EYE PIGMENTATION IN INSECTS — BODENSTEIN 



33 



imaginal eye of the hemimetabolous insect, just as the eye disc is the 

 prospective anlage for the imaginal eye of the holometabolous insect. 

 Thus it should be theoretically feasible to detect the presence of dif- 

 fusible eye pigment precursors by the color reaction in the newly 

 formed facets of the eye, provided an eye-color mutant lacking the 

 brown eye pigment is available. We are fortunate to have in our Peri- 

 planeta americana cultures a mutant stock with white-yellow eyes. 

 The normal eye color of the American roach is a dark brown. Is the 

 lack of pigment in the eyes of the mutant roach caused by a genetic 

 block that prevents the formation of a diffusible intermediate metabo- 

 lite necessary for pigment differentiation? To test this, one should 

 transplant, as was done in Diptera, the nymphal eye, including the 



Table 2. — The influence of various implants on the testis color 



Type of 



donor 



Musca 



Musca 



Musca 



Musca 



Phormia 



Phonnia green 



Sarcophaga 



CalUtroga 



Callitroga 



Kind of tissue 

 transplanted 



eye 



Malpighian tubes 



ovary 



testis 



eye 



eye 



eye 



eye 



Malpighian tubes 



DL. kynurenine 



Host 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 

 Musca green 



Number 

 of cases 



2 



I 



3 



2 



3 

 4 

 3 

 4 

 3 

 9 



Effect on 

 testis color 



positive 



positive 



positive 



negative 



positive 



positive 



positive 



positive 



positive 



positive 



budding zone, from a white-eyed roach into the body cavity of a 

 normal wild-type roach. But technical difficulties preclude this method 

 of approach. However, it is possible to unite in parabiotic fusion two 

 nymphal roaches (Bodenstein, 1953). The fused partners soon grow 

 together, molt in synchrony after an appropriate interval and in ex- 

 ceptional cases are able to molt several more times. The blood circu- 

 lates freely from one partner to the other in such a parabiotic pair. 

 Therefore, any pigment precursor present in the blood of the normal 

 partner can pass into the mutant partner and will be able to exert its 

 effect here. The principle of this method is the same as that of trans- 

 plantation, for both are designed to allow diffusible substances in the 

 blood of the animal to come into contact with the developing eye 

 tissues. 



With this information as a background, the experiments performed 

 on Periplaneta can be discussed. They consist of five parabiotic pairs. 

 In each, a Qth-stage normal nymph was combined in parabiosis with a 

 younger (5th to 6th stage) nymph of the mutant white-eyed stock. 



