436 JENNINGS— HEREDITY IN PROTOZOA. [April 24, 



in Table X., row 11. The variability, as measured by its coefficient, 

 is less in both length and breadth than in the random sample, or in 

 the collection of young specimens includingonly those under nineteen 

 minutes in age. There is practically no correlation in the collection 

 taken as a whole between length and breadth. This is because 

 breadth at first decreases while length increases (giving negative 

 correlation) ; later they increase together (giving positive correla- 

 tion) ; the two tendencies about cancel each other in the collection 

 as a whole. 



Third Stage: Three to Five Hours Old {Tables XXXVII. and 



XXXVIII.) . 



Three days later than the sets shown in lot 6, Table X., and 

 under as nearly the same conditions as possible, I took from the same 

 culture of progeny of D two sets of young, keeping the first set till 

 the age was between 3 and 4 hours, the second set till the age was 

 between 4.20 and 5 hours (see lot 9, Table X.). The culture was, 

 however, in a dififerent condition from that of lot 6; it contained a 

 very large number of young and dividing specimens. A random 

 sample of this culture, containing 195 specimens, is shown in Table 

 VII. (page 412), while the constants for this sample are shown in 

 row 19, Table X. The entire left portion of Table VII., up to the 

 length of about 160 microns, or more, evidently consists of young 

 individuals in various stages of growth. This decreases the main 

 length (176.124 microns) and the correlation (.3945), while it greatly 

 increases the variability in length (13.262, as against 6.821 for the 

 random sample of the previous lot). 



(i) Age 3 to 4 Hours {Table ZZXF//.).— The , effects of dif- 

 ferent environmental conditions are at once seen on comparing this 

 set of 93 specimens (Table X., row 16) with the set 75 to 90 minutes 

 old, from the previous culture (Table X., row 10). The specimens 

 of the present lot, though li to 23 hours older than the others, are 

 shorter, the length (149.636 microns) being less by about 16 microns. 

 The breadth is about the same as in the previous set ; the correlation 

 between the two is rather low (.3201). 



(/) Age 4.20 to 5 Hours (Table XXX F///.).— Ninety-five 

 specimens kept for about an hour longer than those in the foregoing 



