280 University of California Publications in Zoologij [Vol. IS 



roboration of theory that more per hour were obtained in the coldest 

 than in the next coldest water? 



Although the hauls are too few and the temperature range in each 

 group is too small to justify retabulation relative to a still smaller 

 range, it is found that the abundance of solitary forms relative to 

 temperatures between 15?9C and 16?5C is 75 per hour, while that 

 relative to temperatures having the same range (0?7C) between 16?6C 

 and 17?2C is 36 per hour. That the significance of this fact may be 

 better appreciated, the abundance of solitary forms and mean tem- 

 peratures relative to the two lowest temperature groups as shown by 

 tables 11, 12, 13, and 14 are brought into relation to the fact just 

 mentioned in the following lists: 



Presented in this way, list A shows that solitary forms decreased 

 in abundance as the mean temperature increased from 16?43C to 

 16?65C, while list B shows that they increased in abundance as the 

 mean temperature increased from 17?00C to 18?39C. How is this 

 apparent paradox to be explained except on the assumption that the 

 number of solitary forms with long protruding chains exceeded the 

 number of detached solitary forms plus the number with short pro- 

 truding chains when the temperature of the water was on the average 

 below 16?7C, while when it was above 16?9C, the number of detached 

 solitary forms plus the number with short protruding chains exceeded 

 the number with long protruding chains? 



Is it not striking that the relations revealed by tables 11 to 14 

 verify the deductions from the theory of chain locomotion almost to 

 the smallest detail? In order that this may be better visualized, the 

 relation between the two generations in abundance and frequency is 

 presented in the form of histograms by plates 10 and 11, figures 4 

 to 11. 



