PREFACE

The last exhaustive compilation of genetic variations of
Drosophila melanogaster was "The Mutants of
Drosohpila melanogaster" prepared by Calvin B. Bridges 
and Katherine S. Brehme; it was published in 1944 and
was complete through 1942.  This volume is a revision of their
work; it contains new information on variants already described
and descriptions of variants discovered since 1942; it is
reasonably complete through 1966.
The new material was extracted from the literature, from
Drosophila Information Service, and from voluminous
contributions of unpublished material supplied by Drosophila
geneticists throughout the world.  The revision describes
genetic material currently available to Drosophila geneticists
and extinct material that may be encountered in earlier
literature on the subject.

The work of Bridges and Brehme was divided into two sections,
one describing wild-type stocks and the other describing the
known departures from the normal genotype.  Our revision is
divided into seven sections:  (1) mutants, with about 3000
entries; (2) chromosome aberrations, more than 1500 entries;
(3) special chromosomes, i.e., multiply marked chromosomes,
balancers, compound chromosomes, Y derivatives, and
X-Y combinations; (4) cytological markers; 
(5) departures from diploidy; (6) nonchromosomal inheritance; and
(7) wild-type stocks.  All except the first two groups have
relatively few entries.

Several new categories of effects unknown or nearly so in 1942
are included here.  (1) Pseudoalleles:  the intensive
investigations into pseudoallelism and complementation dating
from the pioneering work of E. B. Lewis on Star and astroid
(1945, Genetics 30:  137-66) have produced information on the
genetic fine structure of many loci.  (2) Isozymes:  a series
of genetically controlled enzyme polymorphisms and deficiencies
described mostly in the last decade; their discovery was made
possible by the development of gel electrophoresis.  
(3) Compound chromosomes:  formed by the attachment of two doses
of one chromosome arm to a single centromere; represented by
only the attached-X chromosome in the original edition,
the various classes of compound chromosomes now available
occupy an entire subsection.  (4) Marked Y 
chromosomes:  Y chromosomes marked by the genes carried on 
small attached euchromatic segments derived from the X or an
autosome.  (5) Reciprocal translocations between the X
and Y chromosomes.  (6) Attached 
XY chromosomes:  chromosomes with the portions of 
the X and Y chromosomes necessary for male viability and fertility 
attached to a single centromere.


Development of the system of nomenclature designating genetic
variations of Drosophila melanogaster has been rather
haphazard; consequently, the system is not a logical structure
but is replete with relics, redundancies, and inconsistencies.
Revision into a consistant scheme is not practicable, creating
as it would a chaotic discontinuity in the literature.  Even
were such a revamping considered desirable, design of such a
system is not obvious, since a change proposed to obviate one
inconsistency would likely create more conflicts than it
alleviated.  Therefore, with few exceptions, we have adhered
to the conventions established by Bridges and Brehme in the
original volume.  Some changes were made to correct glaring
inconsistencies and others to facilitate automatic handling of
Drosophila symbols.

July 1967

The conventions adopted for naming and symbolizing different
types of genetic changes are discussed at the beginning of the
different sections of the book.  Symbols of all genetic
variants both normal and abnormal are always italicized but
their names in text are printed in roman.

We are grateful to our colleagues throughout the world for
their cooperation in making available to us their unpublished
observations and in responding to our numerous queries.
Special thanks are due Doctors E. G. Lewis, the late 
H. J. Muller, J. Schultz, and A. H. Sturtevant, who
served as an informal board of consultants.  They have
contributed a measure of success to this effort but bear no
responsibility for its shortcomings.