348 JOURNAL OF COMPARATIVE NEUROLOGY. 
seem to be supplied somewhat differently. Those entering the 
lower are seen to originate from cells above the antennal lobes 
and upon reaching the lower lateral edges to take a transverse 
course below the body and send several branches upwards that 
subdivide arborescently producing a compact mass of branch- 
lets that recall the arborescent and bushy terminations of the 
association of fibers in the roots of the mushroom bodies. As. 
in the case of these latter fibers, it is to the compact branching 
mass of fibrils that is due the depth of color so noticeable in 
preparations stained with osmic acid or haematoxylin. Other 
fibers pass out or enter from the fibrillar substance of the brain 
immediately in front, while branches from association fibers in 
the anterior region seem to enter the anterior end and the 
posterior lower end of this portion of the body.” Samassa 
(91) states that he has not been able to detect any fibers enter- 
ing the central body. 
Histologically considered, the central body of the crayfish 
is composed of a mass of fibrils and fibers free from any admix- 
ture of nucleated cells. In the immediate neighborhood, how- 
ever, there are numerous neuroglia cells. The fibers compos- 
ing this body seem to fall into two classes: Ist, numerous fibers 
forming.a loose net-like meshwork which is continuous on all 
sides with the meshwork of fibers which seems to form the his- 
tological skeleton of the brain; 2nd, fibers which differentiate 
arborescently into numerous fine fibrils. The fibers of the sec- 
ond type are derived in part from the commissures which pass 
above (dorsad) and below (ventral of ) the central body, in part 
from fibers that originate in the dorsal nidus and in part from 
cells lying in the immediate neighborhood of the central body. 
As to the first two’ sources of these fibrils my sections give 
abundant evidence; but the last statement is based upon the 
study of one slide. In one section I discovered a cell which 
gave rise to a fiber which forked, one branch passing into the 
central body and one passing towards the adjacent commissure 
(fig. 36). 
Of the fibers which VIALLANEs claims pass from this body 
to all parts of the brain I find no trace. 
