28 THE DEVELOPMENT OF THE CHICK 
Although the nuculeus (germinal vesicle of authors) may 
be excentriec in position in the youngest ovocytes, it always 
occupies an approximately central position in those slightly 
older. The nucleus increases in size with the growth of the 
cell-body; in the youngest ovocytes its diameter is about 9 ». and 
Ne Ros sy oes 
Iie. 7. — Section of an ovarian ovum of the pigeon; drawn from a prepara- 
tion of Mr. J. T. Patterson. The actual dimensions of the ovum are 1.44 
x 1.25 mm. 
f. s., Stalk of follicle. G. V., Germinal vesicle. Gr., Granulosa. L., 
Latebra. p. P., Peripheral protoplasm. pr. f., Primordial follicles. Th. ex., 
Theca externa. Th. int., Theca interna. Y. Y., Yellow yolk. Z.r., Zona 
radiata. 
in the ripe ovum it is flattened and measures about 117 x 
315 p. It retains its central position until the ovum is about 
0.66 mm. in diameter, and then moves to the surface where 
it hes almost in contact with the vitelline membrane (Fig. 
7). It becomes elliptical, and later the outer surface is flat- 
