Specificity in Fertilization 75 



sperm of Asterina only one per cent, could be fertilized. ^ 

 Godlewski succeeded by the same method in fertilizing 

 the eggs of a Naples starfish with the sperm of a crinoid. "" 

 The writer did not succeed in bringing about the ferti- 

 lization of the egg of another sea urchin in California, 

 Strongylocentrotus franciscanus, with the sperm of a 

 starfish. Although these eggs formed a membrane 

 in contact with the sperm, the latter did not enter the 

 egg ; nor has the writer as yet succeeded in causing the 

 sperm of Asterias to enter the egg of Arbacia. 



Kupelwieser^ observed that the spermatozoon of 

 molluscs may occasionally enter into the egg of S, 

 purpuratus in normal sea water and later, at Naples, 

 he observed the same for the sperm of annelids. In 

 these cases no development took place. In teleost 

 fishes the spermatozoon can enter the eggs of widely 

 different species but with rare exceptions all the embryos 

 will die in an early stage of development. ^ 



2. The fact that an increase in the alkalinity or in 

 the concentration of calcium allowed foreign sperm to 

 enter the egg of the sea urchin, suggested the idea that 

 a diminution of alkalinity or calcium in the sea water 



'Loeb, J., Arch. f. d. ges. Physiol, 1903, xcix., 323; 1904, civ., 325; 

 Arch. J. Entwcklngsmech., 1910, xxx., II., 44; 1914, xl., 310; Science, 

 1914, xl., 316. 



'Godlewski, E., Arch. f. Entwcklngsmech. , 1906, xx., 579. 



3 Kupelwieser, H., Arch. f. Entwcklngsmech., 1909, xxvii., 434; Arch, 

 f. Zellforsch., 19 12, viii., 352. 



4 See Chapter II. 



