No. 2.] THE OVARIAN EGG OF LIMULUS. 163 



10. Other similar bodies may form within, and these likewise 

 are extruded. 



1 1 . These extruded bodies are the so-called " Nebennu- 

 cleoli." 



12. In carmine and Delafield's haematoxylin they stain 

 feebly. 



13. In the living egg they appear as shining vesicles, 

 composed of a delicate membrane enclosing a fluid in which 

 granules are suspended. 



14. They have the appearance of yolk spheres ; but as they 

 arise at a time long before the yolk spheres are formed in the 

 cytoplasm, they are not yolk spheres. 



1 5. Similar bodies are seen in the cytoplasm at this stage, 

 but they are not permanent. 



16. The part remaining after this extrusion retains its power 

 of staining in carmine stains, and may be designated the 

 nucleolus. 



17. This often has the form of a crescent. 



18. The interior of this, in rare cases, contains no stainable 

 substance, and appears as if it might be a fluid vacuole. 



19. More frequently the interior is occupied by a linin 

 network like that of the germinal vesicle, and, like it, having 

 stainable granules imbedded in it or attached to it. 



20. The crescent-shaped or circular nucleolus appears to lose 

 substance from within, and to receive substance from without. 



21. It may thus become a large hollow shell of stainable 

 substance enclosing a reticulum. 



22. The entire nucleolus may often appear as a spherical 

 mass of granules enclosed by a homogeneous membrane. 



23. These granules may sometimes be scattered, and lie 

 imbedded in a homogeneous mass resembling the outer mem- 

 brane. The granules, when they become refractive and lose 

 their power of staining, may be mistaken for vacuoles. These, 

 however, can be stained intensely in Heidenhain's iron-haema- 

 toxylin, so that a dark body appears to lie in an unstained 

 vacuole. 



24. When only one of these granules exists, it may occupy 

 the center of the nucleolus. 



