No. I.] 



MVZOSTOMA GLABRUM. 



307 



nodules (Fig. 4). The nucleolus of the germinal vesicle remains 

 in the cytoplasm, as an inert mass, gradually melting away, but 

 not disappearing till about the 8-cell stage, when it may often be 

 found in the largest blastomere. This blastomere, I believe, 

 gives rise to the entoderm. Haecker has called attention to 

 a similar persistence of the nucleolus in the egg of ^quorea} 



In the first polar body spindle each chromosome separates 

 into its two rod-shaped halves, each half, which assumes the 

 shape of a Diplococcus, moving towards one of the poles. At 

 the poles the centrosomes have already divided. After the 



Fig. 3. Fig. 4. 



first polar body is constricted off, the second is speedily formed. 

 While the spindle of this polar body is in the equatorial plate 

 stage the chromosomes again split longitudinally and the cen- 

 trosomes again divide, so that two centrosomes go off with the 

 second polar body, and two remain in the ^%%. The first polar 

 body often begins to divide, but, so far as I have been able to 

 observe, its small spindle never gets beyond the equatorial 

 plate stage. The second polar body is always fully twice as 

 large as the first, and stains more deeply (Fig. 5). During its 

 protrusion the interzonal fibrils of the spindle are brought to- 

 gether in a sheaf-like bundle at the boundary line between the 

 cells, and there form a peculiar deeply staining plate, which 



Arch. f. mikr. Attat, Bd. 40, 1892. 



