CHEMORECEPTION: LOCOMOTION AND ORIENTATION 



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Figure 3 Ventral aspect of the head of Scyliorhinus. The nasolabial groove leads from 

 the upper edge of the mouth to the posterior (median) naris. Redrawn from Allis (1919). 



of basal cells (Andres 1966, Graziadei and Metcalf 1971). No specific in- 

 formation is available on this process in elasmobranchs. 



Although in most species studied the olfactory vesicles bear only cilia, in 

 some species microvilli are present as well, and in some teleosts certain types 

 of olfactory cells carry microvilli but no cilia (Bannister 1965). In Rhino- 

 batus lentiginosus, the guitar fish, the olfactory cells have a single apical 

 dendrite ending in an enlarged bulb, protruding above the surface. Although 

 this bulb carries short villi-like protrusions, there are no cilia (Reese and 

 Brightman 1970) (Figures 4, 5). 



It has been assumed (Parker 1922) that the cilia, and possibly also the 

 microvilli, carry the receptor sites for chemical stimulation, so that the in- 

 creased area of exposure created by the presence of cilia and microvilli may 

 be related directly to olfactory sensitivity and acuity. However, removing 

 cilia from the vesicle did not eliminate action potentials in response to odor 



