re os oe 
Turner, Mushroom Bodies of the Crayfish. 323 
INTRODUCTION. 
Mushroom-bodies, fungiform bodies, pedunculated bodies, 
are synonyms that have been applied to certain peculiar struc- 
tures found in the brains of insects. These bodies were first dis- 
covered by DujarDIN (’50). Although rediscovered by Lrypie 
(64) and Rasr-RickuHarp ('75), yet aided by osmic acid, the 
microtome and staining fluids, Dirt (’76) was the first to give 
a complete description of the whole organ. 
Thanks to the researches of more recent investigators, it 
is now well known that the mushroom-bodies occur in all classes 
of insects and that they reach their highest development in the 
Hymenoptera. Deri ('76), Brercer (’78), and VIALLANES 
(93) have found in the Decapod brain structures which they 
consider homologues of the mushroom-bodies of the Hexrapod 
brain. Kenyon (’96), as the following quotation shows, thinks 
all of these men are mistaken. ‘‘Special swellings found on 
the brains of certain of the Crustacea have been compared with 
them [the mushroom bodies], but it isto be seriously doubted, I 
think, whether such swellings or cellular heaps are properly to 
be homologized directly with them. In neither Rerzius’ figure of 
the brain of Astacus fluviatiis, nor in BETHE’s figures of the brain 
of Carcinus menas, can I find cells having the relations and the 
appearance of those I find in the bee. I have noticed nothing 
resembling the structures in isopods and amphipods, nor have 
I found indications of them in the brains of Pauropus, Poly- 
azenus, juloid diplopods, Scolopendrella, Lithobius, nor even in 
several forms of Z7hysanura that I have examined. If cells 
homologous with those filling the cup-like calyx of the mush- 
room bodies of the bee are at all present in these forms, they 
are so undifferentiated as to be indistinguishable from the gen- 
eral mass of cells about them.” 
/ The purpose of this paper is to throw additional light 
upon this problem. 
A portion of this work was done, during the summer of 
1898, in the Hull Zoological Laboratory of the University of 
Chicago. I take this opportunity to express my indebtedness 
