POLARITY AND BILATERALITY OF THE ANNELID EGG. 



under the influence of centrifugal force, this aggregation, which 

 does not exist in the control eggs, must have come from the distal 

 hemisphere. But as they lie at the central end of the spongy 

 area, and are most numerous opposite the center of this area, and 

 diminish towards the sides, it is obvious that they must have 

 come from the interior of this area. 



They are in fact a swarm of microsomes moving under the in- 

 fluence of centrifugal force, but delayed on the borderland of the 



Jib 



b.C 



FIG. 7. Section of an egg of Chcztopterus centrifuged 1,150 revolutions in 31 sec- 

 onds at a radius of 13 cm. The primary axis of the egg is unknown in this case. 

 2-2, secondary axis ; j, ectoplasmic zone ; b.c., basophile cap ; g.c., gray cap ; h.b., 

 hyaline band ; s.a., spongy area; stained in iron hEematoxylin and orange G. 



hyaline band (cf. Fig. 7), where they belong by virtue of their 

 specific gravity, by the greater density (or other mode of resist- 

 ance) of the wall of the spongy area. 



This property of the wall of the spongy area also explains the 



