VIEWS AS TO THE ORGANS OF SMELL 267 



sense of smell is localized in the antennae (teeth and pits), and here the work of 

 Hensen might be mentioned, which in 1800 had a decided influence upon the 

 conclusion of some inquiries. 



Thus Landois denied that the antennae had the sense of smell, and declared 

 that the pits in the antennae 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 dis- 

 coveries of Forel in ants, made in 1874, there appeared the great work of Wolff 

 on tire 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 in- 

 sects, defended the Wolffian "nose" in the most determined way, and denied 

 to the antennae their so often indicated faculty of smell. In 1879 Berte" thought 

 he had observed in the antenna of the flea a distinct auditory organ, and Lub- 

 bock considered the organs of Forel in the antennae of ants as a "microscopic 

 stethoscope." In 1879 Graber described a new otocyst-like sense-organ in the 

 antennas 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 Lairs, as 

 Lespes had previously done. But Paul Mayer, in two essays, refuted this view 

 in a criticism of the opinion of Berte", referring the "otocysts with otoliths" to 

 the well-known antennal pits into which trachefe 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 antenna?. Both through physio- 

 logical experiments and detailed anatomical investigations Hauser sought to 

 prove his hypothesis, as Pierret, 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 Kiinckel and Gazagnaire, which are entirely 

 anatomical, while the latest treatise of Graber on the organs of hearing in insects 

 opposes Hicks's theory of the olfactory function of the nerve-end apparatus in 

 the halteres, wings, etc., and argues for the auditory nature of these structures. 

 Finally, according to Voges, the sense of smell is not localized, but spread over 

 the whole body. 



My own observations on different groups of insects agree, in general, with 

 those of Ferris, Forel, and Hauser, without being in a position to confirm or 

 deny the varying relations of the Hemiptera. That irritating odorous substances 

 (chloroform, acetic acid) cause the limbs to move in sympathy with the stimu- 

 lus, I have seen several times in Acanthosoma ; still it may be a gustatory rather 

 than olfactory stimulus. 



Turning now from speculation and simple observation to exact anatomical and 

 histological data, the nerve-end apparatus seems to have a distinct reference to 



