No. 1, August, 1920] GENERICS 43 



pallida by the dropping of a single factor or set of linked factors. Standards and fulls of an 

 7ns appear to be controlled, both in form and in color, by independent sets of linked factors. 

 — J. Marion Shull. 



332. Bornmuller, J. Notizen zur Flora Unterfrankens nebst einigen Bemerkungen 

 uber Bastarde und eine neue Form von Polystichum lonchitis (L) Roth im Alpengebiet. [Ob- 

 servations on the flora of Unterfranken, with several remarks on hybrids and a new form of Poly- 

 stichum lonchitis (L) Roth in the alpine region. Beih. Biol. Centralbl. 36: 183-199. 1 pi. 

 1918.— See Bot. Absts. 4, Entry 1704. 



333. Boulenger, G. A. Un cas interessant de dimorphisme sexuel chez un serpent 

 africain (Bothrolychus ater Giinther). [An interesting case of sexual dimorphism in an African 

 snake.] Compt. Rend. Acad. Sci. Paris 168: 6G6-069. 1919.— See Bot. Absts. 5, 1 !ntry 1463. 



334. Brandl, J. Die direkte Anpassung und Vererbung der Pflanzen. [Direct adapta- 

 tion and heredity in plants.] Wiener Landw. Zeit. 68: 790. 1918. 



335. Brehm, V. Uber geschlechtsbegrenzte Speziesmerkmale der Siisswasserorganismen 

 und deren eventuelle experimentelle Aufklarung durch das Mendelsche Spaltungsgesetz. [On 

 the sex-limited species-characters of freshwater organisms and their experimental explanation 

 through the Mendelian law of segregation.] Naturw. Wochenschr. 18:4-8. 1919. 



336. Bridges, C. B., and T. H. Morgan. Contributions to the genetics of Drosophila 

 melanogaster. II. The second chromosome group of mutant characters. Carnegie Inst. Wash- 

 ington Publ. 278. P. 123-204, 7 pi., 17 fig. Washington, D. C. 1919.— 39 mutant races with 

 genes in "second chromosome" are described, paralleling treatment of sex-linked characters 

 in Carnegie Publ. 237; more than 35 others, discovered since 1916, remain to be described. 

 Most important genes, with loci, are: 



affects mainly eye-facets 

 affects mainly thorax pattern 

 affects mainly venation and legs 

 affects mainly body color 

 (pr) affects mainly eye color 

 65.0 Vestigial (vg) affects mainly wings and halteres 

 73.5 Curved (c) affects mainly wing curvature 

 96.2 Plexus (px) affects mainly wing venation 

 105.1 Speck (sp) affects mainly axil of wing 



Mutants are treated in chronological order of discovery; special attention is given to genetic 

 methods employed, and tracing their development. Each mutant is fully described as to 

 origin, stock, determination of chromosome and locus, reoccurrences, allelomorphs, modi- 

 fiers, literature, and value as a genetic tool. General topics, discussed under mutants to which 

 they apply, include: modifying factors, autosomal and balanced lethals, variations in cross- 

 ing-over due to age, temperature, and specific genes, causes of inviability and methods of 

 "balancing" inviability in experiments, coincidence and its bearing on map-distance, linkage 

 method of analysis for multiple-gene cases, etc. — Most of the mutants are recessive, i.e., the 

 heterozygote can not be distinguished from normal. Only five are dominant; at least four 

 of these are lethal when homozygous, like most dominant mutations in Drosophila. Some 

 (e.g., black, blistered, etc.) are partially dominant; i.e., the heterozygote is intermediate be- 

 tween homozygote and normal, but usually more like normal. Two of the genes (lethal T 

 and lethal Ila) show their presence only by disturbance of expected ratios, since they have 

 no visible effect when heterozygous, and kill all flies homozygous for them. Certain genes 

 are "specific modifiers," i.e., they produce no effect except in the presence of certain other, 

 "main" genes; thus cream II, cream b, and pinkish, all dilute eosin (sex-linked) eye color, 

 but produce no visible effect on non-eosin flies; again, one or more second-chromosome genes 

 reduce bristle number in dichaete (third chromosome), but not in non-dichaete, flies. Pur- 



