386 STUDIES IN GENERAL PHYSIOLOGY 



The question now arises whether this liquefaction or fusion 

 of the cleavage-cells occurs equally well and with the same 

 rapidity in every stage of development. As soon as the eggs 

 have reached the sixty-four- or the one-hundred-and-twenty- 

 eight-cell stage, the behavior toward lack of oxygen is some- 

 what different. While in an egg 



a ** r* which is in the eight-cell stage the 



" :../'}// * j-.r cells fuse in about one hour in the 



absence of oxygen, a liquefaction of 

 A "' the cleavage-cells also occurs in the 

 y e gg s i* 1 the sixty-four- and one- 



FIG. 107 hundred-and-twenty-eight-cell stage, 



but only at the periphery of the blastoderm, and even here 

 more slowly than in the cells in the 

 earlier stages of segmentation. The 

 droplets of the refractive substance 

 appear in the furrows, but they are] 

 smaller than in the eggs in an earlier 



stage of development, and it is for this 



,-,,-, ., , FIG. 108 



reason perhaps that large oil drops are 



formed less easily. Figs. 109-111 illustrate the process of 

 liquefaction in such an egg. The egg 

 was put into the gas-chamber at 2:25 

 o'clock while in the sixty-four-cell 

 stage. At this time its shape was 

 sketched with the camera lucida 

 (Fig. 109). The outlines of the cells 

 within the blastoderm are not shown. 

 The segmentation at first continued. 

 FIG. 109 At 4 o'clock liquefaction was very 



distinct at the periphery. It occurred in this way that in 

 individual cells at the periphery of the blastoderm the 

 outline at first becomes invisible, after which the entire 

 cell gradually disappears. Through this disappearance of the 



