ACTIVATION' OF UNFERTILIZED STARFISH EGGS. 



109 



The combined action of the NaCl solution and the current thus 

 shows no significant difference from that of the pure solution 

 alone. The increase noted in the first four experiments was 

 probably the result of a slight rise of temperature; this increases 

 the activating effect of the XaC'l solution, as control experiments 

 showed. 



Decreasing the conductivity of the medium by adding isotonic 

 sugar solution to the sea water was also found not to alter the 

 effect of the current on the eggs. 



In conclusion brief mention should be made of similar experi- 

 ments with Arbacia eggs. The results of these experiments were 

 mainly negative. Little or no effect was produced by exposing 

 the eggs in standing sea water to current-densities varying from 

 7.5 to 210 ma. /cm. No membranes were formed and no cleavage 

 resulted. Eggs exposed to the current and immediately after- 

 wards treated with hypertonic sea water showed no constant 

 increase in the percentage of activation, above eggs treated with 

 hypertonic sea water alone. The effect of exposing to currents of 

 high density in running sea water was also essentially negative, 

 although some cytolysis was caused by the longer exposures. In 

 general the Arbacia egg is more resistant tg the current than the 

 Asterias egg; this difference is probably to be correlated with the 

 greater impermeability of the surface layer to water l (and pre- 

 sumably to water soluble substances) and its greater resistance to 

 alteration and the action of parthenogenetic agents in general. 



SUMMARY. 



1. A new type of non-polarizable (Zn-ZnSO 4 ) electrode of low 

 resistance is described by which strong electric currents (up to 2 

 amperes or more) can be passed for prolonged periods through a 

 small quantity of sea-water without appreciably affecting its 

 composition. 



2. It was found that unfertilized starfish eggs can be readily 

 and completely activated by moderate currents, of the density 

 200-300 milliamperes per square centimeter; but that the effect 

 in.^uch cases is due almost entirely to the heating action of the 

 current on the sea- water. When the temperature is kept below 

 29 such currents produce little or no effect upon the eggs. 



1 Lillie, R. S., Amer. Jonrn. Pliysiol., 1918, XLV., p. 406; cf. p. 420. 



