PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 387 



cells at the periphery the blastoderm becomes smaller (Fig. 

 110). At 6:35 o'clock the liquefaction of the cells at the 

 periphery had progressed much farther (Fig. 111). The 

 diameter of the blastoderm was only a little more than three- 

 fifths of the diameter the egg possessed four hours earlier 



when it was in the sixty-four-cell 

 stage. Around the blastoderm lay 

 granular masses, which were in all 

 probability the remains of the lique- 

 fied cells. Soon thereafter a change 

 (shrinking?) occurred in the yolk, 

 which served to close the experiment. 

 The disappearance of the cleavage- 

 cells occurs more slowly therefore in 



the later stages of development than in the earlier stages of 

 development. 



It may be of interest to raise the question: In what do 

 these peculiar structural changes consist which lead to the 

 fusion of the cleavage-cells in the absence of oxygen ? If 

 we wish to answer this question, we must acquaint ourselves 

 more fully with the history and the significance of those 

 peculiar refractive substances which appear in droplets. 

 Soon after fertilization, before the union 

 of the pro-nuclei, one observes in the center 

 and upon the surface of the germ the 

 appearance of several strongly refractive 

 droplets. These undergo, as has already 

 been said, a series of changes, of which 

 the most remarkable is this, that shortly 

 before the first cleavage a single system FIG - m 



of radiations coming from a common center is formed, which 

 looks very much like the radiations about a centrosome. 

 These radiations might be a process of emulsion, for the radii 

 break up very rapidly into small droplets which are strongly 



