100 CORA D. REEVES 



PoSTvSCRIPT 



While this paper was being made ready for the press in 

 the fall of 1917, Doctor Reeves took up her residence 

 at Ginling College, Nanking, China. War has delayed 

 the publication. Owing to Br. Reeves' absence and the 

 lapse of time I am venturing to add the following notes 

 for which I alone am responsible. 



1. The absorption of rays of the visible spectrum by the 

 water of Wisconsin Lakes has been recently studied by 

 Pietenpol (Trans. Wis. Acad. Sci., XIXI (1918), 562-593). 

 In connection with the discussion on pp. 74-75, it seems 

 best to record here a recent simple experiment of my own 

 on the visibility of red through lake water. In February, 

 1919, when Winan's Lake in Livingstone Co., Mich., was 

 covered by about eight inches of clear ice, without snow, 

 I suspended through a hole in the ice and at a distance of 

 three feet below the surface a cylindrical tin can covered 

 with red paper (Klinksieck's color code No. 56). At a 

 distance of thirteen feet from this hole was a small spear- 

 house which shut off a good part of the light from a second 

 hole cut through the ice which formed its floor. By means 

 of a mirror immersed to a depth of a foot through this 

 hole I was able to view the can. Its color, as thus viewed, 

 was unmistakably bright red, merely a little duller than 

 when seen through air. The red rays which reached my 

 eye had travelled a distance of 16 feet through water. 

 With the great sensitivity of fish to red I have no doubt 

 that it stimulates them through this lake water at much 

 greater distances. 



2. Miss Gertrude Marean White (Jour. Exp. Zool. Vol.27, 

 pp. 443-498, 1919) has recently published an account of 

 ingenious experiments on color vision in sticklebacks and 

 mud-minnows. The m.ethods used were those of the third 

 training procedure (this paper p. 81) and the results reached 

 are those of other investigators except Hess and are in 

 accord with those of Doctor Reeves. They do not involve 

 the equation of brightness through the behavior of the fish 

 and are therefore open to the same criticism as other ex- 

 periments of their type. Miss White also reports ex- 

 periments on the inability of these fish to discriminate 

 grays of very unequal brightness and in this respect con- 

 firms Doctor Reeves (this paper pp. 20 and 37). 



