No. 2.] THE OVARIAN EGG OF LIMULUS. 183 



exist, apparently independently of the granules derived from 

 migrating nucleoli. 



In the egg of Limulus I have conclusive evidence of the exist- 

 ence, both in earlier and in later stages, of a centrosome and 

 sphere in the midst of the granules of the inner zones (PI. XIV, 

 Figs. 21, 47, 48); and as will appear from the following con- 

 siderations of that body, I believe that this is the structural 

 basis around which the metaplasmic granules of the inner zone 

 collect and give rise to the conspicuous body known as the 

 vitelline-body of Balbiani. In that way I would account for 

 the appearances in the living egg represented in PI. XIII, 

 Fig. 16, a. 



The Centrosome and Sphere (Vitelline-Body). 



As soon as the growing egg can be distinguished as such, 

 there may be seen in the cytoplasm, in the immediate neigh- 

 borhood of the germinal vesicle, a body which differs from all 

 other parts of the egg in its staining reactions (PI. XIV, Figs. 

 34, 38, 40). It is brought prominently into view by means of 

 Heidenhain's iron-haematoxylin ; by the Biondi-Ehrlich mix- 

 ture ; Weigert's picro-carmine ; Delafield's haematoxylin, either 

 alone or followed with picric acid ; by means of borax-carmine 

 and picric acid ; Ehrlich's haematoxylin and acid fuchsin or 

 eosin ; by erythrosin, either alone or followed with cyanin ; 

 and finally by means of Lyon's blue and lithium-carmine or 

 safranin. 



When first observed, it has the form of a crescent closely 

 applied to the germinal vesicle. In the latter double stain it 

 may be made very conspicuous, being differentiated from all 

 other parts of the egg, both germinal vesicle and cytoplasm. 

 These stain red, while the crescent stains a bright blue. In the 

 widest portion of the crescent is a clear area containing central 

 granules (Fig. 42). 



This central area, with its granules, appears to be the essen- 

 tial part of the body, inasmuch as it is this which continues to 

 exist in various forms as the egg continues to grow. The horns 

 of the crescent seem to disappear early (Figs. 42-48). 



