PLATE 7 



EXPLANATION OF FIGURES 



37 to 40 (1146) The polar bodies are large and protoplasmic and contain 

 oil droplets (first polar body has dropped off in figures 39 and 40), showing that 

 they were extruded at the centripetal pole; after centrifuging ceased the cyto- 

 plasm and nuclei moved back to the present protoplasmic pole. 



41 (1145) The first polar body was formed normally before centrifuging 

 began; the second was extruded during centrifuging and is much larger than 

 normal and lies at a distance from the first. Cytoplasm and nuclei moved back 

 to the true animal pole after centrifuging and the egg continued to develop 

 normally. 



42 to 54 (1136) Centrifuged 30 minutes; fixed from 6 to 24 hours later. In 

 some cases the first polar body is normal and lies at or near the animal pole 

 (figs. 42, 47, 54) showing that it was formed before centrifuging; in all cases the 

 second polar body is much larger than normal and lies at some distance from the 

 animal pole, showing that it was extruded during centrifuging; and in all cases 

 cytoplasm and nuclei returned more or less completely to the animal pole after 

 centrifuging ceased and the further development is normal in most cases. Chro- 

 mosomes of a second polar body rarely give rise to a resting nucleus, showing 

 that a centrosome is necessary for this process. 



42 First polar body is normal and lies near animal pole; second is very 

 large and contains cytoplasm and oil, showing it was formed at centripetal pole. 



386 



