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STUDIES IN GENERAL PHYSIOLOGY 



FIG. 112 



ture, it dies. If the experiment is interrupted early that 

 is, when the cell-walls have just begun to become indistinct 

 all, or at least a part, of the cell-membranes again become 

 visible upon admission of air. Under these circumstances, 

 however, every cell usually divides, not 

 into two, but into four cells which cor- 

 responds with what has been said before. 

 When we wait a little longer before 

 admitting air, a circular blastoderm is 

 at first formed in which no trace of cleav- 

 age is visible. The blastoderm then sud- 

 denly breaks 



up into a large number of cells at 

 once, but curiously enough this 

 cleavage is confined, in most cases, 

 to the periphery of the blastoderm. 

 In this case also the refractive sub- 

 stance which has been described 

 plays a peculiar r6le. Figs. 112- 

 17 represent 

 the various 



stages of the renewed cleavage of the 

 same blastoderm in which we studied 

 the disappearance of the lines of cleav- 

 age in hydrogen (Figs. 103-8). Fig. 

 108 shows the condition of the blasto- 

 derm in hydrogen at 2 : 10 o'clock. Only 

 four large drops of the refractive sub- 

 stance, surrounded by droplets of smaller 

 size, permit one to recognize the place 

 At 2:18 pure oxygen was sent through 

 the gas-chamber. At first the smaller droplets separated 

 from the surface of the large droplets and moved toward 

 what had been the periphery of the blastoderm. (Previously, 



FIG. 113 



FIG. 114 



of the blastoderm. 



