Experiment 3.—Fragments of a large fly were placed close to the apex of a vigorous leaf, as well as along half one margin. [page 372] After 4 hrs. 20 m. there was decided incurvation, which increased a little during the afternoon, but was in the same state on the following morning. Near the apex both margins were inwardly curved. I have never seen a case of the apex itself being in the least curved towards the base of the leaf. After 48 hrs. (always reckoning from the time when the flies were placed on the leaf) the margin had everywhere begun to unfold. Experiment 4.—A large fragment of a fly was placed on a leaf, in a medial line, a little beneath the apex. Both lateral margins were perceptibly incurved in 3 hrs., and after 4 hrs. 20 m. to such a degree that the fragment was clasped by both margins. After 24 hrs. the two infolded edges near the apex (for the lower part of the leaf was not at all affected) were measured and found to be .11 of an inch (2.795 mm.) apart. The fly was now removed, and a stream of water poured over the leaf so as to wash the surface; and after 24 hrs. the margins were .25 of an inch (6.349 mm.) apart, so that they were largely unfolded. After an additional 24 hrs. they were completely unfolded. Another fly was now put on the same spot to see whether this leaf, on which the first fly had been left 24 hrs., would move again; after 10 hrs. there was a trace of incurvation, but this did not increase during the next 24 hrs. A bit of meat was also placed on the margin of a leaf, which four days previously had become strongly incurved over a fragment of a fly and had afterwards re-expanded; but the meat did not cause even a trace of incurvation. On the contrary, the margin became somewhat reflexed, as if injured, and so remained for the three following days, as long as it was observed. Experiment 5.—A large fragment of a fly was placed halfway between the apex and base of a leaf and halfway between the midrib and one margin. A short space of this margin, opposite the fly, showed a trace of incurvation after 3 hrs., and this became strongly pronounced in 7 hrs. After 24 hrs. the infolded edge was only .16 of an inch (4.064 mm.) from the midrib. The margin now began to unfold, though the fly was left on the leaf; so that by the next morning (i.e. 48 hrs. from the time when the fly was first put on) the infolded edge had almost completely recovered its original position, being now .3 of an inch (7.62 mm.), instead of .16 of an inch, from the midrib. A trace of flexure was, however, still visible.