2o6 BYRNES. [Vol. XVI. 



been able to determine ; they vary in size, number, and position, 

 as do also the deeply staining bodies which probably correspond 

 to the yolk-nuclei of other forms. As the ovarian eggs enlarge 

 and leave the walls of the follicles, these structures disappear 

 and the cytoplasm becomes more uniform in appearance. 



3. First Maturation Spindle. Extrusion of the First 

 Polar Body. 



As long as the archiamphiaster remains at the equator of 

 the egg, the two polar asters are of the same size and retain the 

 appearance already described. Within half an hour after the 

 eggs have been deposited the archiamphiaster, or the first 

 maturation spindle, as it will be called henceforth, assumes a 

 radial position at the upper pole of the Q.g^. The arrangement 

 of the centrosphere in concentric rings often persists until after 

 the extrusion of the first polar body, as shown in PI. XI, Figs. 

 9 and 10. Sometimes, however, before the first polar body is 

 extruded, the centrosphere assumes a very different appearance. 

 The two distinct zones that are so characteristic of the stage 

 of the archiamphiaster gradually fade away, and the center of 

 the aster now appears as a deeply stained, homogeneous body, 

 surrounded by a less deeply staining zone from which the 

 astral rays diverge (PL XI, Figs. 7 and 8). 



The astral rays in the eggs of Limax are formed by filaments 

 which can be traced far out into the cytoplasm in almost straight 

 lines (PI. XI, Figs. 3, 7, and 8). During the stage of the first 

 maturation spindle, Mark has found that the rays of the periph- 

 eral aster are slightly bent so as to form a spiral. I have 

 never seen spiral asters in connection with the first maturation 

 spindle in Limax agrestis. 



The different forms under which the centrosphere of the 

 first maturation spindle appears (PI. XI, Figs. 7-9) may be 

 due to different lengths of time elapsing between the forma- 

 tion of the archiamphiaster and the extrusion of the first polar 

 globule. The formation of the first polar body is preceded 

 by a slight flattening of the upper pole of the ^^g. As the 

 distal aster approaches the periphery of the &gg, the rays are 



