166 PHYSIOLOGICAL GENETICS 



other eye-color types develop their own color after transplants 

 tion. But vermilion and cinnabar disks grown in claret, carna- 

 tion, and a IVw other mutants develop either vermilion or a color 

 between this and Wild. The authors (1937c) then proceeded to 

 test eyes containing two recessive colors, one being vermilion. 

 It has been mentioned previously that vermilion-garnet is 

 yellowish. This would mean that there is a considerable 

 insufficiency of /'' -substance, which could be tested in appropriate 

 transplantations. The results were: 



1. live disks of double recessives, one being vermilion, im- 

 planted into Wild-type hosts. In all cases, the color was that 

 of the other mutant (not vermilion). 



2. Eye disks of the second mutant implanted in vermilion 

 hosts. Some develop their genetic color; others, a lighter color; 

 and some, a much lighter color; but none so light as the double 

 recessive. (There is also a sex difference.) 



3. P]ye disks of the different mutants transplanted into hosts 

 double recessive for the same mutant and vermilion. The 

 results are parallel to those under 2. 



4. Young Wild-type disks implanted in older vermilion hosts 

 developed intermediate pigment. 



The first set of these experiments agrees with the assumption 

 that the Wild-type host furnishes the missing v + -substance 

 without which no vermilion develops. In the second group, 

 wherever the genetic color appeared, the implant must itself 

 contain the necessary v + -substance ; where, however, lighter 

 colors appeared, the mutant eye could not have a sufficient 

 amount of this substance. The third group shows the same 

 thing, but it is surprising that the double-recessive host does not 

 supply any v+-substance, which ought to be produced by the 

 Qonvermilion gene. It is probable that such experiments will 

 lead to further insight if put on a quantitative basis. The 

 present situation is conceived by Ephrussi and Beadle (19376) 

 in the following way: When a Wild-type eye disk is grown in a 

 mutant host and develops the mutant color, a substance is 

 supposed to be lacking or deficient that is needed for Wild-type 

 development. By checking different combinations against each 

 other, three such substances have been found which were called 

 v + (missing in vermilion), cn + (missing in cinnabar), ca + 

 (missing in claret). These substances are supposed to be formed 



