ARTIFICIAL PropucTION OF NORMAL LARV® D811 
open question whether it was not caused by the salts of the 
serum. This constitutes about all the data existing at the 
time I started my experiments.’ 
I had in the meantime made my experiments on the 
effects of ions upon the rhythmical contractions of muscle, 
and reached the conclusion that by changing the ions con- 
tained in a tissue we can impart to it qualities which it does 
not ordinarily possess.’ I concluded that it might be pos- 
sible to produce blastulz, or even plutei, from an unfertilized 
egg by merely changing the ions in the egg. Such changes 
were possible in three ways: first, by altering the qualitative 
constitution of the sea-water without altering its total osmotic 
pressure; second, by altering its osmotic pressure by the 
addition of certain salts; and, third, by combining both 
methods. The last way led to positive results. 
I began my experiments with a study of the effects of 
various ions on the development of the fertilized egg. 
Il. THE EFFECTS OF VARIOUS IONS UPON THE FERTILIZED 
EGGS OF ARBACIA 
The eggs were fertilized in normal sea-water, and after 
five minutes were put into the various solutions. The 
greatest care was used with the eggs, and as little sea-water 
as possible was added to the artificial solution to be tested. 
The eggs were collected in vessels in such a way as to form 
a thick layer. One or two drops from a pipette gave all the 
eggs needed for an experiment. These two drops consisted 
chiefly of eggs with the minimum amount of sea-water. The 
volume of each of the artificial solutions was 100 c.c. 
One chloride in solution—In a 3n NaCl solution 10, 
20, and in one case 50 per cent. of the eggs began to segment. 
They very rarely reached the sixteen-cell stage. The majority 
1I should have mentioned also the observations made by R. Hertwig, that by 
adding strychnin to sea-water the eggs of the sea-urchin can be caused to show 
the first segmentation. [1903] 
2Part II, p. 518. 
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