314 REUBEN BLUMENTHAL. 



measuring the changes in the diameters of the eggs with an ocular 

 micrometer. Eggs from a single individual were placed in con- 

 centrations of HCN varying from N/^oo to N/2,ooo. At the 

 end of ten minutes and again after 25 and 66 minutes, eggs were 

 pipetted into a 50 per cent, solution of sea-water (hypotonic) and 

 their diameters measured at regular time intervals. A control 

 was kept in which sea-water replaced the HCN solutions. 



The HCN solutions were prepared by drawing over, by means 

 of an aspirator, into a wash bottle containing distilled water, the 

 volatile HCN gas from another bottle containing KCN to which 

 a few drops of acid had been added. The amount of HCN going 

 into solution was determined by titrating with o.i N AgNO 3 ; 

 i.o cc. of the nitrate being equal to 0.013 gram HCN. It was 

 necessary to use distilled water because the chlorides in the sea- 

 water interfered with the titration. The desired concentrations 

 of HCN were then made up with sea-water. All the sea-water 

 mentioned in these experiments was sea-water from which COa, 

 in excess of that in equilibrium with the CO% in the air, had been 

 removed. This was done by adding 2.4 cc. of o.i N HC1 per 

 liter of sea-water and aerating for 18 to 24 hours. NaOH or 

 HC1 was then added to bring it to the pH of normal sea-water. 



The eggs, after exposure to the cyanide solutions, were placed 

 in Syracuse watch-glasses containing the hypotonic solution and 

 a 4 mm. objective used as a water immersion with a loX ocular. 

 This gave a magnification of 450 X. Readings were taken one 

 minute after placing in the hypotonic solution and thereafter 

 every minute for ten or fifteen minutes. A stop watch was used 

 to read time intervals. The following abstract taken from daily 

 notes will show the routine followed throughout the experiments. 



7/20/26. Temperature of room 21 C. pH of HCN solution 

 measured colorimetrically =7.2. gA.M. unfertilized Arbacia 

 eggs placed in 30 cc. of N/^oo HCN in a finger bowl and covered. 

 g.io A.M. eggs pipetted into 5 cc. hypotonic sea-water in watch 

 glass and diameter of eggs measured every minute for ten minutes. 

 Three perfectly spherical eggs were measured each time and the 

 average taken. 9.25 A.M. some eggs from original N/$oo HCN 

 solution placed in hypotonic solution and ten one-minute readings 

 again taken. Temperature of room 21.2 C. 10.06 A.M., after 



