I WAS much interested in Mr. A. Stephen Wilson's letter upon this subject (NATURE, vol. xx. p. 55). I must, however, demur to his statement that “all insect-galls are in reality leaf-buds or fruit-buds,” as too sweeping to be accurate. I can hardly include in the above category the numerous galls which make their appearance on the growing leaves of trees, such, for example, as the oak-spangles (of Neuroterus malpighii) or the galls of the Spathegaster baccarum, Andricus curvator, c thus the development of the bud-galls of Cynips kolleri, Teras terminalis, and Aphilothrix gemma, is to be seen in the spring, summer, and early autumn, but not in winter time when the tree growth is arrested. My observations at that time led me to suppose that the currant galls of the oak and others of the same class only grow during the growth of the leaf to which they were attached.