No. 3-] BIOLOGY OF THE STENTORS. 541 



factor, that of food, was not uniform, and it seemed impossible 

 to make it so. While at the outset all the cultures probably 

 contained nearly the same amount of available nutriment, the 

 more extensive growth of plant-life and the greater multipli- 

 cation of minute organisms {e.g. Arcella) in some of the 

 cultures, placed the inhabitants of those cultures at great 

 advantage. Hence the wide difference in the number of 

 Stentors in the different cultures. 



A month later a census was taken of the colonies, with the 



Remarks. 

 Large to small ; well-fed. 

 Mostly small ; not well-fed. 

 Small ; moribund. 

 Large to small ; well-fed. 

 Average size ; well-fed. 

 Average. 



Large to small ; mostly well-fed. 

 Large to very small ; well-fed. 



The record shows an increase for all colonies except Nos. 3 

 and 6, which obviously were suffering from lack of food. The 

 great variation seen in the increase of the other colonies is 

 doubtless almost entirely due to the great difference in the 

 amount of available food. But the experiment at least shows 

 that the dwarf Stentors are not incapable of growth, and under 

 favorable circumstances will multiply as rapidly as large ones ; 

 for, comparing the cultures by twos (No. i with No. 2, No. 5 

 with No. 4, No. 7 with No. 8), we find in every instance a 

 balance in favor of the small Stentors. 



It is worthy of note that although the ten brood Stentors 

 used in starting each culture were very nearly alike in size, 

 their descendants soon came to show the usual marked differ- 

 ence in that respect. 



Very interesting in this connection are the recently-published 

 observations of Gruber ('92) upon dwarf Stentors. The occur- 

 rence of a natural colony of Blue Stentor dwarfs, all of which, 

 as far as examined, possessed a simple nucleus the size and 

 shape of a single node of the usual moniliform nucleus, was 



