66 



FRANK R. LILLIE. 



lively simple matter in the case of the egg of Chcetopterus, be- 

 cause all ripe eggs reach such a stage in about twenty minutes 

 after they are put in sea water, and undergo no further progres- 

 sive development unless fertilized or otherwise suitably stimulated. 

 This stage may be described as follows (Fig. 4) : 



xf^W^^'''-- '<'' "';'.'- : -%-%K 

 X., <" :-'-:. '://, . ,\V- VN: '.-^ VT&X 



K "'"^' : -^ : fd ;* $9$I&M 1^ 



FIG. 4. Section of the egg of Chcetopterus at the stage used for the experiments. 

 See text for description. 



The substance of the polarized egg shows the following areas 

 and zones : 



1. The spindle area lies at the animal pole and includes the 

 spindle and the protoplasm in which the astral rays are developed. 

 This area is predominantly basophile, but it may include a very 

 few acidophile yolk granules. The astral rays may encroach 

 slightly on (2) and (3). 



2. The central spongy area lies near the center of the egg in 

 the direct line of prolongation of the spindle. Its spongy ap- 

 pearance is due to paucity of granules and not to actual vacuoli- 



