104 HOMING AND RELATED ACTIVITIES OF BIRDS. 



The position habit was carried over for this one trial, then gave way as 

 follows, 100 per cent correct: 



Light right, response right. 

 Light right, response right. 

 Light right, response right. 

 Light left, response right. 

 Light right, response right. 



Light right, response right. 

 Light left, response right. 

 Light right, response right. 

 Light left, response right. 

 Light right, response right. 



The results from all of the tests seem conclusive to the author. Somewhere 

 in the neighborhood of X = 7120, under the conditions of the present test, we 

 find the limits of sensitivity. This is practically the limit we obtained for 

 the chick (see p. 94). 



RESUME OF TESTS ON PIGEON. 



(1) The range of spectral sensitivity in the homing pigeon lies approxi- 

 mately between X = 4200 and X = 7120. It was not our purpose to determine 

 the limits with any great degree of exactness, since they are dependent to 

 some extent upon adaptation and upon the absolute intensity of the ray of 

 light expo.sed. 



(2) The homing pigeon is not sensitive to infra-red rays, at least to those 

 which have approximately a length of X = 8000. Since neither a quartz nor 

 a rock-salt prism was at our disposal we could not give an ultra-violet light of 

 any intensity. The evidence on the violet end is clear, however, in view of the 

 fact that the efficiency of the violet rays falls off apparently somewhat more 

 rapidly for the pigeon than even for man. 



(3) Hess is unquestionably wrong when he states that the pigeon is " blind 

 to blue and violet." We have shown the contrary quite clearly, even in the 

 notes which we have presented in this paper. Our unpublished data show 

 that this animal is sensitive to all wave-lengths between the limits expressed 

 in (1) above. 



(4) The young pigeon is positive to light, but is not so automatic in its 

 responses as the young chick. 



