THE MUTATED GENE 187 



transplanting it to a Wild-typo host, the host is supposed to 

 furnish a substance (or hormone for its production) absent in a 

 j-fly, a # + -substanee. The same argumentation applies to a 

 cn + -substance, which is proved to be different from the ^-sub- 

 stance, because a y-disk in a cn-host gives a Wild-type eye. In 

 the Wild type, these substances are produced within the eye. 



Recently Ephrussi, Clancy, and Beadle (1936) demonstrated 

 the presence of this stuff in the lymph by injecting Wild-type 

 lymph into apricot-vermilion pupae. The flies hatched with 

 apricot eyes. It turned out that the stuff is produced in pupae 

 30 to 80 hr. old and acts upon pupae from before pupation up 

 to 70 hr. after pupation. 



The results regarding the claret character had shown that a 

 genetically Wild-type eye could not become Wild type in a 

 claret host; there must also be a ca + substance, necessary for 

 Wild type, which, however, is not formed in the eye itself. 

 But as a ca-type eye in a Wild host does not become Wild type, 

 there must also be something in the ca-effect within the eye that 

 prevents Wild-type pigmentation. These three substances must, 

 however, be closely related because the absence of one usually 

 entails the absence of all. From these and other facts the authors 

 conclude that the three substances are successive products of a 

 chain reaction: ca + — > v + — * cn + . The different mutant genes 

 then produce either an interruption of this chain at some 

 point or a retardation of its rate. In this way — which links 

 these facts with our former discussions on rate — the details 

 of all experiments may be explained. (See, however, foot- 

 note, p. 167.) 



Recently (1937), Medvedev has used the Ephrussi-Beadle 

 method for transplanting wing disks of mature larvae belonging 

 to Wild type, yellow, ebony, and black into different hosts in 

 different combinations. The result was always autonomous 

 development, which means a negative result from the standpoint 

 of this chapter. 



At this point also an example from the plant kingdom may be 

 inserted. Anderson and de Winton (1935) in studying the 

 manifold action of some genes in Primula found that the genes 

 Ch increase in the flower sepal and petal lobing; the gene t 

 inhibits it; and both have an inhibiting effect upon peduncle 

 elongation, though at opposite ends of the peduncle. They think 



