EYE PIGMENTATION IN INSECTS — BODENSTEIN 25 



for all experiments. This stage is easily recognized because the larva 

 empties its gut before forming the puparium. Larvae in which the gut 

 was almost or completely empty were selected for the operations. Such 

 larvae need not be fed. They were kept, according to the size of the 

 species used, two to four individuals together in small screw-top glass 

 vials (2.5x6 cm.) containing a strip of filter paper, at 25°C. room 

 temperature. 



The organ transplantations were made with a Drosophila injection 

 apparatus (Bodenstein, 1950). The desired organ discs or other larval 

 tissues were simply injected into the body cavity of the host larvae. 

 The organ discs of large donor species were sometimes cut in half 

 before they were transplanted. When Musca domestica was used as 

 host, the mortality following the operation was very low. Usually 

 up to 80 percent of the animals survived. In some series a 100-percent 

 survival rate was recorded. But not all the species used as hosts 

 withstood the operation this well. These cases will be discussed in 

 the appropriate place in the text. No special effort was made to quanti- 

 tate the amount of eye or testis pigment produced. Cases in which 

 eye-color changes occurred were recorded as positive, regardless of 

 the magnitude of the change, but it must be emphasized that the color 

 change in such positive cases was always clearly noticeable. In some 

 experiments an effort was made to grade roughly the observed eye- 

 color effects as strong, medium, weak, and none. Strong represents 

 an effect in which the color density almost resembles that of a normal 

 wild-type eye. 



The 3-hydroxykynurenine used in these experiments was prepared 

 and made available to us by Dr. Peter Karlson (Munich, Germany). 

 I am very grateful to him for his kindness in supplying this material, 

 especially since the commercially obtained compound proved to be 

 unsatisfactory. I would also like to acknowledge here my deep appre- 

 ciation to Dr. Karlson for many helpful suggestions and for his 

 stimulating discussions concerning the problems dealt with in these 

 communications. 



EXPERIMENTAL 



TRANSPLANTATION OF EYE DISCS BETWEEN WILD AND 

 GREEN-EYED MUSCA 



When the eye disc of a wild Musca larva is transplanted into the 

 body cavity of the same type host, the transplant, on the emergence 

 of the host, is developed to imaginal completion and shows the same 

 coloration as the eye of its host— i.e., that of a wild-type eye. When 



