622 BULLETIN OF THE 



Fig. 59. Yolk of exceptional form. The primitive axis lies in tlie plane of the 

 optical section. The pronuclei, male and female, have attained considerable size, the 

 latter still united to the polar globule by interzonal filaments. About midway between 

 the pronuclei a dense, but less granular area, around which the yolk granules show a 

 radial arrangement, — the senescent internal aster of the second archiamphiaster. 

 The region of this aster is more deeply stained than the surrounding yolk. Another 

 region of crescentic form appears in the vegetative half of the yolk beyond the male 

 pronucleus, and is likewise deeply stained. It is represented in the figure by deeper 

 shading. 



Fig. 60. Optical section oblique to the primitive axis. Polar globule "pro- 

 jected." Male and female pronuclei, the latter distinct -from the central area of the 

 internal half of the second archiamphiaster. 



Fig. 61. Equatorial optical section. Polar globules, pedicel, lateral zone of thick- 

 enings, granules of astral area, and short stout rays of aster, projected. Granulation 

 of the yolk omitted. A sufiicient difference in the prominence of the long and 

 the short rays has not been observed in lithographing. 



Fig. 62. Meridional optical section of same, the first polar globule being omitted. 

 Lateral zone and areal corpuscles more nearly approximated than usual. 



Fig. 62*. Living egg near the close of the first segmentation. Consult the text 

 at p. 223. 



Fig. 63. Female pronucleus small, homogeneous, lying at the border of the cen- 

 tral area of the internal aster. The "interzonal filaments" exhibit a plate, pp (the 

 Zellplatte ?), near the point of their deepest constriction. The areal corpuscle of the 

 external aster fused with the envelope of the polar globule at its distal pole. Osmic 

 acid preparation. 



Fig. 64. The second polar globule of the same egg seen from the animal pole. 

 Osmic acid preparation. 



Fig. 65. The male and female pronuclei in the living egg. 



Fig. QQ. Formation of the second polar globule; "interzonal filaments" bent 

 nearly at right angles (compare Fig. 19) ; the spiral rays of the internal aster radiate 

 from a spiral line, o )8 ; the areal corpuscles and the thickenings of the internal zone 

 not distinguishable from each other ; two vesicular structures in the vegetative hemi- 

 sphere — incipient male pronuclei (?) — do not contain nucleolar corpuscles. 



Fig. 67. Portion of the same egg seen after rotating the yolk 90° about the 

 primitive diameter as an axis. The internal end of the spindle is deeply stained, but 

 not sharply defined. 



PLATE IV. 



Fig. 68. Second polar globule with nucleus, and longitudinal folds in the en- 

 velope of its pedicel. The position of the vitelline half of the " interzonal filaments " 

 is indicated by a streak of non-granular protoplasm extending to the female pro- 

 nucleus, in which, however, filaments are not traceable. Both pronuclei pear-shaped, 

 with the sharper ends (not outlined with sufficient distinctness) directed toward the 

 centre of a clear spot which is surrounded by numerous faint rays, — the senescent 

 internal aster of the second archiamphiaster. The pronucleoli more numerous in 

 the female (25) than in the male (20) pronucleus. Osmic acid preparation. 



Fig. 69. Oblique view of the formative pole of the yolk (the two polar globules 



