374 STUDIES IN GENERAL PHYSIOLOGY 



without oxygen, we are inclined to imagine that the given 

 organ or organism lacks the necessary energy for performing 

 this function. If we remember, however, that the conver- 

 sion of chemical into the physiological function depends 

 upon definite molecular conditions in the cells (state of mat- 

 ter, osmotic pressure, surface tension, phenomena of spread- 

 ing, etc.), another explanation is possible, a priori: the cells 

 are still able to produce the energy necessary for the physio- 

 logical functions of the organ, but lack of oxygen led to 

 molecular changes in the cells which prevented the conver- 

 sion of the chemical energy into mechanical or other forms 

 of energy. So far as I know, there are as yet no facts at 

 hand to support such a view. Yet the following experi- 

 ments, I believe, have led to positive results in this direction ; 

 for we can show that the eggs of Ctenolabrus and sea-urchin 

 cannot segment without oxygen, and that, moreover, the 

 already formed cleavage-cells of these eggs, especially those 

 of Ctenolabrus, undergo certain structural changes when 

 deprived of oxygen, which cause the cells to fuse together. It 

 is possible that in this case we deal with a liquefaction of the 

 membrane or the specific surface film of the cleavage-cells, 

 and furthermore that the impossibility of the formation of a 

 membrane in the absence of oxgen is why no cleavage occurs 

 under these conditions. But no matter what one may 

 assume regarding the formation of a membrane, it is clear 

 that when separate cells fuse in the absence of oxygen, it is 

 not to be expected that the unsegmented egg will be able to 

 divide under these conditions. But those cells which have 

 fused are by no means dead. When they are again supplied 

 with air, segmentation sets in anew. We therefore see that 

 the structural changes resulting from the absence of oxygen 

 suffice to explain the failure of segmentation, and that it is 

 not necessary in this case to attribute the latter to a failure 

 of the source of chemical energy. This conclusion is further 



