PHYSIOLOGICAL EFrrerots or Lack oF OxyYGEN 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, 111 
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 
FIG. 110 
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