218 MEAD. 
EXPLANATION OF PLATE XIX. 
Fic. 46. First cleavage-spindle in the metaphase. Chromosomes moving 
towards the poles, with nucleoli left in the middle between them. Centrospheres 
at the height of their development. 
Fic. 462. Late anaphase. The centrosphere at left shows the destructive 
action of corrosive-acetic acid. 
‘Fic. 47. Two adjacent sections combined. One shows the centrosphere and 
two brown-black centrosomes with central spindle between them; the other, the 
eighteen chromosomes, black, belonging to the larger aster. The smaller aster 
showed the same features. 
Fic. 48. First cleavage-spindle in the beginning of telophase ; chromosomes 
commencing to swell up into vesicles. Nucleoli, z., centrospheres, and centro- 
somes as in the two previous figures. 
Fic. 49. Spindle in the telophase ; chromosomes vesiculated ; fibres in the 
middle of spindle very distinctly varicose and bent; nucleoli in the midst of 
spindle. Centrospheres completely resolved so that the rays diverge from the 
centrosomes directly and are again very extensive, many of them reaching the 
periphery of the egg. Yolk-lobe, y.2. 
Fic. 50. Transverse section through the larger cell a little later than the pre- 
ceding figure. Yolk-lobe, y.2. Two adjacent sections combined as in Fig. 47. 
The two centrosomes with central spindle between them. Eighteen chromatic 
vesicles. 
Fic. 51. Reconstitution of the nuclei. Only one of the two centrosomes in 
either cell is visible in this section. Middle-plate, z., in many pieces from each of 
which diverging fibres extend to the nuclei. Nucleoli or first cleavage-nucleus 
remaining in larger cell, z. 
Fic. 52. Three consecutive sections, I, 2, 3, combined: z., Zwischenkorper; 
z., nucleoli of first cleavage-nucleus; 2.1, nucleoli in new nucleus. Both centro- 
somes visible in either cell. 
Fic. 53. Smaller of the two cells with resting nucleus. Two asters on oppo- 
site sides of nucleus; centrosomes, centrospheres, and comparatively short rays. 
Fic. 54. Transverse section of one of the two cells. Nuclear membrane 
breaking down. Cytoplasmic network; nuclear network; chromosomes, cd. ; 
nucleolus, .; two centrosomes and central spindle. 
Fic. 55. Transverse section of one of the two cells. Prophase of the 
second cleavage-spindle ; chromosomes, c4.; nucleolus x. 
Fic. 56. Beginning of the metaphase, 2-cell stage. Chromosomes in both 
centrospheres dividing. 
Fic. 57. Transverse section of the smaller of the two cells. Chromosomes 
undergoing heterotype splitting ; centrosomes distinctly separate. 
Fic. 58. Transverse section of the larger cell of the same egg as Fig. 57. 
Spindles slightly further advanced. Centrosomes at a considerable distance 
apart in both asters. 
