486 ROBERT CHAMBERS, JR. 



ing the central clear zone (heller Hof of Boveri) surrounding 

 the centrosome and the adjacent zone which contains no alveolar 

 spheres but in which radii are closely crowded together. In the 

 living object no trace of radiation appears in any zone of the 

 hyaloplasm-sphere and Wilson himself raised the question 

 whether the rays seen in its outer zone in sections may not be 

 coagulation products. Neither is any structure resembling a 

 central body or centrosome visible. 



Eggs which have been kept flattened for some time in a shallow 

 hanging drop tend to undergo pathological changes. The 

 hyaloplasm-sphere is quickly affected by the abnormal con- 

 ditions so that frequently cytoplasmic granules (usually the 

 microsomes only) enter the sphere and arrange themselves in 

 more or less regular and concentric rings. Sharply defined 

 radiating lines appear only in coagulated eggs. In some the 

 lines start from the very center of the sphere, in others they 

 not reach the center leaving a central clear area which do 

 develops a finely granular or aveolar structure. Thus several 

 of the types of centrosomal structures figured by Wilson in his 

 book on the cell ('00, p. 310) can be simulated in the Echinarach- 

 nius eggs by subjecting them to abnormal conditions. 



In the living egg the microdissection method discloses a decided 

 difference in consistency between the substance of the hyalo- 

 plasm-sphere and the hyaloplasm surrounding the sphere. I 

 shall substitute in this paper the term 'sphere' for the hyalo- 

 plasm-sphere and refer to the contents of the sphere as the sphere 

 substance or sphere liquid. 



Jj.. Protoplasm 



When protoplasm is examined with transmitted light it appears 

 as a hyaline perfectly homogeneous substance in which granules 

 may or may not be embedded. In ova the granules are fairly 

 uniform in size and usually so crowded together as to give to the 

 cytoplasm of the egg the appearance of an alveolar structure. 

 That the visible granules are not a constant feature of proto- 

 plasm may be seen in early germ cells (Chambers, '15) where 

 the protoplasm is optically homogeneous. Very young ova also 



