1881.] The Brain of the Locust. 295 
bees, wasps, &c., he seemed to think the intelligence of insects 
stood in direct relationship to the development of these bodies. 
The form of these structures is described by the same author as 
being, when fully developed, as in the bee, like a pair of disks 
upon each side, each disk being folded together and bent down- 
wards before and behind, its border being thickened and the inner 
portion radiated. By very careful dissection he found these bodies 
to be connected on each side with a short pedicle, which bifur- 
cates 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 (neurilem- 
m These convoluted bodies and the stalks upon which they 
are mounted are compared by Dujardin to certain kinds of mush- 
rooms, and this idea has been retained 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, is his description, notwithstanding 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 descrip- 
tion we apply the term “ mushroom body ”’ to the entire 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 
mushroom body rests on a rounded mass of granulo-fibrous 
nerve matter; this rounded mass or base of the column is called 
the ¢rabecula (P\. 11., Fig. 2, tvad.). The two trabeculz (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 contain- 
ing 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 535 of an inch. 
The substance of the trabecula is seen to be minutely fibrous 
