DEVELOPMENT OF THE FROG S EGG. 275 



The upper limit for this combination lies therefore about NaCl 

 0.5 per cent, plus 3.0 per cent, glucose. 



The Action of Sugar Solutions. 



The experiments with sugar solutions were conducted to find 

 if possible an explanation of the peculiar results which Stockard 

 had obtained during the past summer by treating Fundulus 

 eggs with solutions of sugars and sugar and salt mixtures. 

 When Fundulus eggs were subjected to a solution containing LiCl 

 or NH 4 C1 and cane sugar the action of the salt was greatly aug- 

 mented by the presence of the sugar even though the osmotic 

 pressure of the mixture was lower than that of sea water. This 

 indicated that the more marked action was not due to any in- 

 crease in osmotic pressure that may have resulted from the addi- 

 tion of the sugar, but to some further or new chemical action. 



Equal amounts of sugar were found to exert a more injurious 

 effect on Fundulus eggs when in fresh water than when in sea 

 water, although obviously the osmotic pressure of the latter was 

 much the greater. This seemed possibly to indicate that the cane 

 sugar in the fresh water solutions had become inverted, thus 

 producing these pecular results. From a consideration of the 

 experiments below it would seem more probable, however, that 

 sugar exerted some chemical action on the compounds of the 

 egg when in fresh water solutions rather than that inversion had 

 taken place resulting only in an increase of pressure. 



Frog eggs when in the four-cell stage were subjected to the fol- 

 lowing solutions of cane sugar : 6, 8,9, 10, 11,12, 12.5, 13, 15, 

 17 and 20 per cent. Although this is a series of fairly wide range 

 it was found that the eggs were only slightly affected in the 6 per 

 cent, solution, while they reached a late segmentation stage even 

 in the 1 5 per cent, solution ; the limit of effectiveness or fatal 

 dose of sugar is thus seen not sharply indicated as in the case of 

 many salts where a small fraction of a per cent, difference in the 

 concentration of the solution gives at the critical points a marked 

 difference in the effects on the eggs. The specific gravity of the 

 sugar solutions was so high in most cases that the eggs would 

 float in an indifferent position, the greater weight of the yolk pole 

 not serving as it normally does to orient the egg in a definite 



