ZOOLOGY AND BOTANY, MIOBOSCOPY, ETC. 31 



Eudimentary Sight apart from eyes.* — Prof. V. Graber has in- 

 stituted experiments to ascertain whether, and if so to what extent, 

 eyeless and blinded animals are sensitive to light. As an example of 

 the former he chose the earthworm ; for the latter, Triton cristatus. 



The worms were placed in a box containing a number of cells of 

 equal size, each with front and hind wall made of glass ; the whole 

 box was further divided into three parts, each of which had two front 

 and two hind windows ; the latter were turned from the light ; and 

 one of the windows of each cell was darkened, or supplied with a 

 differently coloured light from that of the others. At the bottom of 

 each was placed a layer of mud not sufficient to conceal earthworms. 

 Twenty to thirty worms were first put into each cell and the box placed 

 with one side towards a window with a north light. The number of 

 worms found on the light and the dark sides respectively were counted 

 at the end of every hour, and were replaced by fresh every four hours. 

 Seven readings show that 40 specimens were found in the light, and 

 210 in the darkened spaces, giving a proportion of five of the latter 

 to two of the former. 



Using opaque glass for one set of windows, 326 worms were 

 found in the partitions thus relatively darkened, and 204 in the 

 absolutely light ones. In employing light of different colours, care 

 was taken that the one colour chosen should bevery decidedly lighter 

 than the other. As it soon became evident that red was more 

 attractive to the worms than blue, a much darker shade of blue was 

 chosen than that of the red; then in 12 divisions 193 specimens 

 were found in the pale red light, and only 57 in the dark blue ; this 

 difference is the more remarkable as the worms, being naturally 

 lovers of darkness, would, so far as intensity of light was concerned, 

 have been expected to prefer the dark blue ; it indicates an apprecia- 

 tion of the quality of the light. In like manner, white light, deprived 

 of the ultra-violet rays, attracted 87, ordinary white light only 13 

 worms; of pale green and dark blue, the former colour attracted 

 138, the latter 42 individuals ; of pale red and dark green, the former 

 attracted 168, the latter only 72. In examination of a statement, that 

 it is only the anterior end of the body which is sensitive to light, 

 experiments were made upon worms deprived of this part to a length 

 of four or five rings ; they gave the proportion of worms found in the 

 dark as 2-6 to 1 of those in the light, and that of those in red 

 light as 2 • 8 to 1 of those ia the blue — results tending in the same 

 direction as those obtained from entire specimens. Applying the 

 same method to newts, Graber found that while, of 160 uninjured 

 specimens, only one was found in the light area, the rest being in the 

 dark, 135 specimens from which the eyeballs together with a con- 

 siderable length of the optic nerves had been removed, were found 

 in the light, and 308 in the dark. The same result was obtained 

 after the filling up of the eye-cavity by wax in some of the blinded 

 animals, proving that the optic nerve had no action in producing 

 this light-sensitiveness. Using coloured light, it was found that 192 



* SB. K. Akad. Wiss. Wien, Ixxxvii. (1883) p. 201. Cf. Naturforscher, xvi. 

 (1883) pp. 437-9, and ' Joum. of Science,' v. (1883) pp. 727-32. 



