The first to study the morphology of the ovipositor was Lacaze-Duthiers, who referred their origin to the partially atrophied dorsal or ventral sclerites of one of the last abdominal segments; a view accepted by Gerstaecker[37] (Figs. 186, 187). The present writer (1866), however, showed that the sting of Bombus was not formed of the reduced pieces of the segments themselves, but arose from special outgrowths on the ventral side of the eighth and ninth abdominal segments. These appendages he did not at first regard as the homologues of the limbs, until in 1871, after studying the origin of the spring of the Podurans (Isotoma), he found that it was a true jointed appendage and therefore a homologue of a pair of the styles forming the ovipositor of the winged insects, and that the three pairs of styles of the latter were homologues of the thoracic legs and cephalic appendages. The view was stated in the Guide to the Study of Insects. (See also Amer. Nat., March, 1871, p. 6.) Kraepelin also affirms that the styles of the ovipositor are segmental appendages and homologues of the antennæ, wings (_sic_), and legs. [Illustration: FIG. 187.—1, abdomen of Cynips, showing the great dorsal segment, the peduncle, and the position of the ovipositor within; 2, the entire ovipositor; _a_, lateral scale; _a′_, its valve; _b_, anal scale; _b′_, stylet; _c_, support of the stylet; _e_, base or support of sting (_fi_); 3, profile showing the relation of the genital armature to the rest of the abdomen, the 6th sternite having been drawn to show its full size; 4, anal scale (_b_) and stylet; _e_, _i_, supports and body of the stylet; _c_, piece uniting the two scales; 5, lateral scale (_a_), and _a_′ sheath; _d_, support of the sting (_f_); 6, transverse section of the body through the sting (diagrammatic); _R_, internal armature; _o_, oviduct; _a_, lateral scale; _a′_ its valve; _e_, support of the stylets (_i_); _b_, anal scale; _c_, piece uniting two scales; _f_, sting; _d_, its support; 7, a second section simpler and more theoretical than the first; 8, diagrammatic, all the elements of the sting have been reduced to pieces of the same form.—After Lacaze-Duthiers. ]