THE PHYSIOLOGY OF CELL-DIVISION 
IV. THE ACTION OF SALT SOLUTIONS. FOLLOWED BY HYPERTONIC 
SEA-WATER ON UNFERTILIZED SEA-URCHIN EGGS AND THE 
ROLE OF MEMBRANES IN MITOSIS 
RALPH S. LILLIE 
From the Marine Biological Laboratory, Woods Hole, and the Physiological Labor- 
atory, Department of Zoology, University of Pennsylvania 
THREE FIGURES 
INTRODUCTION 
During the summer of 1909 at Woods Hole I found that mem- 
brane-formation and cleavage, leading in a small proportion of 
cases to the production of blastulae, could be induced in unfer- 
tilized eggs of Asterias and Arbacia by temporary exposure to 
isotonic solutions of various neutral salts.!. Salts of sodium and 
potassium were chiefly employed, including chloride, bromide, 
nitrate, iodide and sulphocyanate; last summer chlorate was 
also used. In the case of Asterias all of these were found to 
induce membrane-formation and cleavage in a large proportion 
of eggs. With Arbacia, however, only iodide and sulphocyanate 
showed a corresponding degree of effectiveness; nitrate had well- 
marked though less decided action, chlorate produced little and 
bromide still less effect, while chloride was almost entirely in- 
active; sodium acetate was found to act like chloride. The order 
of relative effectiveness of the salts, ranged according to the 
anions, is as follows: COO CH; and Cl<Br<ClO;<NO; <I 
and CNS. This order is also that of relative activity in freeing 
pigment from the eggs; a perceptible loss of pigment occurs within 
two or three minutes in iodide and sulphocyanate solutions and 
more slowly in solutions of the other salts. The exit of pigment 
1R. 8. Lillie: American Journal of Physiology, 1910, vol. 26, p. 106. 
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