in depth of constriction. If we include only the specimens 

 in which lengthening has decidedly begun (thus omitting the earliest 

 stages, in the uppermost rows of Tables XL and XII.), then the 

 correlation between length and depth of constriction is .7818; between 

 breadth and depth of constriction, — -3316. With an increase of 10 

 microns in depth of constriction the length now increases 11.195 

 microns, while the breadth decreases 1.252 microns. In this same 

 culture while the mean length of the 131 specimens beginning fission 

 is 175.696 microns, that of the seven specimens having a connecting 

 portion but 4 microns wide is 212.572 microns. Thus, the increase 

 in length before separation takes place is 36.876 microns, or about 

 21 per cent, of the length at the time fission begins. The breadth 

 has decreased from 55.480 microns at the beginning of fission to 

 43.428 microns in the seven specimens with the narrowest connec- 

 tions — a decrease of about 21 per cent. The ratio of breadth to 

 length decreases from 31.568 per cent, at the beginning of fission to 

 20.430 per cent, just before separation. 



Corresponding relations are shown in other lots of dividing speci- 

 mens ; some of the data are given in Table X. 



2. Summary ox Growth ix Paramecium with a Growth Curve. 

 We have thus followed the growth from the time when the indi- 

 vidual is but half a constricting specimen to the period when it is 

 again ready to separate into two new individuals. \\q are ready. 



