194 POSITION OF SMELL-ORGANS chap. 



tion of the apple several times, placing it at a sufficient distance, 

 to be sure they could not see it, but they always hit it off cor- 

 rectly, after raising their heads and moving their long tentacles 

 in every direction. It then occurred to him to hold the apple 

 in the air, some centimetres above the head of the Limax. 

 They perceived where it was, raised their heads and lengthened 

 their necks, endeavouring to find some solid body on which to 

 climb to their food. 



Several of the land Mollusca have the power of exhaling a 

 disagreeable smell, Hyaliyiia alliaria smelling strongly of garlic, 

 and Stenogyra decollata of laudanum ; but this need not be any 

 argument for the sense of smell in the creatures themselves. 

 / Position of Olfactory Organs in Pulmonata. — Most author- 



ities are of opinion that the olfactory organs are situated in the 

 tentacles. Moquin-Tandon considered that in the Helicidae and 

 ! Limacidae the sense of smell is confined to the little knob or 

 elevation at the end of the longer tentacles, close to the eye. 

 He found that when he cut off these tentacles both in Limax and 

 Arion^ the creatures were quite unable to discover the where- 

 abouts even of strongly-scented food. The same author believed 

 that in the Basommatophora the sense of smell was present in 

 the whole of the tentacle, which is covered with an exceedingly 

 sensitive ciliated epithelium. Lacaze-Duthiers, however, places 

 the olfactory sense in this group at the outer side of the base 

 of the tentacles, near to the eyes. Some authorities ^ deny that 

 the Helicidae have the olfactory organ at the tip of the tentacles, 

 and locate it in a pedal gland near the mouth, which contains 

 conspicuous sensitive cells. A Helix whose tentacles had been 

 removed manifested its repulsion to the smell of spirits of 

 turpentine, while another JTelix, which was unmutilated, did 

 \ not object to the turpentine being held between its tentacles. 

 I Altogether, then, the exact position of the smell-organ in the 

 Helicidae must be considered as not yet thoroughly determined. 

 Simroth holds that the sense of smell is distributed over the 

 whole soft integument, and is especially concentrated in the 

 feelers, and in the neighbourhood of the respiratory orifice.^ 



In nearly all marine Mollusca yet examined, the organ of 

 smell or osphradium is in situation intimately connected with 

 the breathing organs, being generally placed near their base, 

 1 E.(j. Sochaczewer, Zeits. wiss. Zool. xxxv. p. 30. - Zool. Anz. 1882, p. 472. 



