LOEB. 3 I I 



possibility that such catalytic effects might also be brought about 

 through enzymes or other substances is of course not shut out. 

 Yet this fact must be considered : that we have been able to pro- 

 duce artificially normal embryos capable of development through 

 ions, while the careful experiments of Gies conducted in my 

 laboratory in which he attempted to find the same to hold for 

 enzymes have thus far failed. 



In conclusion I wish to thank my assistant, Mr. Xeilson, for the 

 assistance which he rendered me in these experiments. 



