92 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
It is very characteristic that the eggs usually disintegrate 
not while they are in the hypertonic solution but after they 
have been put back into the normal sea-water. This agrees with 
the observation we made on the disintegration of the egg after 
membrane formation, namely, that this disintegration begins 
at the time of the first cell division. The hypertonic solution 
does not permit cell division, while the cell division begins in an 
irregular way after the eggs are transferred to normal sea-water. 
Such eggs disintegrate into little droplets. 
The unfertilized eggs do not suffer as quickly in the hyper- 
tonic solution as the fertilized eggs. In the unfertilized egg 
the hypertonic solution must first induce some parthenogenetic 
changes before it can produce its destructive action. 
5. We must in this connection consider an idea emphasized 
by various authors that the fertilized egg is more permeable 
than the unfertilized. On this assumption we might understand 
why the fertilized egg is more easily destroyed in abnormal salt 
solutions than the unfertilized egg. Leaving aside temporarily 
the fact that the fertilized egg is protected for some time against 
the action of the same agencies if its development is prevented 
by lack of oxygen, this idea meets with other difficulties. If 
this view were correct, the egg should be permeable for such 
substances as NaOH, and the fertilized egg much more so than 
the unfertilized egg. The observations of Warburg and Harvey 
to be mentioned later have definitely shown that this is not the 
case. But how are we then to explain such phenomena as the 
following? The egg of Arbacia possesses a red pigment. If 
fertilized and unfertilized eggs are put into an alkaline solution, 
eg., 50¢c.c. m/2 NaCl+le.c. m/2 BaCl+0.2¢.c. N/10 
NaOH, the fertilized eggs lose their pigment almost instantly 
while the unfertilized eggs keep it for a long time.!. The explana- 
tion lies probably in the fact that the alkaline solution comes 
into direct contact with the cytoplasm of the fertilized egg, 
1 Loeb, Biochem. Zeitschr., X XIX, 93, 1910. 
