8.] 



JENNINGS— HEREDITY IN PROTOZOA. 



451 



dimensions by the ratio between the length of the random samples of the 

 two lots. In lot 9 we use only the average of the two sets, as given in row 

 i8, Table X. 



In lot ID, since we unfortunately have no random sample, we are unable 

 to make a correction. 



Owing to the very great difference in the environmental conditions of 

 lot 3 (row^s 23 and 24, Table X.) we are unable to use the 24-hour-old 

 specimens of that lot, although we need measurements at that age. The 

 older portions of the curve (beyond 18 hours, at the right) cannot be 

 plotted from exact data, and there are certain features of much importance 

 for which it appears that the collection of such data would be almost 

 impossible. As w^e have shown, before fission the animals shorten and 

 thicken. How long before fission this begins it is not possible to say; in 

 making the curve the period is arbitrarily taken as two hours. 



When we make the corrections above described, we have the following 

 mean dimensions at dift'erent ages, as data for the construction of our curve. 

 The ages given are the average ages for the lots considered; thus the age 

 for row 8, Table X. (18 to 28 minutes) is taken as 23 minutes. 



Table XV. 



Dimensions in Microns of Paraniecia {Descendants of D) at Different Ages, 



Corrected {so far as possible) to Correspond with Those of Lot 6, 



Table X. Data used in making the Curves of Growth. 



Age. 



Mean Length 

 in Microns. 



Beginning constriction Row 4, Table VIII. 



Fifteen minutes after beginning 



constriction 



2j4 minutes after separation 



9^ minutes 



23 minutes 



40 minutes 



82^-2 minutes 



4 hours 



1 2 hours 



18 hours 



inning constriction 



Mean Breadth 

 in Microns. 



5. 

 5. 

 7, 

 8, 



9. 

 10, 



iS, 

 20, 

 22, 



VIII. 

 X. 

 X. 

 X. 

 X. 

 X. 

 X. 

 X. 

 X. 

 X. 



82.600 ! 

 85-774 



107.660 

 128.000 



143-348 



149.920 

 161.524 

 176.560 

 188.988 



199.048 

 165.200 



64.893 

 64-493 



59-355 

 60.168 

 54.2S4 

 55-840 

 54.^92 

 58. 922 

 62.796 

 56.496 

 64.893 



When we lay off on the vertical scale the distances corresponding to the 

 lengths and breadths at the different periods, as given in the above table, 

 and connect these points, we obtain the curves given in Diagram 5. 



Characteristics of the Curves. — As the curves show, the length 

 increases with great rapidity for about twenty minutes after fission; 

 continues less rapidly for about an hour, and still less rapidly for 

 four or five hours. Now the increase continues, though very slowly, 

 till a maximum is reached at a length considerably greater than twuce 

 the original length ; later the length decreases in preparation for 



