712 STUDIES IN GENERAL PHYSIOLOGY 



pressure of which is about equal to that of a |-m sodium- 

 chloride solution, 1 but also in distilled water, or in sea-water 

 the concentration of which has been doubled (by the addi- 

 tion of NaCl). In the following experiments, therefore, we 

 need not at all consider the osmotic pressure of the sur- 

 rounding solution. Secondly, since enormous numbers 

 of the eggs can be obtained, it is an easy matter to per- 

 form the experiments upon hundreds or thousands of eggs 

 at once. 



The eggs were artificially fertilized in the laboratory by 

 the addition of sperm, and then immediately distributed into 

 the various solutions. The embryo forms in from about 

 twenty-six to forty-eight hours varying with the tempera- 

 ture and twenty-four hours later the heart begins to beat, 

 and the circulation is established. Usually about two hun- 

 dred eggs were put into a solution, and after two or three 

 days the developed embryos were counted and the per- 

 centage of the eggs which had developed was determined. 

 The eggs were kept under observation as long as the 

 embryos remained alive. Usually when an embryo was 

 once formed, development went farther, and the circulation 

 was established. 



2. First of all the toxic effects of a pure sodium-chloride 

 solution at various concentrations were tested. In a ^ NaCl 

 solution every egg produced an embryo which died, how- 

 ever, before, or immediately after, emerging from the egg. 

 (The embryo hatches from between twelve to twenty days 

 after fertilization.) On the other hand, in a I m NaCl solu- 



/ ' o 



tion only a few of the eggs gave rise to embryos about Ito 

 5 per cent. In a -|ra NaCl solution an embryo forms but 

 rarely, and in a -| m NaCl solution the formation of embryos 

 is rendered impossible. The egg goes through the first 



lm represents that degree of dilution of a solution which contains one gram- 

 molecule of the substance in one liter of the solution. 



