434 



WATASE. 



[Vol. VIII. 



by the egg of Unio (Fig. i). When the egg of Unio is killed 

 with an osmo-picric mixture, and stained with acid-fuchsin, and 

 afterward washed with the alcoholic solution of picric acid, we 

 see the centrosome standing out with a remarkable sharpness 

 from the rest of the cell-structure, inasmuch as the acid-fuchsin 

 deeply stains the centrosome, while the spindle fibres and the 

 rays of the aster remain practically unstained. On casual 

 observation, we see nothing in the cell that can be compared 

 with such a centrosome (Fig. i, C). The view that regards 

 the centrosome as a unique organ of the cell would certainly 



Fig. I. The egg of Unio complanata. C. C. centrosome; N". nucleus; Yk. 

 yolk-granules. The egg was killed in the picro-osmic mixture, and stained with 

 acid-fuchsin, and afterward washed with the alcoholic solution of picric acid. 

 The centrosome appears to be hollow, the optical section shows it as a very thick 

 ring of deeply staining substance. 



seem justified, at least, if we cannot find any element in the 

 cell that can be directly compared with it, as in the case of the 

 egg-cell of Ufiio. 



But we must remember that we may be here dealing with an 

 extreme case, and therefore, just the example to be avoided on 

 account of the excessive development of the centrosome, if we 

 wish to find any element in the cell that is to be directly 

 compared with it. 



