296 Journal of Coiiiparatizr Xeurology and Psychology. 



sociations are very slowly acquired. The sensory elements 

 which enter into them are visual, tactual and kinesthetic. 

 Yerkes used a simple labyrinth, testing the frog's memory of a 

 path to water ; he kept records of time as well as of movements 

 made. A straight path was learned by a process of selection 

 from random mo\'ements of those which led to the desired 

 object. 



Yerkes' work on the crustaceans stands almost alone. 

 The green crab and the crawfish both profit a little by experi- 

 ence and learn simple labyrinth paths^ Bethe had shown that 

 Carcinus niaenas could not readily learn to inhibit deep-seated 

 instincts.- Spaulding ^ finds that hermit crabs profit by experi- 

 ence with considerable rapidity when visual and taste sensations 

 may be associated. 



Upon comparing the fish, the frog and the turtle ^ 

 Yerkes found that the turtle's associations were formed most 

 rapidly, a somewhat complex path being learned in five trials. 



Very little other experimental work has been attempted 

 with animals of this grade. Tkiplett "■ found that pe'-ches can 

 remember a glass partition wliich has been removed from the 

 aquarium. He verified the possibility of teaching pikes to in- 

 hibit their habit of devouring minnows (Moebius' experiment). 



Delboeuf - has observed lizards in captivity and finds that 

 they differ in disposition and intelligence. They can remember 

 people and places, and they seem to possess the higher emo- 

 tions as fear, love, jealousy. 



' R. M. Ykrkes and Gurkv E. Huggixs. Habit Formation in the Craw- 

 fish. Harvard Psychological Studies, Vol. I, 1902. 



Yerkes. Habit Formation in the Green Crab, Carcinus granulat us. Bio- 

 logical Hulli'tni, Vol. Ill, 1902. 



- Hethe. Das Centralnervensystem von Carcinus maenas. \\ Theil, Arch. 

 f. iiiikr. .hia/., Bd. LI, p. 447. 



■* E. G. SiwULDlNG. Association in Hermit Crabs, /our. Comp. Neurol, 

 an./ Psychol., Vol. XIV, p. 49, 1901. 



' Yerkes. Formation of Habits in the Turtle. Pop. Sci. Mo., LVIII, p. 519, 

 •1901. 



^ Tripeett. The Educability of the Perch. Amer. Jour. Psychol., Vol. 

 XII, p. j;54, 1901. 



♦J 1 )EEBOEi'K. The Aflections and Jealousies of Lizards. Pop. Set. Mo.^ 

 Vol. L, 1897 and Revue Scientifique, Vol. IV, pp. 363-367, 690 and 805. 



[ 4] 



