The Influence of External Factors on Developjnent 175 



osmotic pressure of 22.4 atmospheres. The osmotic pressure of 

 the sea-water at Wood's Hole, as determined by Garrey ('05) is 

 21.918 atmospheres, thus being nearly equivalent to a gram mole- 

 cular solution of sugar. 



DISTILLED WATER SOLUTIONS OF SUGAR 



Several of the sugar solutions employed exert an osmotic pres- 

 sure lower than that of sea-water, yet owing to their high specific 

 gravity the eggs float on them. We may first consider only the effects 

 induced by the 1.53 m, 1.33 m and the i.o m solutions. Two 

 hours after being in the 1.53 m and the 1.33 m solutions the yolks 

 have shrunken in a peculiar way, being circular in outHne when 

 viewed from above and oval when seen from the side, having such 

 a form as a plastic sphere would assume if pressed between two 

 horizontal planes. In the molecular solution the yolk does not 

 show this effect to any considerable degree and the rate of develop- 

 ment is slightly ahead of the control. After about twenty-three 

 hours all of the eggs in the 1.53 m sugar solution are dead, the 

 membranes of many have burst and allowed theyolk to stream out, 

 while in others the yolk is a small contracted and concentrated 

 mass. At this time many eggs in the 1.33 m are also dead, 

 although the few still alive are further advanced than the control, 

 the blastoderm lies flat on the yolk and the germ-ring is further 

 down. Those twenty-three hours old in the molecular solution 

 are alive and the germ-ring is further over the yolk than in the con- 

 trol. The osmotic pressure of the molecular solution should be 

 about 22 atmospheres which is almost equivalent to the pressure of 

 sea-water, that of the 1.33 m is 26.2 atmospheres, only four atmos- 

 pheres higher; while the 1.53 m has a pressure of 34.278 atmos- 

 pheres or about twelve atmospheres above the pressure of sea- 

 water. Eggs in the latter solution are seen to be fatally affected 

 within twenty-four hours. We meet here with the same peculiar 

 problem that I find in looking over Madame Rondeau-Luzeau ('02) 

 and Morgan's ('06) results. They found theupper limit of NaCl on 

 frogs' eggs to be about 2 per cent, which exerts a pressure of 13.61 

 atmospheres, while Morgan found the upper limit for cane sugar to 

 be 12 per cent, with a pressure of 8.376 atmospheres. I have found 



