THE ACTIVATION OF STARFISH EGGS BY ACIDS : II. THE ACTION OF SUBSTITUTED BENZOIC ACIDS AND OF BENZOIC AND SALICYLIC ACIDS AS INFLUENCED BY THEIR SALTS.
1. Comparison of the rates of activation of unfertilized starfish eggs in pure solutions of a variety of parthenogenetically effective organic acids (fatty acids, carbonic acid, benzoic and salicylic acids, chloro- and nitrobenzoic acids) shows that solutions which activate the eggs at the same rate, although widely different in molecular concentration, tend to be closely similar in C(H). The dissociation constants of these acids range from 3.2 x 10(-7) to 1.32 x 10(-3). 2. In the case of each of the fourteen acids showing parthenogenetic action the rate of activation (within the favorable range of concentration) proved nearly proportional to the concentration of acid. The estimated C(H) of solutions exhibiting an optimum action with exposures of 10 minutes (at 20 degrees ) lay typically between 1.1 x 10(-4)M and 2.1 x 10(-4)M (pH = 3.7-3.96), and in most cases between 1.6 x 10(-4)M and 2.1 x 10(-4)M (pH = 3.7-3.8). Formic acid (C(H) = 4.2 x 10(-4)M) and o-chlorobenzoic acid (C(H) = 3.5 x 10(-4)M) are exceptions; o-nitrobenzoic acid is ineffective, apparently because of slow penetration. 3. Activation is not dependent on the penetration of H ions into the egg from without, as is shown by the effects following the addition of its Na salt to the solution of the activating acid (acetic, benzoic, salicylic). The rate of activation is increased by such addition, to a degree indicating that the parthenogenetically effective component of the external solution is the undissociated free acid. Apparently the undissociated molecules alone penetrate the egg freely. It is assumed that, having penetrated, they dissociate in the interior of the egg, furnishing there the H ions which effect activation. 4. Attention is drawn to certain parallels between the physiological conditions controlling activation in the starfish egg and in the vertebrate respiratory center.
Lillie
R S
RS
Marine Biological Laboratory, Woods Hole, and the Laboratory of General Physiology, University of Chicago, Chicago.