CHEMORECEPTION: LOCOMOTION AND ORIENTATION 285 



support in a theoretical and philosophical polemic with the chemosensory 

 expert of the period, W. Nagel. The latter had maintained, in a lengthy 

 treatise (Nagel 1894) that chemical perception in water could be mediated 

 only through taste and the "general chemical sense," a viewpoint stated 

 earlier by Dumeril (1807a, b) and Weber (1847) but shown to be incorrect 

 by Aronsohn (1886). In passing, it should be mentioned here that the prob- 

 lem was studied by several workers over the next 25 years; the question was 

 definitely settled when Matthes (1924a, b) demonstrated that in Triton 

 olfaction functions equally well in the terrestrial and aquatic stages of the 

 life history of this animal. 



Von Uexkiill had observed earlier that starved sharks display high olfac- 

 tory sensitivity. He deprived six animals of food for several weeks after 

 removing, by scraping, the olfactory epithelial surface in two of the subjects. 

 These anosmic animals remained motionless and never reacted to food (dead 

 but fresh fish) placed in front of their nostrils. The normal shark, on the 

 other hand, started search movements with 3 to 6 min. They also became 

 greatly excited when von Uexkiill, after manipulating food fish, rinsed his 

 hands in the aquarium. 



Von Uexkiill attempted, probably for the first time in sharks, to experi- 

 mentally distinguish gustation from olfaction. For example, he observed that 

 mashed fishbait mixed with quinine was as readily located by the shark as 

 normal bait, was taken into the mouth, but then spit out. The bait was 

 ingested only after it had remained in the water long enough for the quinine 

 to be washed out. The author concluded that the quinine stimulated the 

 chemical sense of the mouth but not that of the olfactory surface and that 

 both taste and olfaction were involved in the observed behavior. He con- 

 sidered, however, that bitter food was not a normal stimulus situation and 

 that in natural conditions a nutrient item would be localized by an animal, 

 while an inedible one would not. For example, the apparently noxious 

 marine slug, Aplysia, is normally ignored by these shark, but when active 

 search was excited by placing food fish near such a snail, several sharks 

 captured it but readily spat it out again. 



Von Uexkiill interpreted these results as confirming the lack of olfactory 

 stimulation by snail substance and attributed the "erroneous" capture to 

 poor visual discrimination between the food fish and the snails. It is of 

 interest that the indiscriminate capture and even ingestion of nonfood items 

 by sharks has often been reported. Additional observations by the same 

 author refer to the effects of currents on the search movements of the 

 animals and to the occurrence of spiral pathways in the course of searching. 

 Although descriptive, these observations are of particular interest in connec- 

 tion with recent analyses in this laboratory of such search movements, which 

 will be referred to later. 



Frequently quoted observations, all made within a period of a few years 

 (Parker and Sheldon 1913; Sheldon 1909, 1911; and Parker 1909, 1912, 

 1914), essentially confirmed Bateson's and von UexkiiU's findings and estab- 

 lished the significance of olfaction in recognition and procurement of food 

 by sharks. Sheldon (1911) demonstrated that Mustelus will locate and attack 



