H. H. NEWMAN. 



and allowed to develop. In every case nearly all eggs developed 

 normally and formed embryos. 1 



It is worthy of note, then, that the egg becomes immensely 

 more resistant to the toxic action of these salts after fertilization. 



Several repetitions of Experiment I. showed an invariable order 

 of activity from the most active to the least active CaCl 2 , 

 MgCl 2 , NaCl, KC1. It seemed advisable to include several 

 other chlorides of these groups to see if their activity in inhib- 

 iting fertilization would fall in line with the theory of solution 

 tension. 



Experiment III. A large number of eggs were stripped 

 into distilled water, stirred and distributed into seven dishes con- 

 taining : 



A. T % n. LiCl, E. t \ . CaCl 2 , 



B. T % . NaCl, F. f% . SrCl 2 , 



C. T <V . KC1, G. T % n. BaCl 2 . 



D. fr . MgCl 2 , 



All eggs were allowed to remain in these solutions for five 

 minutes, then washed and an attempt made to fertilize them in 

 sea water, abundance of sperm being added in each case. It 

 was found that so few of the eggs cleaved that a percentage basis 

 could not be employed for all of the salts, yet it was quite evi- 

 dent that LiCl had an action between NaCl and MgCl. 2 , while 

 SrCl 3 and BaCl 2 fell between MgCl 2 and CaCl 2 . 



Evidently the concentration of the seven salts used in this ex- 

 periment was too great so it seemed advisable to determine the 

 minimum concentration and the minimum time of exposure re- 

 quired by the most active of these salts - - CaCl 2 for complete 

 inhibition of fertilization. The following experiment enabled me 

 to determine this. 



Experiment fV. Solutions of -J^ ;/ -> -TO n -> To l! - anc ^ iV ;/ - so \ u ~ 

 tions were made up and lots of eggs were exposed in each con- 

 centration for five, ten, twenty and thirty minutes before fertiliza- 

 tion was tried. It was found that a ^ n. CaCl., solution, after 

 acting for five minutes allowed only o to 4 per cent, of eggs to 

 become fertilized. This concentration and time of exposure 

 should give a good percentage basis for estimating the activity 

 of the seven salts used with reference to CaCl.,. 



1 See Mathews, American Journal of Physiology, X., 1904, p. 241. 



