250 S. B. VINCENT 



ness are the only visual conditions which to any considerable 

 extent control the activity of the animal." 3 



Mr Waugh 4 has studied vision in the white mouse. Neg- 

 lecting for the time his experiments and conclusions on coloi 

 vision let us consider those on form and distance. The forms 

 to be discriminated were a circle and a cross, cut in black card- 

 board and illuminated by lights from behind. He only finds 

 discrimination present in one instance, and in this case the 

 per cent, of right choices in 130 trials was only 69+. He does 

 not give us the exact order of alternating the forms. May not 

 this rat have partly learned the order? 



He tested distance discrimination by having animals jump 

 from a wooden disk set at different heights above a table whose 

 surface was varied in color. The time elapsing between the 

 placing of the animal and the jump was taken as an evidence 

 of the animal's ability to discriminate distance. In the first 

 experiment the time increased with the distance, but in the 

 second and third, where there was a glass surface over the 

 'table below, the time was unusually long even when the dis- 

 tance was not increased above 10 cm. 



Mr. Waugh anticipates the objections to taking the time of 

 the reaction as proof of the discrimination of distance, but he 

 says nothing about olfaction which is also a distance sense and 

 probably a very keen one in these animals. The very fact that 

 glass, which is as non-odorous as anything we know, should 

 present such difficulties would suggest an odor criterion in 

 this case. 



He speaks of the short range of vision in the mouse, but gives 

 no anatomical data to support this belief and his experiments 

 with depth give none. ' 



His results were practically negative so far as the discrimina- 

 tion of either form, distance or depth were concerned, but he 

 neglected, as others who have experimented with animals have 

 neglected, to establish first a normal focal distance or distance 

 of accommodation. The distances at which Mr. Waugh tried 

 his animals for discrimination of depth were 2, 4, and 6 in. 



3 Yerkes, R. M. The Dancing Mouse. New York, 1907, p. 198. 



4 Waugh, K. T. The Role of Vision in the Mental Life of the Mouse. Jour, of 

 Comp. New: and Psych., 1910, Vol. 20, p. 570. 



