ARTIFICIAL PRODUCTION or NORMAL LARV^: 581 



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. 1 



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. 2 I concluded that it might be pos- 

 sible to produce blastulse, 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. 



1 began my experiments with a study of the effects of 

 various ions on the development of the fertilized egg. 



II. 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 ^n 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 



i 1 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] 



2 Part II, p. 518. 



