PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 421 



The black and red pigment cells can be distinguished 

 from each other, not only by their color, but also by their 

 form. The latter send out a large number of thin pseudo- 

 podia-like processes which are never found in the black pig- 

 ment cells. In the experiments on the effect of lack of 

 oxygen on the cardiac activity of the Fundulus embryo, it 

 was noticed that the originally dark yolk-sac gradually be- 

 came lighter in color when exposed to hydrogen for a long 

 time. The pigment cells can be observed very carefully 

 with the microscope, and I expected to observe the same 

 phenomena that Biedermann observed in frogs. This was, 

 however, not the case. It was found in the course of a series 

 of experiments that the dark pigment granules and the 

 black cells gradually disappear the longer the current of 

 hydrogen is kept up, and that the collection of the -pigment 

 in the center of the cell does not occur. 



The changes in the red pigment cells in lack of oxygen 

 are of a somewhat different nature. The lightening of the 

 color often occurs in this case also. Besides this, however, 

 the cells become smaller. The tips of the cell-processes 

 break off, remaining visible at first as tiny droplets, which 

 disappear later. As this process continues, the pigment 

 cells gradually become smaller. 



These changes remind one of the fact that certain dyes 

 become colorless when reduced. In our experiments it 

 might also be possible that the discoloration of the black 

 pigment is a result of a reduction, which does not occur in 

 the presence of atmospheric oxygen. 



XIII. CONCLUDING REMARKS 



It seems to me that the most important result of the 

 foregoing experiments consists in the proof which has been 

 brought forward that in certain cases at first molecular, 

 and later morphological, changes are brought about in cells 



