EYE PIGMENTATION IN INSECTS — BODENSTEIN 27 



The nonautonomous character of pigment development in the eye 

 of the green mutant is also well illustrated by the transplantation of 

 the two eye discs from the same green donor larva into two different 

 larval hosts — one a green, and the other a wild-type host. Nine such 

 paired transplantations were performed, but only four pairs in which 

 both host partners survived were available for study. They showed 

 that the eye discs in the green hosts always developed their own char- 

 acteristic color — i.e., they remained yellowish green, while the partner 

 discs in the wild hosts gave rise to eyes with wild-type pigmentation. 

 Since the discs used came from the same donor larva, they were 

 strictly comparable ; this experiment is therefore an especially con- 

 vincing demonstration of the dependency of the green eye for its color 

 development on a diffusible factor in the wild-type host. 



RELEASE OF DIFFUSIBLE SUBSTANCES FROM OTHER ORGAN TISSUES 



The observation that the eyes of a green host can be made to de- 

 velop color after the transplantation of a wild-type eye disc indicates 

 that the substance responsible for this effect is released by the trans- 

 planted eye tissue. The question whether other tissues as well can 

 bring about a similar effect was tested by implanting other organs or 

 organ discs of wild-type larvae into green hosts. It was found that 

 the eye color of green hosts remained unchanged after transplantation 

 of antenna (7 cases), leg (8 cases), and haltere (i case) discs. Testis 

 transplants were also negative. However, the implantation of one wild 

 ovary caused a slight color change in the eyes of two out of seven 

 hosts tested. A very strong positive effect was produced after trans- 

 plantation of Malpighian tubes (18 cases). One Malpighian tube 

 changed the host eyes to red, while the implantation of two Malpighian 

 tubes made them almost indistinguishable from wild-type eyes. An 

 equally strong effect was obtained by transplanting Malpighian tubes 

 from Callitroga larvae (4 cases) into green-eyed Musca mutants. The 

 fact that ovary as well as Malpighian tube implants modify the eye 

 color of the green host shows that the responsible substance is pro- 

 duced not only by the eye tissue but also by other parts of the body. 

 The weak effects of the ovary transplants are perhaps not so difficult 

 to understand if one recalls that one eye implant also often fails to 

 change the host eye color. A single organ disc is apparently not suffi- 

 cient to produce the amount of substance necessary for a clear color 

 effect. Whether the ineffective organs, as for instance the leg discs, 

 produce the diffusible principle below threshold or not at all is not 

 known. As gaged by the strong eye-color effects, the Malpighian tubes 



