Conipctisaforv Motions 463 



a The compensatory movements of the frog's head set up by 

 rotation arise in response to two distinct sets of stimuh, visual and 

 dynamic. 



b The response to the visual stimulus is relatively feebler and 

 slow^er than that to the dynamic stimulus. 



c The organ for the perception of the dynamic factor is prob- 

 ably located in the internal ear. 



d The dynamic perception involves a rotation or turning 

 element in the stimulus, as distinguished from an acceleration or 

 movement in a simple direction. 



I wish to express my sincere thanks to Prof. T. H. Morgan for 

 the helpful suggestions and encouragement that have made this 

 study possible; and to Prof. A. P. Wills for his assistance in eluci- 

 dating to me the mechanics of rotation. 



7 REFERENCES AND BIBLIOGRAPHY 



1828 Flourens, Marie Jean Pierre — (i) Experiences sur les canaux semicir- 

 culaires de I'oreilles dans les oiseaux. Memoirs de I'acad. roy. des 

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 (2) Experiences sur les canaux semicirculaires de I'oreilles dans les mammi- 

 feres. Memoirs de I'acad. roy. des sci. 9:467-477. 1830. Read 

 before the Academy, 13 Oc, 1828. 



1842 Flourens, M. J. P. — Recherches experimentales sur les proprietes du 

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1846 Prechtl, Johann Josef — Untersuchungen iiber den Flug der Vogel. 

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1866 Manoyer, M. — Recherches experimentales sur la locomotion chez les 

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1868 Leydig, F. — Ueber Organe eines sechsten Sinnes. Dresden. 



1869 GoLTZ, Fr. — Beitrage zur Lehre von den Functionen der Nervencentren 



des Frosches. Berlin, Hirschwald. pp. 130. 



1870 GoLTZ, Friedrich — Ueber die physiologische Bedeutung des Ohrlaby- 



rinths. Pfliiger's Archiv. 3:172-193. 

 ScHULZE, Franz Eilhard — Ueber Sinnesorgane der Seitenlinie bei Fischen 

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