TuRNER, Wushroom Bodtes of the Crayfish. 347 
in front of (dorso-cephalad of) the optico-olfactory commissure. 
For a thorough understanding of the structure of this lobe a 
careful study of the series of sections shown in fig. 33 will be 
more instructive than any combinaiton of words could possibly be. 
Central Body. This peculiar structure seems to be found 
in the brains of all Arthropoda. Lrypre discovered it in ants 
but mistook it for a part of the commissural system. To, DIETL 
(76) belongs the credit of recognizing it as a distinct structure. 
He called it the fan-shaped body (fecherformig Gebilde). 
Later FLOGEL called it the central body by which name the 
structure is now generally known. 
VILLANES (’93) after having studied this structure in vari- 
ous insects, recognized it in the Crustacean brain; but other 
observers think that he is mistaken. Yune (’78) after a careful 
review of the work done upon the Crustacean brain, declares 
that there is no such structure ; but that there are three sets of 
transverse fibers which various men have taken for a central 
body. Kriecer (’88) in his study of the crayfish brain must 
have overlooked this body, for I find no mention of it in his 
work. JULES RICHARD (91) ‘in his work on the nervous system 
of the Copepoda does not mention < central body; but SAMASSA 
(91) in his studies of the Cladocera has found it in Szda, Daph- 
na, Bythrotrephes and Leptodora. 
In this study of the Crustacean brain I have been able to 
demonstrate the existence of a central body, not only in the 
crayfish (figs. 1, 8, 9, 17), but also in a form as low in the scale 
as Branchipus (fig. 34). 
The structure of this body has puzzled more than one in- 
vestigator. VIALLANES (’9I) asserts that it is connected by 
fibers to all parts of the brain. BERGER (78) says that the 
body receives a bundle of fibers from each side, which fibers, 
on entering the body, break up into fine fibrils). KENyoN (’96) 
thinks VIALLANES’ statement is too sweeping. He says the 
body is composed of fine fibrils many of which are derived from 
the branches of the commissure that passes by it. KENYON 
writes as follows: ‘‘Taken as a whole the fibers seem to reach 
it [central body] from nearly all directions but the two parts 
