472 



JENNINGS— HEREDITY IN PROTOZOA. 



(April 24, 



from 49.600 microns to 63.160 microns (characteristic form shown 

 ate,. Fig. 6). But the mean length decreased from 202.280 to 175.320 

 microns. This is probably due to rapid multipHcation ; the animals 

 now divide before they reach the length which they had at first. As 

 a result of the increase in breadth and decrease in length, of course. 



Fig. 6. a and b, characteristic slender specimens from row 13, Table 

 XVIII. c, characteristic short plump specimen from row 14, Table XVIII. ; 

 produced by allowing those of row 13 to remain 24 hours in fresh hay in- 

 fusion. Descendants of D (caudatum form). All X 235. 



the mean ratio of breadth to length increased greatly, from 24.593 

 per cent, to 36.123 per cent. With the increase of this ratio, the 

 correlation likewise increased, as is usually the case. The variation 

 increased, both in breadth and in length. 



These are the results if we consider separately the two samples, 

 taken forty-eight hours apart. But if we throw them together, look- 

 ing at them merely as a sample of the descendants of D, taken at 

 intervals, we get a surprising effect on the correlation between length 

 and breath. The marked positive correlation in the two samples 

 taken separately disappears and is replaced by a negative correlation. 

 In the first sample the correlation is -\- .4085 ; in the second it is 

 4" -5376; in the two together it is — -2613. (The constants for the 

 two together are given in row 15, Table XVIIL) The negative 

 correlation is, of course, due to the fact that the nutritive fluid causes 

 the breadth to increase and the length to decrease, so that, on the 



