EXPERIMENTS ON CLEAVAGE 259 
described by Fol. In my experiments the eggs were impreg- 
nated under normal conditions, and cases of polyspermia were 
very rare indeed. Nearly all of the eggs which remained in 
normal sea-water segmented quite normally. But I thought 
of the possibility that new spermatozoa might enter the 
impregnated egg in the concentrated solution. I knew that 
such a supposition was in contradiction with all known facts, 
but these facts are still meager. If a polyspermia in my 
experiments took place, it could happen only in the concen- 
trated solution, as here the increase of the number of the 
nuclei was observed. But I found that the spermatozoa were 
perfectly paralyzed as soon as they were brought into the con- 
centrated solution; that is, in the sea-water to which 2 g. of 
NaCl to 100 c.c. had been added. I could show, moreover, 
that in this concentrated solution no impregnation is effected. 
I brought unfertilized eggs into this concentrated solution and 
added spermatozoa, When I brought them back into nor- 
mal sea-water, it took more time from that moment until seg- 
mentation began than it took in normal eggs and in normal 
sea-water from the moment of impregnation to the moment 
of segmentation. The spermatozoa contained in the concen- 
trated salt solution became active again a few minutes after 
being brought back into normal sea-water and then entered 
the eggs. Polyspermia in this case could be observed, but 
not asarule. Most of these eggs segmented into two cells. 
But it was astonishing how soon the spermatozoa lost their 
power of impregnating under these circumstances. Sperma- 
tozoa which had been in the concentrated solution only a 
few hours, when brought back into normal sea-water fertil- 
ized only a thousandth part, or still less, of the normal eggs; 
while spermatozoa of the same animal which had remained 
in normal sea-water fertilized at the same time practically all 
the eggs of the same female. When I tried to fertilize eggs 
in normal sea-water which had been in the concentrated 
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