Plate IX 



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a 



. 



* 



c d 



Four stages in the production of polar bodies in the egg of the Mollusc Physa 

 fontinalis. From KOSTANECKI and WIERZEJSKI. 



a. Anaphase of first polar mitosis ; on the right, sperm head with aster appearing in 

 front of it. 



b. Telophase of first polar mitosis ; polar body being extruded. Below, head and tail 

 of spermatozoon. 



c. Metaphase of second polar mitosis ; first polar body completely extruded. Below, 

 sperm aster with divided centrosome widely separated from sperm head. 



d. Telophase of second polar mitosis, and extrusion of second polar body. 

 All the figures are reconstructed from more than one section. 



