424 JOHN B. WATSON 



viously kept in the dark there is a corresponding rich formation 

 of the bleaching products. The building up process is at first 

 not able to repair the waste. Adaptation follows, and the build- 

 ing up process not only compensates for the waste, but con- 

 tinues until the retina which was bleached under the influence 

 of the strong light again becomes red. There is an upper limit 

 to the speed of the restitution process. If the decomposition is 

 increased overwhelmingly, even the greatest activity on the 

 part of the epithelium fails to restore equilibrium, and the 

 retina remains bleached out. Only a decrease in illumination 

 can restore the purple. After a more complete adaptation the 

 "purpling" processes continue, but with lessened activity. In 

 continued darkness the regeneration processes cease, probably 

 in consequence of the lack of the by-products necessary for 

 their arousal. 



Birds. Hess (13) (p. 443) confirms by a new method his 

 former conclusion that light-adapted day birds have an exten- 

 sion in the red end of the spectrum coincident with man's, but 

 that the blue-greens, blues and violets have low stimulating 

 value. The explanation of this is to be found in the reddish- 

 yellow oil globules which are to be found in the retina of birds. 

 These absorb the short but admit the long rays. It will be 

 remembered that he in his earlier paper maintained the view 

 that the hen has visual qualities similar to those of the human 

 being, but that due to the presence of the oil globules there are 

 certain differences in behavior. All these differences between 

 hen, and man with normal vision, are smaller than between the 

 hen and the totally color-blind or red-green blind man. I quote 

 his own words (p. 445) on the coloring of the rice kernels for 

 tests on the color blindness of the hen. I am in some doubt as 

 to his meaning, or if I get his meaning, of the possibility of 

 obtaining any such color equations: "Um Hiihner nach dem 

 Prinzip der Seebeck-Holmgren'schen Wollprobe mit farbigem 

 Futter zu untersuchen, farbte ich grossere Mengen von Reis- 

 kornern mit verschiedenen Pigmenten so, dass mir insbesondere 

 gelblichrote, angenahert rein rote und blaulichrote, sowie gelb- 

 lichgrune, angenahert rein grime und blaulichgriine Korner teils 

 in schon freien, teils in mehr oder weniger stark mit Weiss, 

 Grau oder Schwarz verhiillten Farben, ferner gelblichgraue, rein 



