PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 399 



previous papers that such eggs do not lose their power of 

 dividing even after being kept for three to four days with- 

 out oxygen. On the other hand, I noticed a collection of 

 the strongly refractive droplets in the furrows between the 

 cells in Fundulus eggs also. Our observations on the 

 mechanics of cell-division, therefore, seem to hold also for 

 the Fundulus egg, only that the material for the surface 

 layer of the Fundulus cells seems to be different chemically 

 from that of the Ctenolabrus cells in that the latter in the 

 lack of oxygen flows together into droplets, while the former 

 undergoes no such structural changes. 



On the other hand, the Fundulus egg is very sen- 

 sitive to carbon dioxide. If a current of carbon dioxide is 

 passed through the gas-chamber in which are contained the 

 freshly fertilized Fundulus eggs, not a single cleavage occurs. 

 Furthermore, the eggs which have resided for only four 

 hours in such a current of carbon dioxide have lost their 

 power of development for all time. This is of great impor- 

 tance in judging of the effects of lack of oxygen it points 

 to the possibility that the resistance of the protoplasm to 

 lack of oxygen is not so very different in the Ctenolabrus 

 egg from that in the Fundulus egg, and that only a second- 

 ary molecular change the disintegration of the surface 

 layer of the cells into a number of droplets brings about 

 a rapid destruction of the Ctenolabrus cells. 



This possibility is supported by another fact. I have 

 pointed out in an article, which I have already cited, the 

 remarkable indifference of the Fundulus egg to the concen- 

 tration of the sea-water. This year Professor W. W. Nor- 

 man made similar experiments in my laboratory upon the 

 Ctenolabrus egg. In these it was found that the Ctenolabrus 

 egg is almost as insensitive to an increase in the concentra- 

 tion of the sea-water as is the Fundulus egg. 



I should not like to conclude this section without adding 



