With Figure 6, we leave the ventral lobe of the ganglion and come to the lower portions of the dorsal lobule. The important filaments crossing this section from the front to the back are called lower dorsal connective filaments. We notice as they proceed some small masses of dotted substance, and, in addition to these, dark colored dots which are the result of the knife having cut crosswise through several fascicles of ascending fibres. We shall find out by means of the sections taken from different parts and placed so as to allow of our better observation, what these ascending fibres are. The crural lobule, always exhibits the same characteristics. We have given it a homogeneous aspect in our drawing. As a fact it presents in its sections a vast number of structural details. But these details being very difficult to understand, we prefer not to dwell upon them. Section 7 passes through the very midst of the lower dorsal connective filaments; these filaments being in two pairs, one external and the other internal. The external pair, situated somewhat lower, has here disappeared, and the inner pair is the only one to be seen. Some transversal fibres, whose direction appears to me difficult to follow, divide the inside dorsal connective filaments at two different points, and assume the figure of a square; this square has two black dots, produced by the section of the ascending fibres. A little higher, in Figure 8, the lower connective filaments have disappeared and the fibrillar substance of the ganglion is furrowed by long transversal fibres, of which a part seems to serve the function of joining the two crural lobules, whilst the remainder, proceeding towards the black dots before mentioned, continue their progress with the fasciculi of ascending fibres. These are no other than ascending fibres which, having changed their direction at the plane of the section, proceed almost in a horizontal plane. In Section 9 we follow the course of the medial dorsal connective filaments, separated from the lower connective filaments by the fibres having a transverse direction, seen in Figure 8. The medial dorsal connective filaments are four in number, an outer pair and an inner pair. At the moment when they leave the prothoracic ganglion, they cross a region where the fibrillar substance is both thicker and darker. In Figure 10 the medial connective filaments are on the point of disappearing; they receive certain fibres coming from the crural lobules, which are now reduced in dimensions. Section 11 shows us the lower dorsal connective filaments, which are the slenderest of all and of which there are but one pair; the crural lobule now disappears. In the middle of the figure, we observe a small collection of conjunctival cells which, as we have supposed, indicates the point where in the course of development the two symmetrical portions of the ganglion have not been perfectly fused together. Finally Section 12 shows two lateral masses of