DIFFERENT FORMS OF OLFACTORY ORGANS 279 



teeth. We may add that supposed organs of smell occur on the 

 antennae of Campodea (Fig. 282). 



Kraepelin also thus briefly summarizes Hauser's statements as to 

 the forms of the different organs of smell. 



The manifold nature of the antennal organs has, by Hauser, from thorough 

 studies of the nerve-elements belonging to them, been not simplified but ren- 

 deml more complicated. According to this naturalist we may distinguish the 

 following forms which the olfactory organs may assume : 1. " Pale, tooth-like 

 chitinous hairs on the outer surface of the antennae, which are perforated at the 

 end ; nothing is known as to the relation of the nerve passing into it (Chrysopa, 

 Anophthalmus). 2. In pit-like depressions of the antennae arise nerve-rods 

 (without a chitinous case) which stand in direct relation with a ganglion-cell 

 lying under it. These pits are either simple, viz. with only an ' olfactory rod ' 

 (Tabanus, Fig. 283, and other Diptera, Vanessa), or compound (Muscidte, and 

 most other Diptera, and Philonthus). It is important that these pits are partly 

 open (in the above-named groups of insects), and partly closed and covered with a 

 thin membrane, under whose concavity the olfactory rods end (Orthoptera, 

 Mflolontlia, and other lamellicorns). 3. Short, thick pits sunken slightly into the 

 surface of the antennae, and over this a chitinous peg perforated at the end, in 

 whose base, from the interior, projects a very singular nerve-peg, which is situated 

 over an olfactory ganglion-cell, and provided with a slender crown of little rods, 

 and flanked on each side by a flagellum-cell (Hymenoptera). 4. Round or crevice- 

 like pits covered over by a perforated chitinous membrane with nerve-rods like 

 those in 3, but in place of the flagellum-cell with 'membrane-forming' cells 

 spread before it. Hauser finally mentions further differences in the ganglion-cells 

 sent out into the nerve-end apparatus. These exhibit in Diptera and Melolontha 

 only one nucleus, in Hymenoptera a single very large one (with many nucleoli) 

 and three small ones, in Vanessa six, in Orthoptera a very large number of 

 nuclei, etc." 



LITERATURE OF THE ORGANS OF SMELL 



Reaumur, Rene Ant. de. Me"moires pour servir a 1'histoire des insectes. Paris, 



1734-42. (i, 283 ; ii, 224). 

 Lesser, F. C. Insecto-theologia, 1740, p. 262. 

 Roesel, A. J. Insektenbemstigungen, 1746, ii, p. 51. 

 Reimarus, H. S. Allgemeine Betrachtung ueber die Triebe cler Thiere haupts- 



achlich ihre Kunsttriebe (Instinct). Hamburg, 1760, p. 355. 

 Sulzer, J. H. Die Kenntzeichen der Insecten. Zurich, 1701. 

 Lyonet, P. Traite anatomique de la chenille, 1762, pp. 42, 96, 195. 

 Comparetti, A. De aure iuterna comparata. Patavii, 1769. 

 Bonnet, C. (Kuvres completes, 1779-1783, ii, p. 36. 



Contemplation de la nature, f'h. iii, p. 18. 



Scarpa, Ant. Anatomicae disquisitiones de auditu et olfactu. Ticini, 1789. 

 Huber, F. Nouvelles observations sur les abeilles, 17! 12, ii, p. 475. 

 Lehrmann, M. C. G. De antennis insectorum. Londini, Hamburg!, 1799, p. 48, 



Diss. posterior ; Hamburg and London, 1800, p. 80 (especial sense, aerocepsis). 

 Latreille, P. A. Ilistoire naturelle des crustace's et des insectes, 1806-1809, 



ii, 50. 



Blainville. M. H. D. Principes d'anatomie compared, 1822, i, p. 339. 

 Duges, A. L. Traite" de physiologic comparee, 1838, i, p. 161. 



