W. B. Kirhham — Maturation of the Eg a of the White Mouse. 77 



the guinea-pig (figs. 5 and 7 of his paper). In one there is a tri- 

 polar spindle, and in the other two separate spindles, lying at 

 opposite poles of the egg. The latter may be due to the fact that 

 this egg possessed two nuclei. Still another abnormality is an egg 

 (Text-fig. 8), Avhich, from its position near the center of the ovary, 

 is almost surely degenerating, whose first polar body has formed a 

 resting nucleus. In all probability resting nuclei occur normally in 

 the first polar body only in those very rare cases where the mitotic 

 division is complete, and each part gathers its chromatin into such 

 a form. 



Figure 7. — Ovarian egg ; showing two spindles, — an abnormal condition. This 

 egg may have had two nuclei, x 675. 



Figure 8. — Ovarian egg whose position in the interior of the ovary and the 

 presence of its sister eggs in the Fallopian tube indicate a degenerate condi- 

 tion. Within the egg appear the second polar spindle, and above it the 

 first polar body, with an abnormal resting nucleus, x 675. 



Plate V, fig. 11, shows an ovarian egg which is unusual in that it 

 has no zona pellucida, the egg and first polar body lying free in the 

 liquor folliculi. This condition is probably due to the solvent action 

 of the killing fluid, as mentioned by Rubaschkin (:05), since all the 

 ovarian eggs in this series are likewise naked, 



Second Polar Spindle (Pis. III-IV, figs. 5-9). — Immediately after 

 the constricting off of the first polar body, the 12 dj^ads left in 

 the egg are drawn into the equator of a new spindle, and split 

 longitudinally. The second polar spindle is formed in a position at 

 right angles to the radius of the egg, as described by Tafani ('89), 

 and usually lies near the first polar body. It is smaller than the first 



