No. 2.] 



HOMOLOGY OF THE CENTROSOME. 



435 



Let us begin, therefore, with the cell in which the centrosome 

 has not attained such an extraordinary development, as in the 

 case of Unio. 



Such a cell we find in the leucocyte. The accompanying 

 illustration (Fig. 2), which is taken from the beautiful work 

 of Heidenhain, represents the white blood corpuscle of the 

 Salamander. In the center of the aster we find two pieces of 

 deeply staining bodies, which are the centrosomes {C). Around 

 them, there exists a zone composed of smooth cytoplasmic fila- 

 ments radiating outwards. Along the periphery of this zone 

 we find a number of granules. These granules are considerably 

 smaller in size compared with the centrosome. The cyto- 



Fiff. 2. 



C-'-V 



M"' 



Fig. 2. The leucocyte of Sahnnander, showing the radical system of the cyto- 

 plasmic filaments, (aster) and the distribution of the microsomes {M.) ; C, centro- 

 some ; N. nucleus. After Martin Heidenhain, Ueber Kern und Protoplasvia, 

 Festschrift fiir A. von Kolliker, 1892, Taf. X, Fig. 9. 



plasmic filaments, which run from the periphery of the above- 

 mentioned zone outward, contain a series of fine granules of 

 varying sizes. These highly staining granules are the fnicro- 

 somes (Fig. 2, J/.), or more strictly, the cyto-microsomes, and 

 all of them stain exactly like the centrosome. The microsomes 

 are imbedded in the substance of the cytoplasmic thread, and 

 are different from the metaplasmic products, such as the non- 

 living granules, nutritive particles which are often quite 

 abundant in the cell. 



