Wilson S. Stone

The Evolutionary Biology of the Hawaiian Drosophilidae

Grimshaw (1901, 1902) and Perkins (1910) first focused the attention of dipterists on the aberrant characteristics and abundance of the Hawaiian Drosophilidae. They described 47 species; additionally, Perkins’ extensive descriptions (1913) of the biotic habitat in which the insects live alerted biologists to the unique but unknown ecology of the flies.

Mutations and Mutagenic Agents in Bacteria

As previously reported, mutation to penicillin or streptomycin resistance can be induced in Micrococcus aureus by growing the organism in nutrient broth and in certain synthetic media which have been irradiated with ultra-violet light (Stone, Wyss, Haas, 1947) or treated with hydrogen peroxide (Wyss, Stone, Clark, 1947; Wyss, Clark, Haas, and Stone, 1948). Stone, Haas, Clark, and Wyss (1948) showed that these mutations result from an increase in mutation rate and are not due to selective action in favor of pre-existing mutants in the culture. The penicillin and streptomycin resistant mutants grow no faster than the original strains in either irradiated or unirradiated media. Mixtures of normal and mutant Micrococcus aureus exhibited the sam-e ratio after growth in irradiated and unirradiated media that they had before growth. Penicillin resistant mutants had no more resistance to streptomycin than did their original parent strain. When these penicillin resistant mutants were grown in irradiated broth or hydrogen-peroxide-treated broth the treatment induced mutation to streptomycin resistance in these at the same rate as that induced in the normal strain. The same characteristics hold for the streptomycin resistant mutants. In attempts to characterize the mutating principle, and to determine the method of its production by ultra-violet irradiation or hydrogen peroxide treatment, we have investigated some of the physical properties of treatment of the substrate, and of the treated substrate itself.

Linkage between the X and IV chromosomes in drosophila melanogaster

Summary1)When these translocations are heterozygous with normal, the usual reduction of crossing-over is found near the break.2)In the homozygous condition, the amount of crossing-over in those regions of the chromosome moved nearer to a spindle-fibre is reduced even below that of the corresponding regions in the heterozygous condition. The percentage of crossing-over in the regions on the other side of the break, unchanged in position with reference to a spindle-fibre, either is not appreciably changed, or is even higher than the control.3)In mixed crossing-over, the crossover value of each region is about the same as the lowest crossover value of the component translocations heterozygous with normal.4)All hyperdiploid combinations survive. Also, males hyperploid for various limited regions survive, although none are fertile except those involving only the cut locus. Females hypoploid for any section are viable whenever males hyperploid for that section live.5)Non-disjunction is very frequent for the left fragment.

Gasometric determination of hydrogen peroxide.

Summary Determinations of the peroxide content of irradiated broth using catalase in a Warburg respirometer were found to be inaccurate. In the presence of excess catalase the oxygen evolved approaches a value of twice that indicated by the accepted general equation for enzymatic decomposition of H2O2; if too little enzyme is used the reaction is slow and incomplete. The method is unsatisfactory for the quantitative determination of peroxide.