28 JOURNAL OF COMPARATIVE NEUROLOGY. 
III. THE MORPHOLOGY OF THE CENTROSOME. 
As is shown in the illustrations, the centrosome as well as 
the sphere’ in PuRKINJE cells and in the pyramidal cortical cells, 
lie, as a rule, at the base of a main dendrite near the nucleus 
(Figs. 2, 3, and 5-10). On the other hand, the centrosome and 
the sphere in the spinal ganglion cells lie, as a rule, on the 
side of the nucleus towards the axone hillock (Figs. I, I1). 
The centrosphere is somewhat circular in cross section 
with a less quantity of protoplasm. This gives the clear and 
transparent appearance to the centrosphere. A coarse granular 
layer of the protoplasm surrounds the centrosphere, which 
layer voN LENHOSSEK termed the ‘‘plasmosphere.”’ The stain- 
able bodies (Nissi’s granules) are present in the plasmosphere, 
as in the remaining part of the cell-body, but not in in the cen- 
trosphere. These differences in the structure of the cytoplasm 
make it possible to distinguish the centrosphere from the re- 
maining structures. The appearance of a radial arrangement 
of the microsomes originates from the centrosome which lies 
within the centrosphere (Figs. 3, 7, 8, 9, 10). These radial 
lines extend from the center into the plasmosphere. The lines 
are composed of a continuous series of minute protoplasmic 
corpuscles, smaller than the centrosome, which are known as 
microsomes (HANSTEIN, 1880). These radial lines formed by 
the microsomes are covered over very often, in the case of an 
adult animal, by the great number of the stainable masses 
which almost entirely obscure the radiations, We distinguish 
the microsomes from the stainable masses by the fact that the 
1 Different authors use different terms to designate the structure of the cen- 
trosome but the present writer employs the terms which were used by Von 
LENHOSSEK—centrosome, centrosphere and plasmosphere. The ‘‘centrosome”’ 
isa group of minute corpuscles which lie centrally in the centrosphere, or 
‘‘centralscheibe.”? The ‘‘centrosphere”’ is the clear transparent area surround- 
ing the centrosome. The ‘‘plasmosphere”’ is the area with coarse protoplasmic 
granules which surrounds the centrosphere. The plasmosphere grades into the 
surrounding portion of cell body and is not clearly separated fromit. The 
present writer uses the term ‘‘sphere”’ to designate the entire structure, includ- 
ing centrosphere, radial arrangement of protoplasm and plasmosphere. 
