392 STUDIES IN GENERAL PHYSIOLOGY 



compare Figs. 114 and 115 he will notice that more cleavage- 

 cells are formed in the four sectors which lie between the 

 four large drops, and which contain the larger number of 

 small droplets at the periphery, than in the four sectors which 

 contain the large drops and a smaller number of small drop- 

 lets. This relation may be accidental, but I may be allowed 

 to state that when Fig. 114 was formed I expected from my 

 earlier observations precisely that type of cleavage which is 

 shown in Fig. 115. 



The cells formed at the periphery continued to divide, 

 while the center remained undivided. The two cells which 

 had first been perceived there disappeared again. The four 

 central drops became steadily smaller, and one of them broke 

 up entirely into small droplets, as if a slow emulsion took 

 place (Fig. 117, e). In this way the blastoderm changed, 

 within fifty minutes, from the condition shown in Fig. 115 

 into that shown in Figs. 11> and 117. Development then 

 ceased. The long exposure to lack of oxygen at a relatively 

 high temperature led to an early death of the germ. 



The phenomena shown in Figs. 112-17 are typical. The 

 exceptions which one encounters are connected with differ- 

 ences in the behavior of the small droplets of the strongly 

 refractive substance. In this connection I must mention the 

 fact that a small percentage of the eggs also showed segmen- 

 tation in the middle of the blastoderm. In these cases, 

 however, I usually (if not always) found that not only the 

 periphery, but the entire blastoderm, was studded with very 

 minute droplets immediately before cleavage. The large cen- 

 tral drops were then found to dissolve rapidly (emulsion ?). I 

 also found in rare cases, though, that only one sector of the blas- 

 toderm divided, while the rest remained undivided. In these 

 cases also the small refractive droplets were usually collected 

 in this sector. These facts all support the idea that the refract- 

 ive substance forms the membranes of the cleavage spheres. 



