656 STUDIES IN GENERAL PHYSIOLOGY 



sea-water might increase the motility or fertilizing power of 

 the spermatozoa. The contrary is, however, true. The 

 eggs of the same female were divided into two lots. The 

 one was put into normal sea-water, the other was exposed for 

 fifty minutes to a mixture of 70 c.c. sea-water + 30 c.c. 2^n 

 MgCl 2 . At about the same time the sperm of one male was 

 distributed into two solutions of exactly the same character. 



After fifty minutes the eggs that had been in normal sea- 

 water were divided into three portions. To the first portion 

 was added sperm from the normal sea- water; to the second 

 was added sperm that had been for fifty minutes in a mix- 

 ture of 30 c.c. 2^n MgCl 2 + 70 c.c. sea-water. To the third 

 portion no sperm was added; it was intended to serve as 

 control material. The result was as striking as could be 

 desired. While the eggs to which the sperm from the nor- 

 mal sea-water had been added developed without exception 

 into trochophores, not one egg developed in lot 2, to which 

 the MgCl 2 sperm had been added. The control eggs remained 

 likewise undeveloped. 



A number of the unfertilized eggs that had been in the 

 MgCl 3 for fifty minutes reached the trochophore stage. 



This experiment proves conclusively that the MgCl 2 solu- 

 tion annihilates or certainly diminishes the fertilizing power 

 of spermatozoa. In a previous series of experiments I had been 

 able to show that the same is true for the eggs of sea-urchins. 



In addition I convinced myself through microscopic ex- 

 aminations that the females used were not hermaphroditic. 



III. THE SPECIFIC EFFECT OF K IONS ON THE DEVELOPMENT 

 OF THE UNFERTILIZED EGGS OF CH^TOPTERUS 



The preceding experiments seemed to indicate that KC1 

 has a specific effect upon the development of the unfertilized 

 eggs of Chsetopterus. Mead had already found 1 that if -| per 



i MEAD, Biological Lectures, Woods Hole, 1898 (Boston : Ginn & Co.). 



