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HELEN DEAN KING. 



of membrane which form the outer covering of the egg. These 

 cells, which are usually oblong in shape, contain a small amount 

 of faintly staining, granular protoplasm, and a very large, rounded 

 nucleus with one nucleolus. The chromatin is either collected in 

 masses along the nuclear wall, or it is in the form of a more or 

 less regular network scattered throughout the nucleus. 



Ordinarily, when the egg of Bnfo lentiginosus is ready to leave 

 the ovary, it has a diameter of about 1.5 mm. and from 0.60-0.70 

 mm. of its surface is in contact with the outer membrane of the 

 ovarian wall (Fig. i). In the great majority of cases, the egg 

 is attached at the equatorial region as in Fig. I ; but it is not un- 

 common to find among the eggs thus attached, one with its 

 black or its white pole against the outer membrane. 



Z P 



-Y 



FIG. 2. Part of an ovarian egg highly magnified, showing the structure of the 

 membranes surrounding the egg. C, blood corpuscle; Y, yolk ; Z.P., Zona pellu- 

 cida. Zeiss apoc. 2 mm. Oc. 8. 



By what means the ovarian wall is ruptured and the eggs set 

 free into the body cavity is not known. This process cannot be 

 connected with the breaking down of the germinal vesicle, because 

 the nucleus degenerates and the first polar spindle is formed some 

 time before the egg leaves the ovary, as I have shown in a pre- 

 vious paper (2) ; neither can it be due to the way in which the 

 eggs are attached to the ovarian wall, for, as I have stated above, 

 the mode of attachment varies with individual eggs. Apparently 

 the eggs must reach a definite stage of development before they 

 break away from the wall of the ovary, because, although I have 



