HURWITZ. — THE REACTIONS OF EARTHWORMS TO ACIDS. 77 



TABLE XVI. 



3^5 C2H4O2. 



It will be seen by inspecting the tables that each solution was as a 

 rule used on each one of the five worms six times. The worms were 

 tested in such sequence that when the reaction-times for each acid were 

 averaged the factor of exhaustion was so distributed as to be non-cumu- 

 lative for any class. 



Notwithstanding the care exercised in keeping the experimental con- 

 ditions as nearly uniform as possible, it will be seen that the various 

 worms present striking differences ; some exhibiting characteristically 

 slow, others quick reactions. 



The slow reaction was in the main found associated with two modes 

 of behavior, unlike each other. In not a few of the cases recorded, the 

 portion of the worm anterior to the clitellum would rapidly contract as 

 soon as it cut the surface of the solution, thus exposing a smaller recep- 

 tive area to the action of the acid than would otherwise have been done. 

 In such cases the worm was probably less stimulated and therefore 

 would naturally be slower in withdrawing from the stimulating solution. 

 In many of the slow reactions, the behavior was directly opposite of that 

 just described. After cutting the surface of the solution, the anterior 

 end of the worm would greatly elongate and squirm about, as if testing 

 its environment in all directions. Such random movements executed 

 in an endeavor to escape the stimulus are described by Jennings (:06) 

 for the earthworm. A worm crawling upon a flat surface might escajje 

 an irritating stimulus with which it came in contact anteriorly, either 



