PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 385 



FIG. 103 



FIG. 104 



of the peripheral cell-limits had already become invisible 

 (Fig. 106), and after another fifteen minutes nothing could 

 be recognized of the entire blastoderm except a collection of 

 droplets which had fused into larger drops (Fig. 107). In 

 the next two hours the latter only became more spherical, 



but otherwise under- 

 went no change (Fig. 



108). The germdisk 



was optically still less 



visible than in the 



unfertilized egg. It 



therefore required 



only thirty-five min- 

 utes after cleavage 



came to a stop, for 

 the complete liquefaction of the cleavage-cells of an eight- 

 celled blastoderm. It is scarcely necessary to mention that 

 the same process in various experiments took a little more or 

 a little less time. 



What we observe here is found in every 



such experiment upon Ctenolabrus eggs, the 



only difference being 



in the form and the 



arrangement of the 



droplets of the 



strongly refractive 



material, which at 



times may form a 



more perfect cast of 

 the old lines of cleavage than in the experiment described. 

 Even when the oxygen is driven out so slowly that the egg 

 has time to reach the sixteen- or the thirty-two-cell stage in 

 the stream of hydrogen, the same series of degenerative 

 changes occurs as soon as cleavage has come to a standstill. 



FIG. 105 



FIG. 106 



