786 SALT ANTAGONISM IN STARFISH EGGS 



water at the following intervals: \,^, 1, 2, 3, 4, 6, 8, and 12 minutes; 

 after 20 to 30 minutes in sea water, eggs from each bowl of the series 

 were examined on a slide in India ink suspension. It was found 

 that the jelly still remained about eggs that had been exposed to the 

 NaCl solution for so long as 3 or 4 minutes, but that by that time 

 it was swollen to several times its original volume, so that the boun- 

 dary of the ink suspension was often separated from the egg by a 

 full egg diameter. In eggs exposed to NaCl solution for 6 minutes 

 and examined under the same conditions the jelly had completely 

 disappeared from a large proportion of eggs, though still remaining 

 in a greatly swollen form in most. After 12 minutes exposure the 

 ink was in nearly all cases in contact with the egg surface, indicating 

 complete removal of the jelly. 



The removal of the jelly in NaCl solution is completely prevented 

 by the addition of a small proportion of CaCl2. The agglutinating 

 and membrane-forming effects above described are at the same time 

 prevented or greatly decreased. Since these two latter effects are 

 dependent upon alteration of the surface layer of the living pro- 

 toplasm, this parallelism suggests that the calcium prevents the 

 physiological action of the pure NaCl solution through some character- 

 istic influence on the solubility or hydration of certain compounds 

 which are present in the protoplasmic surface layer and upon which 

 the normal properties of this layer depend. 



The following typical experiment (June 18, 1920) will illustrate. 

 Starfish eggs were removed from the animal at 3.06 p.m.; the eggs 

 were normal; all showed the typical jelly envelope in India ink sus- 

 pension; more than 90 per cent underwent maturation and upon 

 fertilization developed to larval stages. At 3.48 p.m. the two 

 tubes of a hand centrifuge were filled with a suspension of unfer- 

 tilized eggs in sea water and gently centrifuged until the eggs were 

 settled in a mass about one-third of an inch deep in the narrow part 

 of each tube. The sea water was then poured off and replaced 

 in one tube by pure 0.54 m NaCl (lot A), in the other by a mixture 

 of 250 cc. 0.54 M NaCl plus 15 cc. m/2 CaClj (lot B). The solutions 

 were added at 3.49 p.m.; the tubes were then gently centrifuged to 

 settle the eggs and the solution was changed; this procedure was 

 repeated. The eggs were then returned to sea water. The total time 



