ELECTRICAL CONDUCTIVITY OF FERTILIZED AND UNFERTILIZED EGGS. 51 



cases the development ceases at an early stage. In all my experiments, 

 except where specially mentioned to the contrary, the eggs developed 

 normally, although in some cases more slowly than the controls. 



The temperature at which the experiments were made never differed 

 much from room temperature, so that it was found possible to keep the 

 temperature of the eggs constant to within yo° centigrade by means of a 

 simple thermostat. The whole apparatus stood in a large earthenware 

 bowl containing water at room temperature. 



The alternating current was obtained from a 2- volt accumulator 

 connected to a small induction coil of high frequency. The resistance was 

 measured by means of a Kohlrausch bridge (half a metre in length), and a 

 telephone. The electrodes were platinized in the usual way by means 

 of platinic chloride with a trace of lead acetate. The induction coil was 

 placed outside the room in which the experiments were made, and by keep- 

 ing the electrodes well platinized it was possible to obtain quite distinct 

 minimal points with an ordinary telephone. 



Methods. 

 The procedure adopted during the whole of the experiments was as 

 follows : The ovaries of a perfectly ripe female were shaken in one or 

 more finger-bowls containing " outside " water. The ovaries were 

 removed after five or ten minutes, and the sea-water containing the eggs 

 filtered through a suitable piece of bolting silk. In this way any loose 

 pieces of ovarian tissue were removed from the eggs. The latter were 

 now allowed to settle to the bottom of the bowl. The ripe eggs settled 

 somewhat slowly, but after a short time sufficient eggs for one experiment 

 could be drawn off in a clean pipette ; thence they were transferred to the 

 conductivity tube. The requisite amount of eggs having been so ob- 

 tained, the tube was filled up with clean sea-water, corked and allowed 

 to stand in a bowl of sea-water until the eggs had again settled sufficiently 

 for the bulk of the sea-water to be removed. This having been done, the 

 eggs were again washed in clean sea-water. After two or three such 

 washings all the small fragments of tissue smaller than the eggs were 

 removed, and the tube contained nothing but ripe eggs in clean sea- 

 water. After washing in this way the eggs settled somewhat more 

 readily than when removed from the ovary, owing to the removal of the 

 gelatinous ovarian membranes. The conductivity tube containing the 

 eggs was then transferred to the thermostat and left until the eggs had 

 settled to a definite volume which could be estimated without any 

 difficulty. Great care was used to ensure that the eggs settled uniformly 



