THE PROCESS OF FERTILIZATION. 277 



experiment on the unfertilized eggs of the sea urchin, and found 

 that the unfertilized egg, if treated for several hours with con- 

 centrated sea water, was able to show the beginning of a seg- 

 mentation when put back into normal sea water. A small 

 number of eggs divided into two or four cells, and, in a few 

 cases, went as far as about sixty cells, but no larva ever devel- 

 oped from these eggs. (4) Morgan had used the same concen- 

 tration of sea water as Norman (5) and I had used in our 

 previous experiments. I had added about 2 grams of sodium- 

 chloride to 100 c.c. of sea water. Norman used instead of this 

 3/^ grams of MgCU to 100 c.c. of sea water, and Morgan used 

 the same concentration. Mead made an observation somewhat 

 similar to Morgan's upon Chaetopterus. He found that by 

 adding a very small amount of KC1 to sea water he could force 

 the unfertilized eggs of Chaetopterus to throw out their polar 

 bodies. The substitution of a little NaCl for KG did not have 

 the same effect. (6) While continuing my studies on the effects 

 of salts upon life phenomena, I was led to the fact that the 

 peculiar actions of -the protoplasm are influenced to a great 

 extent by the ions contained in the solutions which surround 

 the cells. As is well known, if we have a salt in solution, say 

 sodium-chloride, we have not only NaCl molecules in solu- 

 tion, but a certain number of NaCl molecules are split up into 

 Na ions (Na atoms charged with a certain quantity of posi- 

 tive electricity) and Cl ions (Cl atoms charged with the same 

 amount of negative electricity). When an egg is in sea water, 

 the various ions enter it in proportions determined by their 

 osmotic pressure and the permeability of the protoplasm. It 

 is probable that some of these ions are able to combine with 

 the proteids of the protoplasm. At any rate, the physical 

 qualities of the proteids of the protoplasm (their state of matter 

 and power of binding water) are determined by the relative 

 proportions of the various ions present in the protoplasm or in 

 combination with the proteids. (7) By changing the relative 

 proportions of these ions we change the physiological properties 

 of the protoplasm, and thus are able to impart properties to a 

 tissue which it does not possess ordinarily. I have found, for 

 instance, that by changing the amount of sodium and calcium 



