CELL DIVISION — SPINDLE IN SEA-URCHIN EGGS 229 



duce the same effect that fat solvents do, but in quite a different 

 way. Possibly low temperatures tend to precipitate the fat 

 globules out of the cytoplasmic emulsion. Such a precipitation 

 might produce an effect comparable to that of the lipoid solvents, 

 for either precipitation or solution would tend to remove the 

 lipoids from their emulsified state. If cold and lipoid solvents 

 both produce their effect by acting on the lipoids of the cell, it 

 is evident that these effects, instead of being complementary, 

 would be antagonistic. Actual experiment . demonstrated an 

 antagonism between cold and ether. Eggs treated both with 

 cold and ether showed less antigelatinizing effect than when 

 treated with cold alone or with ether alone. 



EFFECT OF INCREASED GELATION 



The preceding discussion was concerned with the effects of 

 various antigelatinizing agents upon the cytoplasm. It might 

 be interesting to mention briefly some other experiments with sub- 

 stances which tend to intensify the normal gelation. Many 

 authors have investigated the effect of hypertonic solutions on 

 dividing eggs. Loeb ('92) and Norman ('96) found that if the 

 hypertonic solution was sufficiently strong, cleavage was stopped. 

 Oftentimes, nuclear division without cytoplasmic division resulted. 



The effect of hypertonic solutions was investigated by the cen- 

 trifuge method, and in all c^es an intensified gelation could be 

 demonstrated. ^ Thk.i*'^ apparently especially marked in the cor- 

 tex of the egg, and^it is probable that such a cortical gelation is 

 the main factor which inhibits division of the cell, even when 

 the nucleus is still able to divide mitotically. 



July 5th. Eggs were fertilized at 10:43| a.m. At 11:08 a.m. some 

 of these eggs were placed in Stender dishes A, B, C, D, E. 



A contained 40 cc. sea-water plus 2 cc. 2^ N NaCl 

 B contained 40 cc. sea-water plus 4 cc. 2| N NaCl 

 C contained 40 cc. sea-water plus 6 cc. 2^ N NaCl 

 D contained 40 cc. sea-water plus 8 cc. 2| N NaCl 

 E contained 40 cc. sea-water plus 10 cc. 2| N NaCl 



