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MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



mushroom bodies, form a characteristic portion of the brain of adult insects. They have not yet 

 been found to be present in the Synaptera, but occur in the ]arva^ at least of those of most meta- 

 morphic insects (Lepidoptera and Hymenoptera), though not yet found in the larva" of Diptera. 



Fig "VT —Section through the brain of Caloptcnus 

 bivittatus in the thirtl lirvil st igc '^howm^ tlio two 

 heniisphcr4 s or sifles of the br an mdtheotelU and 

 o( cllir nerves whi< h are seen to ii ise from the top 

 of the hemispherea directly over the caliccs ; o. cal.^ 

 outer calyx of left mnshroom body. The lighter 

 portions represent the gninulo-fibrous central part of 

 the brain, and the dark the cortical ganglionic cells. 



Fiu. VII.— Section thrnugh tlie brain of aiilnlt Caloptenus spretus, passing 

 through the mashroom bodies ; o. cal., outer calyx ; centr. b., central body ; 

 ant. I., antenn® lobe; op, n., optic uerve; cs, com. I., cerebral lobe. 



I have found these bodies in the nymphs of the locust {Caloptemis spretus)^ but not in tlie embryo 

 just before hatching. They occur in the third larval or nymph stage of this insect, and in my 

 essay I stated : " It is evident that by the end of the first larval stage the brain attains the develoi^- 

 ment seen in the third larval state of the two-banded species" (0. hivittatus). 



Fig. VIII.— Enlarged view of the trabecula and its nerves, of the mushroom body, its caliccs and double stalk (caulicvlu.s otid pedicel), and 



the origin of the oj)tic nerve. 



The result of my studies on the brain of the embryo locust was that fntm the ^'embryonic 

 cerebral lobes are eventually developed the central body and the two mushroom bodies" (p. 237). 

 Fig VI, copied from my essay (PL xii, Fig. 1), shows the eai'Iy condition of the mushroom bodies 



