Specificity in Fertilization 



81 



and ovaries had been kept in NaCl and all the sperm 

 was immotile. Eggs and sperm were mixed together 

 in a pure m/2 NaCl solution where the sperm was 

 only rendered motile by the proximity of eggs. The 

 following table gives the result. x 



TABLE V 

 SPECIFICITY OF ACTIVATION OF SPERM BY EGGS 



The spermatozoa of starfish show a marked speci- 

 ficity inasmuch as they are strongly activated only by 

 the eggs of their own species, although in this experi- 

 ment these were immature, and to a slight degree only 

 by the eggs of the sea urchin purpuratus. But it is 

 also obvious that the specificity is far from exclusive 

 since the immature eggs of Asterina activate the sperm 

 of the sea urchin franciscanus as powerfully as is done 



1 Loeb, J., Am. Naturalist, 1915, xlix., 257. 



