300 'Journal of Comparative Neurology and Psychology. 



tive, and is due to the position (extension or contraction) of the 

 thoracic appendages. If these have the "anterior position," the 

 reaction is positive; if they have the "posterior position," the 

 reaction is negative. These positions appear to depend upon the 

 intensity of hght which strikes the posterior lateral surface of the 

 eyes equally. 



9. The larvae orient to screens and backgrounds of black and 

 of w^hite by reflex movements identical with those by w^hich they 

 react to direct illumination and shading. 



10. The reactions by which the body-orientation to light is 

 produced, are invariable motor-reflexes, quite in accord with the 

 local action theory of tropisms. The reactions by which the pro- 

 gressive orientation to light is produced, although appearing to be 

 simple reflexes, are not invariable or constant, but dependent upon 

 "physiological states." 



11. In all the reactions to light (except the photopathic) the 

 body-orientation is of primary importance, since progressive orien- 

 tation cannot occur until the body-orientation has been established. 



12. None of the reactions to light can be interpreted as "a 

 selection from among the conditions produced by varied move- 

 ments." They are not trial (and error) reactions, in the sense 

 in which this expression is used by Jennings and Holmes. 



IX. LIST OF REFERENCES. 



Bell, J. C. 



1906a. The reactions of the crayfish to chemical stimuli. Journ. of Comp. Neurol, and 



Psycho!., vol. 16, p. 299. 

 1906b. Reactions of the crayfish. Harvard Psychological Studies, vol. 2, p. 615. 

 BoHN, Georges. 



1905a. Impulsions motrices d'origine oculaire chez les Crustaces. Bul.institut gen. psychol., 



no. 6, p. 1-42. 

 1905b. Attractions et ocillations des animaux marins sous I'influence de la lumiere. Institut 

 gen. psychol. Memoirs, i, p. 108. 

 Graber. 



1884. Grundlinien zur Erforschung des Helligkeits- und Farben-sinnes der Thiere. Prag 

 und Leipsig. 

 Hadley, p. B. 



1906a. The relation of optical stimuli to rheotaxis in the American lobster. Am. Journ. 



of Physiol., vol. 17, pp. 326-343. 

 1906b. Annual report of the Rhode Island Commission of Inland Fisheries for 1905, pp. 237- 



1907a. Galvanotaxis in larvae of the American lobster. Am. Journ. of Physiol., vol. 19, 



pp. 39-51. 

 1907b. Annualreportof the Rhode Island Commission of Inland Fisheries for i9o6,pp. 181-216. 

 1908. Reaction of blinded lobsters to light. Am. Journ. of Physiol., vol. 1.1.1, pp. 180-199. 

 Herrick, F. H. 



1896. The American lobster. U . S. Fish Commission Bull., vol. 15, pp. 1-252. 



