232 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
each disk being folded together and bent downwards before and behind, its border 
being thickened and the inner portion radiated. By very careful dissection he found 
these bodies to bo connected on each side with a short pedicle, which bifurcates below 
to end in two tubercles. One of these tubercles is directed towards the middle line, 
and approaches but does not touch the corresponding process of the opposite side. 
The second tubercle is directed forwards, and is in close relation to the front wall of 
the head, being only covered by the pia mater [neurilemma]. These convoluted 
bodies and the stalks upon which they are mounted are compared by Dajardin to cer- 
tain kinds of mushrooms, and this idea has been ictained by more recent writers on 
the subject. 
The form of the mushroom body is much more complicated in the 
bee or ant than in insects of other orders. In the cockroach and in other 
Orthoptera, notably the locust, the four divisions of the calices are united 
into two; while the structure of the calyx in the cockroach is quite 
different from that of the locust. Mr. Newton, in his description, not- 
withstanding Dujardin's statement, appears to practically limit the term 
" mushroom body" to the cap or calyx on the end of the stalk. In the 
following description we apply the term " mushroom body " to the en- 
tire structure, including the base or trabecula, the double stalk, and the 
cap or calyx. 
So far as we have been able to observe, the double stalk of the mush- 
room body rests on a rounded mass of granulo -fibrous nerve matter; this 
rounded mass or base of the column is called the trabecula (PI. X, Fig. 
2, trab.). The two trabecular (one in each hemisphere) are much more 
widely separated (in my sections) than in the cockroach or in those 
insects studied by Flogel ; the space between them being filled by a 
loose cellular mass containing small nucleated cells. The thickness of 
each trabecula is greater than that of the double stalk. Section 14 
passes through the outer or anterior edge of the trabecula, and also 
through the calices at some distance from the edge. Section 18 (Fig. 4) 
does not include it, though showing well the mushroom body, with the 
exception of the base of the double stalk. It follows that the thickness 
of the trabecula is about 3^ of an inch. 
The substance of the trabecula is seen to be minutely fibrous under a 
power of 725 diameters, with masses of granules among the fibers which 
are much finer than in the optic or antennal lobes. At the point passed 
through by section 17 the trabecular appear to have no connection with 
the stalk, but the latter appear to stop abruptly just before reaching it. 
the envelope of ganglionic cells and fibers surrounding the trabecule 
being interposed between the base of the stalk and the trabecula. (This 
does not preclude the fact that the stalk does not arise from the trabe- 
cula, though there are no signs of it in this section ; for it clearly ap- 
pears to thus arise in the drawings and descriptions of Dietl, Flogel, 
and Newton;. 
The structure of the trabecular in the locust, judging from our sections, 
appears to be more complex than would be inferred from the observa- 
tions of the other observers just mentioned. Section 17 (PI. X, Fig. 2, 
trab.) passes through the middle of each of these bodies, and it then ap- 
