268 CARL R. MOORE. 



membrane. It 'is therefore possible to assume that all eggs that 

 have segmented have been preceded by cortical changes of 

 some intensity at least. 



As one may see from Table I., the largest percentage of 

 cleavages obtained from an exposure to the weaker hypertonic 

 solution (Lot A) was 8 per cent, and that the greatest number of 

 swimming larvae was 2 per cent., therefore many of the eggs had 

 segmented that did not continue their development to the 

 swimming stage. The optimum effect of the solution for initia- 

 tion of development was not imparted to the eggs and develop- 

 ment ceased after a few cleavages. In the great majority of 

 eggs, however, no evidence of initiatory changes are discernible 

 and one would naturally suspect that they were yet capable of 

 fertilization, and this, as the experiment shows, is partially true. 

 The shorter exposure eggs when inseminated immediately after 

 return to sea-water, react quite normally with sperm, producing 

 a fertilization membrane, normal cleavage and a high percentage 

 of swimming larvae. But as the exposures are lengthened there 

 is a gradual decline of the normal conditions until an exposure 

 to hypertonic solution, sufficiently prolonged, will entirely pro- 

 hibit fertilization of the eggs. 1 After an exposure, lasting 25 to 

 30 minutes, to this concentration, the eggs begin to show a 

 tendency for loss of pigment: they are lighter in color and a few 

 are so affected as to be reduced to mere shadows of their former 

 condition, but this is much more true of the longer exposures. 



The character of cleavage and of larval development also 

 declines from the normal as the curve of fertilization approaches 

 zero. In the experiment cited, dishes A I and A 2 gave practically 

 normal cleavage and 85 per cent, to 95 per cent, of swimming 

 forms that appeared practically normal. Beginning with dish 

 A 3 however and extending throughout the series of exposures, 

 cleavage became less and less normal; the cleavage planes had 

 grown more indistinct and in many eggs division of the nucleus 

 had gone on while the cytoplasm remained unsegmented. Some 

 of the dishes presented such an indistinct lot of cleavages 

 that it was almost impossible to judge whether or not an egg 



1 Lack of fertilization after exposure to solutions of various salts, has been 

 pointed out by R. S. Lillie, 'n. 



