PHYSIOLOGY OF ASCIDIA ATRA LESUEUR 291 
TABLE 8 
Liminal strengths of acids for the stimulation of Ascidia 
ACID CONCENTRATION 
HCl 0.0016 N 
HCOOH 0.0018 N 
CH;COOH 0.010 N 
The order of the stimulating efficiency of the acids is, therefore, 
HCl > formic > acetic 
Bases. As representatives of this group of substances, I used 
NH,OH and NaOH. Exp. VIII.9.1 gave the liminal values shown 
in table 9. This places them in the order, 
NaOH >NH,OH 
TABLE 9 
BASE CONCENTRATION 
NaOH 0.010 N 
NH,OH 0.015 N 
Sugars. Both glycerin and sucrose did not stimulate until 
they reached a concentration of | M. This quantity of solute, 
plus the salts of the seawater in which these substances were 
dissolved, brought the concentration of the stimulating solution 
to just that equivalent of concentrated seawater which irritated 
Ascidia osmotically. We can, therefore, conclude that Ascidia 
is not sensitive to these two substances. 
This has been found to be generally true for aquatic animals 
(Parker, 712). Crozier (15a), however, has shown that glycerin 
and maltose can stimulate Holothuria. 
Alkaloids. The sulphates of quinine, strychnine and morphine 
were tested. The order of their effectiveness, 
strychnine > quinine >morphine 
was found in Exp. VIII.1, the results of which are given in 
table 10. 
These values show a surprising sensitivity of the species to 
alkaloids. A bitter taste in man may be secured from 0.00004 M 
quinine sulphate. This amounts to one-tenth of the uncorrected 
concentration to which Ascidia reacts. 
