HURWITZ. 



THE REACTIONS OF EARTHWORMS TO ACIDS- 



69 



when the worms were kept in tap-water, but seldom occurred when 

 they were allowed to crawl on the filter paper. 



After the worm under ordinary circumstances had withdrawn fi-om the 

 solution, it was rinsed in tap-water, returned to its glass, and allowed 

 to rest about five minutes before another trial with it was made. 

 To rule out the possible disturbing factor of fatigue, it was decided to 

 use no worm for more than a given, arbitrarily determined, number of 

 reactions (twelve). 



The acids were first experimented with in pairs ; each acid being 

 compared with every other one ; hydrochloric acid, for instance, being 

 compared with nitric, sulphuric, and acetic acids successively. Al- 

 though it is not known that the particular sequence in which the acids 

 are used makes any material difference, nevertheless to avoid any error 

 which might possibly creep in by passing from a more to a less stimu- 

 lating acid, the solutions were used alternately ; for it is highly proba- 

 ble that when a strong solution is first applied, the effect of it is apt to 

 be so vigorous as to obscure a subsequent response to weaker solutions. 

 Where all the acids were compared at once the procedure adopted was 

 to give each acid first place with at least one worm of those tested. 



In tables I to XVI will be found the reaction-times of the earth- 

 worm, Allolobophora foetida, for the four different acids used. 



Tables I to XVI. — Reaction Times, in Seconds, of Allolobophora foetida 

 to Solutions of Nitric and Hydrochloric, Sulphuric and Hydrochloric, Sulphuric 

 and Nitric, and Hydrochloric and Acetic Acids. 



TABLE I. 

 ^0 HNOa. 



