THE NATURE OF THE GENE 313 



number of phenotypes. Some of these behave genetically like 

 ordinary new mutants, a considerable number of others being 

 identical with known standard mutants. If this had not occurred 

 in pedigreed and controlled lines but in an ordinary stock, 

 the impression of a series of simple gene mutations would have 

 been created. Actually a similar case found by Plough and 

 Holthausen (1937) has been interpreted as mass mutation of 

 genes. There are cases in which a number of well-known mutants 

 occurred in a way that is rather suggestive of a similar origin. 

 For example, in Drosophila, truncate originated in a Beaded 

 stock; vestigial and balloon, from truncate; spread, from Beaded 

 and vestigial; purple, from vestigial; kidney, from vestigial X 

 purple; ebony, from balloon. Blistered, jaunty, and curved 

 came from rudimentary (two of which we found to be produced 

 by a rearrangement). Many new mutants appeared among the 

 progeny of crosses between other mutants. 



h. It is most remarkable that rearrangements within certain 

 areas have a similar phenotypic effect and might therefore be 

 described as different multiple allelomorphs, e.g., a number of 

 deficiencies near the locus plexus produce so-called plexates. 

 Probably some translocations in this region have a similar effect. 

 Duplications and translocations in the Bar region produce the 

 Bar effect; different deficiencies in the fused region, notch effects; 

 point mutations and translocations in the yellow region, yellow 

 color. The similar phenotypic effect of different happenings 

 at one point or in a more or less long chromosome section near 

 this point may in these cases be due to a so-called mutation, a 

 deficiency, a translocation, a duplication. 



i. There are cases in which the end members of a series of 

 multiple allelomorphs are suspected or known to be deficiencies 

 (vestigial, eyeless). There are other series of multiple allelo- 

 morphs with an additional deficiency appearing as a member of 

 the series, e.g., bobbed. 



j. There are certain changes that occur at many different 

 points of different chromosomes, producing a similar phenotypic 

 effect. The minutes in Drosophila are such changes, which in 

 part are certainly deficiencies and in part not visibly different 

 from gene mutations. 



k. There are a few extremely typical "mutants" that we have 

 discussed in connection with the cases of homoeosis. They are 



