1896.] “ Mushroom Bodies” of the Hexapod Brain. 649 
situated as to warrant the inference that they may act as asso- 
ciation fibers between the afferent fibers from the antenne, 
optic ganglia, and ventral system and the afferent fibers. There 
is then a possibility of a stimulus entering the brain and passing 
out as a motor impulse without going into the circuit of the 
fibers of the mushroom bodies, or, in other words, a possibility 
of what may be compared to reflex action in higher animals. 
It appears then that the supposition of Dujardin is well sup- 
ported by the finer structure of the hexapod brain. , For it is 
evident from the details known since the publication of Flogel’s 
paper, that the cells composing the mushroom bodies have 
been very highly differentiated in some of the hexapods, and 
this in just those forms living the most complex lives. No 
such bodies are to be found in the lower forms. I have never 
seen them, nor any indication of them, in the Thysanura, 
Chilopoda? Scolopendrella, the Pauropoda and other Myria- 
poda, nor in any of the Crustacea that I have thus far exam- 
ined. Without doubt an application of the Golgi or methylen 
blue methods would reveal elements in some these forms that 
might be compared with the cells of the mushroom bodies; 
but they would probably be found not so completely different- 
iated from other fibers as they are in the honey bee and other 
Hymenoptera. It may be mentioned that one does not recog- 
nize such cells in the cray-fish and the crab as figured by 
Retzius and Bethe. And it scarcely need be said that no such 
elements are shown in Retzius’ figure of the brain of Nereis. 
BIBLIOGRAPHY. 
Bellonci, ’82. Intorno alla struttura e alle connessioni dei 
lobi olfattori negli artropodi superiori e nei vertebrati. Reale 
Acead. d. Lincei. (From Cuccati.) 
Berger, ’78. Untersuchungen über den Bau des Gehirns 
und der Retina der Arthropoden. Arb. d. Zool. Inst. Wien u. 
Triest., I, 173-220. 
?St.-Remy (’90) describes mushroom bodies as occuring in Scutigera, which if 
rdance wi 
homologous with the mushroom bodies of Hexapoda, is in acco 
Dujardin view 
