432 ALFRED O. GROSS 
When the worms were placed on the fence with sea-water on 
one side and ordinarj^ tap-water or distilled water on the other, 
the worms quickly withdrew into the sea-water, indicating that 
the latter has a marked disturbing effect on Nereis. Because of 
this condition, the special substances used as stimuli weie always 
added to the sea-water. It may not be safe, by this method, to 
make a comparison of the relative stimulating efficiency of one 
acid with another or with an alkali, hydroxide, or salt, because of 
the many substances in solution in sea-water which might affect 
the reagent. One can, however, make comparisons of the rela- 
tive sensitiveness of the worms under different conditions. As 
long as there is a constant stimulating liquid in the mixture of a 
measured quantity of sea-water and a definite amount of the 
chemical, it makes no difference for this purpose what the result- 
ing chemical combinations and mixtures may be. 
For convenience of comparison the various reagents were 
made up in molecular solutions and these solutions were added 
in definite quantities, by means of a burette, to the sea-water 
in the following proportions. 
TABLE 2 
1 cc. mol. HCl to 300 cc. sea-water 
1 cc. mol. KOH to 10 cc. sea-water 
1 cc. mol. NaOH to 10 cc. sea-water 
1 cc. mol. KCl to 10 cc. sea-water 
1 cc. mol. NaH4Cl to 3 cc. sea-water 
1 cc. mol. NaCl to i cc. sea-water 
The worms exhibited a marked reaction when tested with 
mixtures of sea-water and molecular solutions in the proportions 
shown in the above table. 
The reaction times of the worms when tested with these solu- 
tions were short, but not too short to be accurately measured by 
means of a stop-watch. Though these concentrations of salts 
produced only approximately similar reaction times, it is inter- 
esting to note that it required about fifty times as great a concen- 
tration of NaCl as KCl to produce an approximately similar 
reaction time on Nereis; whereas Parker and Metcalf found 
NaCl to be more stimulating than KCl to the dung earthworm, 
Allolobophora foetida. This striking difference is probably 
