9 



T. H. MORGAN. 



and no embryo develops. In a 12 per cent, solution the egg 

 reaches only the late cleavage stages. 



In a solution of LiCl 0.4 per cent, -f sugar 5.0 per cent, 

 only about the sixty-fourth-cell stage is reached. Thus to- 

 gether the two substances produce an effect that neither alone 

 affects. In another case, LiCl 0.5 per cent, -f sugar i.o per cent, 

 delayed the closure of the blastopore ; a solution of LiCl 0.5 

 per cent. + sugar 2.0 per cent, also delayed, but did not actually 

 prevent the closure of the blastopore ; while a solution of LiCl 

 0.5 per cent. + sugar 4.0 per cent, stopped the development of 

 most of the eggs in the late cleavage ; although in one case at 

 least the outline of the neural plate appeared. The results show 

 that the sugar reinforces the effects (or a part of it at least) of 

 the lithium. It remains now to see whether the results can be 

 explained as due to osmotic pressure alone or whether a chemical 

 effect also occurs. 



