322 MARGARET C. MANX. 



LITERATURE AND DISCUSSION. 



The observations upon atretic and unfertilized tubal eggs of 

 mammals agree essentially but the interpretations are rather 

 various especially with regard to atretic eggs. This is easily 

 comprehensible since no natural method of sedation is provided 

 in atretic material. On the other hand one can easily determine 

 the position of tubal eggs in the oviduct, and as these data show, 

 can then demonstrate that such eggs pass thru a regular series of 

 changes as they descend the duct. 



In eggs which are liberated into the fallopian tube the second 

 maturation spindle sometimes rotates to a position at right angles 

 to the surface. The dyads also divide occasionally so that the 

 second anaphase really appears to begin in some unfertilized 

 eggs. In by far the greatest number of eggs in the upper third of 

 the oviduct, however, the second polar spindle is parallel to the 

 periphery and intact, with the dyads still in late prophase posi- 

 tion. The spindle may or may not be somewhat broken. Xo 

 cytoplasmic changes were noted at this stage. In eggs in two 

 oviducts the spindle was central in position. 



Three of the facts cited above might be interpreted as indica- 

 ting that the cell processes may not all be wholly degenerative at 

 this stage. Firstly, the spindle may rotate as if in preparation 

 for the second polar division. Secondly, some of the dyads may 

 divide, and thirdly, the spindle may be found in the center of the 

 e gg- Eggs with central spindles all showed one of two degener- 

 ative conditions; the chromatin simply clumping into a single 

 mass and the cytoplasm shrinking and becoming denser, or in 

 other cases the cell wall may break and the very vacuolate 

 cytoplasmic contents scatter. There is no indication in the tubal 

 rat material that normal cleavage ever occurs in these eggs altho 

 it may of course be possible that more material might include 

 such stages since a few eggs give the appearance of approximately 

 normal early cleavage stages. In by far the greatest number of 

 eggs degeneration begins with the failure of the second polar 

 division. It is of some interest that the formation of but one 

 polar body is a characteristic feature of development of nn>-t 

 naturally parthenogenetic animal eggs. 



Degeneration has been shown to begin with the breaking "I the 



