174 Charles R. Stockard 



THE OSMOTIC EFECTS RESULTING FROM DEVELOPMENT IN SUGAR 



SOLUTIONS 



In order to be able to discriminate between the osmotic effects 

 and the effects of salt solutions it was necessary to make a careful 

 study of the manner in which the eggs reacted to the physical 

 changes; i.e.y to the osmotic pressures of the solutions. Loeb 

 ('94) had found that these eggs are "remarkably independent of 

 the concentration of the sea-water." He found that the embryos 

 develop in a perfectly normal fashion in fresh water as well as 

 sea-water to which five grams of NaCl had been added to each 

 100 cc. of water. When seven and one-half grams of NaCl were 

 added to each 100 cc. of sea-water a blastoderm was still formed, 

 but rarely an embryo. When twenty grams of NaCl were added 

 to 100 cc. of sea-water the power of development of freshly fertilized 

 eggs was annihilated within three or four hours. The only abnor- 

 malities that Loeb observed when eggs were in concentrated sea- 

 water were a shrinking of the yolks and a slower rate of develop- 

 ment. These experiments fail to show whether the effect is 

 osmotic or chemical, since by using NaCl one is dealing with a 

 chemical poison as well as increasing the osmotic pressure of the 

 solution. 



I have used sugar solutions prepared both in fresh and sea- 

 water to determine the effects of osmotic pressure on these eggs. 

 The sugar itself is supposed to exert slight if any chemical action. 



The eggs of Fundulus, since they develop normally in fresh 

 water, as recorded by Loeb ('02), Mathews ('04), the writer ('06), 

 and others, are evidently insensitive to the lowering of the osmotic 

 pressure of their surrounding medium. This is due probably in 

 part to the inorganic salts of this egg being held firmly in combina- 

 tion with its colloidal organic compounds in the protoplasm. 



Seven independent experiments were carried out with sugar 

 solutions in distilled water of the following strengths: 1.53 m, 

 1.33 m, i.o m, 0.66 m, 0.5 m, 0.33 m, and o.i6§ m. Solutions of 

 sugar in sea-water were used of the strengths i .33 m, i .0 m, 0.88 m, 

 0.66 m, 0.5 m, 0.33 m,and 0.16 m. A molecular solution of sugar 

 is equivalent to about a 31.4 per cent solution and exerts an 



