ARTIFICIAL PRopDUOTION OF NormMaL Larvee 595 
c.c.sea-water) also began to segment. The next morning about 
1 per cent. of the eggs were divided into from 2 to 4 cells. 
They were all without membranes, but they looked less normal 
than the MgCl, eggs, and soon began to disintegrate. 
The third lot of eggs had been in 60 c.c. NaCl -+- 40 c.c. 
sea-water. Practically none of these eggs segmented during 
the next twenty-four hours, and none formed a membrane. 
The fourth lot of eggs had been in 60 c.c. CaCl, + 40 cc. 
sea-water. A few of these showed a beginning of segmen- 
tation, but every egg had a membrane. I have found since 
that in pure CaCl, solutions of even lower concentration 
unfertilized eggs form a membrane. It is possible that the 
formation of a membrane consists in a process of coagula- 
tion which is favored by Ca ions.’ 
I made a parallel series of experiments with fertilized 
eggs of the same female. The eggs were, as usual, fer- 
tilized in normal sea-water, and five minutes later were put 
into the various solutions. The eggs were divided into 
four lots, and put into solutions of the same character as in 
the above-mentioned experiment with unfertilized eggs. 
Like the unfertilized eggs, the fertilized eggs remained in 
the solution one hour and fifty minutes. When brought 
back into normal sea-water those that had been in solu- 
tion 1 (60 c.c. MgCl, + 40 c.c. sea-water) began to divide in 
fifteen minutes. The segmentation was very regular. Two 
hours and forty-five minutes later every egg was segmented 
into from 8 to 32 cells. Every egg had a membrane. The 
next morning a large number of eggs swam about in the 
blastula stage, still having a membrane. This observation is 
of importance, as it shows that even in eggs that were in a 
mixture of 60 c.c. %°n MgCl, with 40 c.c. sea-water the 
1 Hertwig showed that unfertilized eggs form a membrane in water saturated 
with chloroform. Herbst found that benzol, toluol, and xylol bring about the same 
effect. Allthese media havea coagulating effect. Hrrsst, Biologisches Central- 
blatt, Vol. XIII (1892), p. 14. 
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