514 



H. S. Jennings and George T. Hargitt. 



races full twenty-four or more hours after. Now, after being 

 placed in the fresh infusion, the animals often shorten and thicken 

 greatly, as demonstrated in an earlier paper (Jennings, '08, p. 472). 

 The race 20 passed into fission while still short and thick, the other 

 races not till they had become thinner and more elongated again. 

 The table shows that race 20 was not only shorter than would be 



L2 



20 



D 



C2 



Fig. 13. Characteristic outlines of individuals of certain races at the age of 

 ten minutes, showing relative sizes. Drawn with Edinger drawing apparatus. 

 X 375. 



expected, but also much thicker. Properly, therefore, race 20 

 does not belong in the table, since the conditions for it were differ- 

 ent from those for the other races. 



These facts are an illustration of the physiological differences 

 between races, to be discussed later. In mean adult size, as we 

 have seen, race 20 does not differ appreciably from race L2; but 

 in this matter of the conditions under which fission occurs there 

 is a marked diversity between the two. 



Fig. 13 shows characteristic relative sizes in a number of differ- 

 ent races at the age of ten minutes. 



. To test accurately the relation of these diversities in size to 

 environmental conditions, a number of cultures were set in progress 



