EXPERIMENTS WITH FROGS EGGS. 



9 1 



In the accompanying table, kindly prepared by Dr. H. \Y. 

 Berg, the osmotic pressures of most of the solutions given in the 

 preceding statement are given. It will be seen for the upper limit 

 of Lid, namely, 0.65 per cent., the osmotic pressure is 6.161. 

 In comparison the results with NaCl are very different. The 

 upper limit is above 2 per cent. The osmotic pressure for 2 per 

 cent, is 13.61, which is more than double the strength of effective 

 LiCl. The comparison shows that the effects of the lithium salt 

 are not due to osmotic pressure alone. 



In a double solution containing LiCl 0.5 4- NaCl 0.5 nearly 

 normal embryos appeared, and the osmotic pressure in this case 

 is 8.33, which is much greater than that for the lithium alone. 

 It took, in fact, a solution containing LiCl o. 5 4- NaCl i.o to pre- 

 vent gastrulation. The osmotic pressure in this case is 11.76, a 

 pressure far greater than that for the effective limit of LiCl alone. 



The upper limit for cane sugar was found to be about 12 per 

 cent., which corresponds to an osmotic pressure of 8.376. This 

 is much higher than for the lithium chlorid alone. 



For solutions of LiCl 0.4 4- sugar 5.0 per cent., only the 64- 

 cell stage was reached. The osmotic pressure is 7.33, which is 

 again much higher than for lithium chloride alone, but less than 

 that for the sugar alone. It would seem, therefore, that the 

 two together must have a higher pressure than for the one 

 producing its effects at the lower limit, but less than for the 

 other that produces its effects at a higher pressure. Similar 

 conclusions might be drawn from the double solution con- 

 taining LiCl 0.5 4- sugar 4.0 per cent. The results show that 

 there is a double effect produced by salt solutions, a chem- 

 ical and an osmotic. How each effect is produced we do not 

 know at present. Loeb has shown, however, that living sub- 

 stances behave very differently towards the amount of water ab- 

 sorbed according to what chemical element, sodium, calcium, or 

 lithium, for example, that they have taken up. Since the devel- 

 opment of the embryo is associated with the amount of water 

 absorbed it might appear that in this way the chemical action is 

 similar to the results produced by means of osmotic pressures 

 which also effect the amount of water. That the egg contains 

 enough water in itself for normal development is shown by my 



