ANTAGONISM BETWEEN SALTS AND ANESTHETICS 597 



fertilization-membranes and begin to cleave. This is true also 

 though to a less degree, of the eggs treated with the calcium- 

 or magnesium-containing solutions. The effects of after-treat- 

 ment with hypertonic sea-water show the difference between 

 such eggs and normal unfertilized eggs. Hypertonic sea-water 

 acting on normal eggs for this length of time has no apparent 

 effect, causing neither membrane-formation nor cleavage. Its 

 action on eggs previously treated with anesthetic-containing salt- 

 solutions is, however, definite and well-marked. Even those 

 eggs which, if left alone, show no signs of membrane-formation 

 or other change, begin development, and a considerable pro- 

 portion — though smaller than in the case of eggs with definite 

 fertilization-membranes — reach the blastula stage. Many, of 

 course, die before reaching this stage. Both the above series 

 and that of table 2 afford numerous instances of this kind. It is 

 clear that some physiological modification has been produced 

 in the eggs, of the same nature as that which normally leads to 

 membrane-formation, but insufficient by itself to produce this 

 effect. The eggs are, however, brought into a condition in which 

 they respond more readily to the action of the hypertonic sea- 

 water. The antagonistic effect of the anesthetic is thus only 

 partial; although no membranes are formed and there is no 

 external sign of change, the eggs are rendered more responsive — 

 or sensitized — to the subsequent action of the hypertonic sea- 

 water. Examination of the above and succeeding tables will 

 show that the proportion of eggs remaining unaltered after the 

 treatment with hypertonic sea- water is always small. A cer- 

 tain proportion, however, do remain thus unaltered, apparently 

 those in which the protective action of the anesthetic has been 

 most complete. Such variability is always observed, though its 

 precise basis cannot be defined as yet. Similar conditions are 

 seen in the eggs treated with 0.55 m KCNS containing calcium 

 or magnesium; these cations are decidedly more effective than 

 the anesthetics, as shown above, and of the two magnesium has 

 the greater action; always the great majority (>90 per cent) 

 of eggs treated with these solutions remain to all appearance 

 quite unchanged, and if fertilized the next day develop normally. 



