iNo. 2.] THE OVARIAN EGG OF LIMULUS. 197 



only possesses the typical form of a centrosphere, the many 

 forms of the real aster found in the dividing cells, in leucocytes, 

 and in the fertilized egg of Ascaris megalocephala, but also the 

 less typical forms observed in sperm cells as " Nebenkern," 

 and in the resting ganglion cells. 



The vitelline-body in the ovarian egg of Lhnidus is genet- 

 ically the centrosotne and sphere of the dividing oogonia, and con- 

 tinues to be the centrosotne and attraction sphere of the growifig 

 ovarian egg. 



That this centrosome and sphere may assume the form of 

 the vitelline-body as originally described, seems evident from 

 a comparison of Figs. 60-64, 70-72, 95 with the figures of 

 Balbiani (64), ('79), ('82), ('83), ('93) ; of v. Wittich ('49) ; Carus 

 ('50) ; Schiitz ('82) ; and Henking ('87) ; and becomes very evi- 

 dent when preparations of the ovary of Limulus and of the 

 spider are directly compared. 



The most important recent papers on the vitelline-body, 

 Julin ('93), Mertens ('93), Balbiani ('93), and Henneguy ('93), 

 also suggest strongly a probable relation of this body in other 

 eggs to the centrosome and sphere. 



Position of the sphere. ■ — In the youngest eggs the sphere 

 is always situated close to the germinal vesicle, as described 

 above. It may remain in this position or it may become 

 removed from the germinal vesicle so as to occupy a posi- 

 tion midway between it and the periphery of the egg (PL XIV, 

 Figs. 49, 56). At times it may even occupy a more excentric 

 position (Fig. 70). 



There appear to be three causes that can be assigned for 

 this difference in position. First, a difference in the tension 

 or contraction of the radial fibers ; second, a difference in 

 the local accumulation of the amorphous substances in the 

 interfilar spaces ; third, differences in actual growth of the 

 cytoplasmic body. 



1 he position of the metaplasm varies with reference to the 

 central structure. It may spread out on either side of it, 

 causing a density of the radial fibers lying close to the germi- 

 nal vesicle, and thus causing the horns of the crescent (PI. XIV, 

 Fig. 47). From this position it may collect around the central 



