Thus Landois denied that the antennæ had the sense of smell, and declared that the pits in the antennæ of the stag beetle were auditory organs. So, also, Paasch rejected Leydig’s conclusion, while he sought to again reinstate the old opinion of Rosenthal as to the olfactory nature of the frontal cavity of the Diptera. In spite of the exact observations and interesting anatomical discoveries of Forel in ants, made in 1874, there appeared the great work of Wolff on the olfactory organs of bees, in which this observer, with much skill and acuteness, sought to give a basis for the hypothesis of Kirby and Spence that the seat of the sense of smell lay in the soft palatine skin of the labrum within the mouth (_i.e._ the epipharynx). Joseph, two years later, drew attention to the stigmata as olfactory organs, referring to the olfactory girdle, and Forel sought by an occasional criticism of Wolff’s conclusions to prove experimentally the olfactory function of the antenna; but Graber, in his widely read book on insects, defended the Wolffian “nose” in the most determined way, and denied to the antennæ their so often indicated faculty of smell. In 1879 Berté thought he had observed in the antenna of the flea a distinct auditory organ, and Lubbock considered the organs of Forel in the antennæ of ants as a “microscopic stethoscope.” In 1879 Graber described a new otocyst-like sense-organ in the antennæ of flies, which was accompanied by a complete list of all the conceivable forms of auditory organs in arthropods. In this work Graber described in Musca and other Diptera closed otocysts with otoliths and auditory hairs, as Lespès had previously done. But Paul Mayer, in two essays, refuted this view in a criticism of the opinion of Berté, referring the “otocysts with otoliths” to the well-known antennal pits into which tracheæ might pass. Mayer did not decide on the function of the hairs which extend to the bottom of the pits; while in the most recent research, that of Hauser, the author again energetically contended for the olfactory function of the antennæ. Both through physiological experiments and detailed anatomical investigations Hauser sought to prove his hypothesis, as Pierrot, Erichson, Slater, and others had done before him, besides working from an evolutional point of view. In a purely anatomical aspect, especially prominent are his discovery of the singularly formed nerve-rods in the pits and peg-like teeth of the Hymenoptera and their development, as well as the assertion that numerous hairs in the pits described by Leydig, Meyer, etc., should be considered as direct terminations of nervous fibres passing into the pits. In the pits he farther, with Erichson, notices a serous fluid, which may serve as a medium for the perception of smells. Among the latest articles on this subject are those of Künckel and Gazagnaire, which are entirely anatomical,