THE EFFECTS OF SALTS AND SUGAR SOLUTIONS 

 ON THE DEVELOPMENT OF THE FROG'S EGG. 



T. H. MORGAN AND C. R. STOCKARD. 



The purpose of these experiments was to determine more defi- 

 nitely what action takes place when eggs of the frog are treated 

 with solutions containing both salts and sugar, as compared with 

 control solutions containing only salt or sugar. We have also tried 

 to compare the action of such sugars as cane sugar, that might 

 possibly invert, with the action of simpler sugars, like glucose or 

 lsevulose. We have kept in mind the possibility that while the 

 chief action of sugar is through its osmotic pressure, yet sugar 

 may also act chemically on the living substance ; or by forming 

 new compounds with the inorganic salts may affect the results in 

 this way. 



Action of Lithium Chlorid and Sodium Chlorid 

 Acting Alone. 



The concentration of LiCl that will prevent the development 

 from proceeding beyond the segmentation stages was previously 

 determined for the egg of Rana sylvatica to be about 0.65 per 

 cent. Since the salts obtained at different times may vary in the 

 amount of absorbed water, it was necessary (for percentage solu- 

 tions were used) to make a new determination as control for 

 exact comparisons with the effects of the new salt when united in 

 solution with sugars. The eggs were put into the solutions in 

 the 2-cell stages in all cases. It was found that in LiCl 0.5 per 

 cent, (the strength used in combination with sugar) the blastopore 

 appeared and sometimes closed almost normally ; usually it 

 formed a ring around or below the equator of the egg. Lithium 

 chlorid of this strength is, therefore, near the limit of inhibitory 

 effects but below that limit. Some solutions of this strength 

 were used with sugar solutions. 



The upper limit of NaCl was not accurately determined in pre- 

 vious work on the frog l and the results are not in harmony with 



1 Morgan, T. H., "Experiments with Frog's Egg," Biol. Bull., XI., 2, 1906. 



272 



