“The fibres entering the cups from the antennal lobe, the optic ganglia, and the ventral region, spread out and branch among the arborescent endings of the mushroom-body cells. The fibres branching among the parallel fibres of the roots and the stalk lead off to lower parts of the brain, connecting with efferent or motor-fibres, or with secondary association fibres, that in their turn make such connections. This portion of the circuit has not been perfectly made out, though there seems to be sufficient data to warrant the assumption just made. [Illustration: FIG. 252.—Section 17, showing the central body (_centr. b_) and mushroom body, optic and antennal lobes (_a. l_), and procerebral lobes (_pc. l_); _o. cal_, outer division of the calyx; _op. n_, optic nerve; _trab_, trabeculum; _tc. n_, transverse nerve. ] “Such fibres existing as described, there is then a complete circuit for sensory stimuli from the various parts of the body to the cells of the mushroom bodies. The dendritic or arborescent branches of these cells take them up and pass them on out along the parallel fibres or neurites in the roots of the mushroom bodies as motor or other efferent impulses. “This, however, is not all. For there are numerous fibres evident in my preparations, the full courses of which I have not been thus far able to determine, but which are so situated as to warrant the inference that they may act as association fibres between the afferent fibres from the antennæ, optic ganglia, and ventral system, and the efferent fibres. 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 fibres of the mushroom bodies; or, in other words, a possibility of what may be compared to reflex action in higher animals.” [Illustration: FIG. 253.—Enlarged view of the trabeculum (the dotted lines _tcn_ and _obt. n_ pass through it) and its nerves, of the mushroom body,—its calices and stalk, and the origin of the optic nerve × 225 diameters: _atn_, ascending trabecular nerve; _obt. n_, oblique trabecular nerve; _tcn_, transverse nerve; _lat. n_, lateral nerve; _cent. n_, central nerve. ] The mushroom bodies have not yet been found to be present in the Synaptera, but occur in the larvæ, at least of those of most metamorphic insects (Lepidoptera and Hymenoptera), though not yet found in the larvæ of Diptera. The writer has found these bodies in the nymphs of the locust (_Melanoplus spretus_), but not in the embryo just before hatching. They occur in the third larval or nymph stage of this insect. It is evident that by the end of the first larval stage the brain attains the development seen in the third larval state of the two-banded species (_C. bivittatus_). [Illustration: