194 POSITION OF SMELL-ORGANS chap. 



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' correctly, 

 after raising their heads and moving their long tentacles in every 

 direction. It then occm-red 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, Hyalinia alliana smelling strongly of garlic, 

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

 argument for the sense of smell in the creatm^es themselves. 



Position of Olfactory Organs in Pulmonata.^ — Most authori- 

 ties 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 creatiu'es were quite unable to discover the whereabouts 

 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 tur- 

 pentine, while another Helix, which was unmutilated, did not 

 object to the turpentine being held between its tentacles. 

 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 ospJiradium is in situation intimately connected with the 

 breathing organs, lieing generally placed near their base, with the 

 ^ E.g. Sochaczewer, Zcits. uiss. Zool. xxxv. p. .30. - ZooJ. An;:. 1882, p. 472. 



