134 BERTRAM G. SMITH 



Sections afford no explanation of the faint dark spot or shallow 

 depression noted in surface views of the animal pole after the rup- 

 ture of the germinal vesicle and before the formation of the second 

 polar spindle. An actual depression overlying the first polar 

 spindle is rarely found in sections; if present in the living egg it 

 must be lost through shrinkage of the egg during the process of 

 preparation for sectioning by the paraffin method. 



The yolk granules immediately adjacent to the cytoplasm 

 surrounding the spindle are distinctly larger than at the same level 

 elsewhere; they are doubtless brought from a deeper situation by 

 the migration of the nucleus. 



The anaphase of the first polar spindle has not been observed, 

 and the first polar body has been found only in a state of degener- 

 ation, in conjunction with the second polar spindle. 



3. The second polar spindle 



The second polar spindle (see figs. 36-38) may be distinguished 

 from the first by the smaller amount of chromatin material, and 

 by the fact that a well-defined pit already noted in surface views 

 usually lies above it. This pit sometimes disappears in the late 

 anaphase of the spindle. 



The debris of the first polar body is usually found at the bottom 

 or sides of the pit, outside of the cell wall; in some cases fragments 

 of its chromatin are found mingled with the contact disc of the 

 first polar spindle. The chromatin fragments stain but faintly 

 with borax carmine. 



The contact disc of the first polar spindle has fused with the 

 thickening of the cuticle which overlies it. In the telophase of 

 the second polar spindle a new contact disc is formed which soon 

 fuses with the old. In some cases linin threads have been clearly 

 traced from chromosomes to the contact disc of the early second 

 cleavage spindle, thereby sustaining the view of the origin of the 

 contact disc set forth in the account of the first cleavage spindle. 



No second polar spindle has been found in any eggs of the two 

 females, (A) and (B), for which the occurrence of the first polar 

 spindle was tabulated. This indicates that the second polar 

 spindle is not formed until after the eggs have been for some time 



