594 STUDIES IN GENERAL PHYSIOLOGY 
experiment which led me in the right direction. In this ex- 
periment the following four mixtures were used: 
(1) 60 cc. 3°n MgCl, +40 c.c. of sea-water 
(2) 60 cc. 4¢n KCL + “ 
(83) 60 c.c. 432 NaCl + fs 
(4) 60 c.c. 4° CaCl, + ss 
A lot of unfertilized eggs were distributed in these four 
solutions, and remained in the same for one hour and fifty 
minutes. They were then brought back into normal sea- 
water. The eggs that had been in the first (MgCl, ) solution 
began to show an amceboid change of form (indicative of a 
segmentation) in about fifteen minutes after they were 
brought back into normal sea-water. About one in a thousand 
eggs were in this amceboid stage. One does not see such 
changes in the normal egg where the membrane limits the 
amceboid motions. Fifty minutes later one in a thousand 
eggs divided into 2 or 3 cells. The cells were of about equal 
size. About two and one-half hours after the eggs had been 
put back into normal sea-water about one egg in five hundred 
had segmented, and the segmentation had proceeded to the 
eight-cell stage, although not all the eggs had reached this 
stage. But then the development stopped. The next morn- 
ing the eggs were still without any membrane. All looked 
normal and healthy. In this experiment the volume of nor- 
mal sea-water into which the eggs were put after they had 
been in the MgCl, solution was small (only a watchglass full). 
Hence the few drops of the MgCl, solution which were 
transferred with the eggs modified the sea-water, and I 
think interfered with their development. It seemed to me 
that by avoiding this source of error, and by using large 
dishes with several hundred cubic centimeters of sea-water 
instead of the watchglass, it might perhaps be possible to 
see the eggs develop further. 
The eggs that had been in solution 2 (60 ¢.c. KC1+40 
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