( 
186 GENETICS: C. B. BRIDGES Proc. N. A. S. 
droxide, and the lysine as picrate. The residual solution contained an 
amount of non-amino nitrogen corresponding approximately to that 
determined by Van Slyke's method in excess of the arginine and histidine 
non-amino nitrogen. 
Attempts to crystallize the free base or its derivatives have been success- 
ful only with the phosphotungstate. Recrystallization of the phospho- 
tungstate yields a product in which the ratio, Total N : Amino N = 2:1. 
The free base prepd. from the recrystallized phosphotungstate is hy- 
groscopic, and decomposes slowly when dried at 100 °. It does not appear 
to be a peptide, for the ratio of amino to total nitrogen is not increased 
by boiling 40 hours with 20 per cent hydrochloric acid, nor by heating 8 
hours in a bomb tube at 125° with 25 per cent sulfuric acid. We are 
engaged in the preparation of larger amounts of the substance in the 
hope of determining its structure. 
1 Literature quoted by D. D. Van Slyke, /. Biol. Chem., 10, 1911 (15). 
2 Koessler, K. K., and Hanke, M. T., /. Biol. Chem., 39, 1919 (497). 
GENETIC AL AND CYTOLOGIC AL PROOF OF NON -DISJUNCTION 
OF THE FOURTH CHROMOSOME OF DROSOPHILA. 
MELANOGASTER 1 
Bv Calvin B. Bridges 
Carnegie Institution of Washington 
Communicated by T. H. Morgan, March 18, 1921 
A mutant type of D. melanogaster known as "Diminished" gave genet- 
ical results which proved the involvement of a "deficiency," 2 i.e., a multi- 
local loss of genes, in the chromosome corresponding to the "fourth linkage 
group" 3 ' 4 (see section I). Further exceptions to normal inheritance 
showed that non-disjunction 5 of this chromosome had occurred giving rise to 
(Diminished) individuals lacking one member of the fourth-chromosome 
pair (see section II). The deficiency in this case consisted therefore in 
the loss of an entire chromosome. The haploid nature of Diminished 
was then proved cytologically : it was found that in the cells of Diminished 
individuals only one small round chromosome was present instead of a pair 
(section III). This finding demonstrates the correctness of the view that 
the carrier of the genes of the fourth linkage group is the small round 
chromosome. A positive direct proof is provided that a particular auto- 
some is the carrier of the genes of particular non-sex-linked Mendelian 
characters. 
I. The features that in the aggregate prove that a deficiency is involved 
are: 
