Eugene Howard Harper 9 



Some Late Stages of the Ovarian Egg. 



The growth of the ovarian egg may be roughly divided from one point 

 of view into two periods. The first is a long one of very slow growth, 

 the second is a short period in which the main increase in size of the 

 egg is effected. Two eggs mature at a time, occasionally only one. The 

 second pair in order of development are usually quite small, the larger 

 being ordinarily several millimeters in diameter when the first pair are 

 mature, but it may be half-grown occasionally at this time. 



The full-sized egg in its capsule is nearly an inch in diameter. In 

 Fig. 1 is shown the nucleus of an egg 1.4 mm. in diameter. It measures 

 338/A in diameter, and, being nearly spherical, is greater in volume than 

 the nucleus of ^ egg which was in the midst of its rapid growth and 

 15 mm. in diameter. The latter nucleus is lens-shaped, flattened against 

 .the follicular envelope, and its diameter is 378/^ (Eig. 3). In a smaller 

 egg 12 mm. in diameter the nucleus is shown in horizontal section 

 (Eig. 3b). Its greater diameter is 339/;i. The ground substance of the 

 nucleus or germinal vesicle is of a finely alveolar character, appearing 

 under a low power to contain only a few scattering deutoplasmic granules. 

 Under a higher power, however, it is seen to be thickly studded with 

 microsomes of the same character as the larger granules. The chromo- 

 somes are in a group in a somewhat eccentric position, surrounded by a 

 system of radiations. Apparently pairs of dumbbell-shaped dyads are 

 lying side by side. They are unequal in size, three of the pairs being 

 considerably larger. Two of the pairs are crossed, lying very close 

 together (Eig. 17). There are numerous glistening refractive bodies 

 scattered among the chromosomes, some small and some in vesicular 

 masses. At the center of the germinal vesicle is a considerable amount 

 of chromatic staining material in the form of short threads, and also a 

 group of rounded bodies like nucleoli lying underneath them. The 

 nucleoli in some cases have short remnants of chromatic threads clinging 

 to them. 



A later stage is shown in Eigs. 4a and b. In Eig. 4a the whole ger- 

 minal area of this egg is shown, the germinal vesicle enlarged in Eig. 

 4b. This egg was the older of a pair, the nucleus of the younger of 

 ■which is shown in Eig. 3. A comparison of the size of the nuclei shows 

 a great diminution. The wall of the nucleus is seen to be breaking 

 down. Its contour is no longer regular, but it has shriveled up and 

 retreated from its manifestly former position. The disintegrating wall 

 is surroimded by a zone of the nuclear ground substance. The diameter 

 to the outer limits of this zone is 310/*, showing an invasion of the yolk 



