41 



amount. The nucleolus enlarges perceptibly. Numerour chromatic 

 masses appear on the linin meshwork and gather close to the nuclear 

 wall. A later stage (size of nucleus, 4.0 microns) shows the chromatin 

 in the form of delicate spireme which at certain points appears dis- 

 posed as two parallel threads. The spireme grows stouter and con- 

 tracts in a tangled mass about the nucleolus. The contraction phase 

 or synezesis is complete in oocytes where the nucleus has a diameter 

 of about 5.0 microns. The disentangling of the spireme from synezesis 

 leaves the nucleolus intact and still intensely chromatic. The linin 

 meanwhile remains wholly achromatic. The stout spireme of this stage 

 appears moniliform. 



The oocyte of the first order now enters upon a period of very 

 rapid growth and the chromatin content of the nucleus undergoes 

 decided alterations. During the growth period the nucleus increases 

 20 diameters and the gain in volume of the egg cell and nucleolus 

 is approximately proportional. The spireme of postsynezesis soon 

 becomes double and segments transversely into a number of paired 

 beaded rods. These grow stouter and shorter, assume a mossy ap- 

 pearance, and pass through various transformations taking on ring, 

 V, and bilobed forms. During this period staining reactions give in- 

 'dications of a large amount of chromatin acattered over the linin net- 

 work. The nucleolus has now frequently a vacuolated appearance. 

 The chromosomßs may be traced through every stage of the growth 

 period. In the latter half of this period, they are found disposed in 

 one or several masses of minute bilobed bodies in various locations 

 in the nucleus. At the culmination of the growth period and shortly 

 prior to maturation the nuclear network is again completely achromatic. 

 The nucleolus is homogeneous and intensely chromatic. The chromo- 

 some group is usually in very close proximity or even superficially 

 attached to the nucleolus. 



In the living oocyte of this stage numerous vacuoles are seen in 

 the nucleolus. Similar vacuoles (always showing the orange G. stain) 

 are also seen in the nucleoli of the preserved eggs at certain stages 

 of their development. The increase in size of the nucleolus is effected 

 by the constant addition of chromatin. Staining reactions of the nuclear 

 reticulum show that the chromatin is transported along the linin fibers. 

 Various appearances indicate that the chromatin enters and leaves the 

 nucleolus in the form of viscid drops. The fact that the vacuolated 

 nucleolus (as seen in living material) appears homogeneous in the 

 stained material just prior to maturation is explained by the reasonable 

 assumption that the chromatin entering the plastin ground substance 



