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 as a rule. 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 



