PLATE 11 



KXPLAXATION OF FIGURES 



55-58 Eggs in which the original polarity has been more or less modified. 



55 (1147) Centrifuged 4 hours, fixed 18 hours later. This figure may be 

 interpreted as follows: — The original animal pole was probably at the point AP 

 (the first polar body has been lost). The cytoplasm and second polar spindle 

 were carried away from this pole and a giant second polar body was formed 

 near the equator of the egg. Cytoplasm and nuclei did not return to the ani- 

 mal pole before the first cleavage (/) which was consequently equatorial, as in 

 figure 46. The micromeres formed from A and B are normal, though removed 

 from the original animal pole; those from C and D are abnormal though lying 

 at that pole. 



56 (1136, 5) Centrifuged 30 minutes, fixed 7 hours later. The first polar 

 body marks the position of the original animal pole, at which point two micro- 

 meres now center. The second polar body was formed at the vegetal pole as in- 

 dicated by the presence on it of the yolk lobe (yl). At the first or second cleav- 

 age the macromeres were partially separated and turned so that the poles at 

 which the micromeres form do not coincide in each quadrant except in quad- 

 rants A and B. Each macromere has formed one micromere which is normal 

 in size and appearance in quadrants A and C but which contains yolk in quad- 

 rants B and D. 



57 (1138) Centrifuged 30 minutes, fixed 12 hours later. At the upper side 

 of the figure is a large lobulated second polar body containing two masses of 

 chromatin and three centrospheres; it contains oil and cytoplasm and was ex- 

 truded at the centripetal pole. The two lower macromeres are partially sepa- 

 rated from the other two and contain but little cytoplasm and much yolk. Each 

 macromere has given off two micromeres which are abnormal in contents and 

 position in the lower quadrants but entirely normal in the upper ones, where the 

 micromeres of the first set are dividing. 



58 (1136, 4) Centrifuged 30 minutes, fixed 12 hours later. The first polar 

 body had formed at the animal pole before centrifuging; a giant second polar 

 body was then extruded at the vegetal pole. Afterward most of the cytoplasm 

 returned to the animal pole, but a portion remained at the vegetal pole, probably 

 cut off by an equatorial first cleavage as in figures 65 to 73. 



394 



