260 



WILLIAM B. KIRKHAM. 



therefore retained the second polar spindle some being accom-. 

 panied by the first polar body, more without it and those which 

 had been fertilized. The latter included stages from the entrance 

 of the spermatozoon through the cleavage stages. 



FIG. i. Ovarian egg showing first polar spindle. Zona pellucida represented by 

 double line. X 1200. 



First Polar Spindle (Fig. i). - - The preparations in which there 

 are stages immediately preceding the formation of the first polar 

 spindle have not been fully studied, but there is evidence of a 

 precocious division, the number of chromatin masses being be- 

 tween twelve and twenty-four. 



The first polar spindle when first formed lies with its axis per- 

 pendicular to the radius of the egg, as found by Rubaschkin 

 ('05) in the egg of the guinea-pig, and later one pole swings some- 

 what toward the center of the egg. The chromosomes of the 

 first polar spindle are short and thick (Fig 2), and vary greatly 

 in size. The spindle fibers come to more or less of a focus, 

 and centrioles have often been seen at the poles of this spindle, 

 where they are made up of several distinct, eccentrically placed 

 granules. 



