ACTIVATION" OF UNFERTILIZED STARFISH EGGS. IO5 



by sea-water which had been warmed to 30 or higher by the 

 current, the latter being shut off before the eggs were introduced. 



It seems probable, nevertheless, that a part of the activating 

 effect observed in this and similar experiments is to be attributed 

 to the current; i.e., that there is a summation of the effects of heat 

 and current, since the degree of activation was greater than would 

 usually be produced by exposure to a temperature of 30 for the 

 periods used. According to earlier observations, activation by 

 warm sea-water (acting alone) requires a temperature of at least 

 29, and at 30 few eggs develop to a blastula stage after less than 

 15 minutes' exposure. 1 In other words, the effect of high temper- 

 ature appears to be greater when a current is flowing through the 

 sea-water containing the eggs than when no current is flowing. 

 We have not, however, performed definite controlled experiments 

 to determine with exactitude the degree of this additive effect. 

 An analogous phenomenon is seen in the activation of starfish eggs 

 by fatty acid; at temperatures of 26 and higher the effective 

 times of exposure to the acid are much shorter than can be 

 accounted for by the temperature coefficient of acid activation 

 (Qio == ca. 3.0) shown at lower temperatures. 2 Apparently in 

 warm sea-water the action of the fatty acid is accelerated by 

 some condition dependent on temperature; i.e., there is a super- 

 position of acid activation upon an incipient heat activation. 

 Similarly, in the experiments with strong currents an effect 

 resulting from the action of the current as such appears to be 

 superposed upon that of the high temperature. 



With current-densities higher than 240 ma. /cm. the difficulty of 

 evading the temperature effect was such that it was necessary to 

 devise another means of compensating the heating action of the 

 current. We therefore tried exposing the eggs to strong currents 

 in running instead of stationary sea-water, and after some pre- 

 liminary experimentation adopted the following procedure: In 

 place of the rectangular glass dish a paper box of the same 

 dimensions was used. This was reinforced and made an electric 

 non-conductor by several coatings of paraffin. A rectangular slit 

 (ca. 6 x 1.5 cm.) was cut at the base of this box along one of the 

 longer sides. A small rectangular cloth basket (ca. 3x3x4 cm.), 



1 Lillie, R. S., BIOL. BULL., 1915, XXVIII. , p. 260; cf. Table II., p. 269. 

 2 Lillie, R. S., BIOL. BULL., 1917, XXXII., p. 131; cf. Table II., p. 142. 



