March, 1920] 



GENETICS 97 



658. Plate, L. Vererbungsstudien an Mausen. [Inheritance studies on mice.] Arch 

 Entwicklungsmech. Org. 44: 291-336. 5 fig. 1918.— Author presents results of studies on 

 sable and piebald patterns in mice. He concludes that the sable pal tern is due to a mutation 

 of the factor for yellow. He finds that sables, like yellows, arc always heterozyg> us, that 

 they often change into yellows in the course of their life and that they frequently produce 

 or are produced by yellows. He considers that the yellows in these cases really possess the 

 factor for sable but that the production of black pigment is inhibited by independent modi- 

 fiers. He finds that heterozygous chocolate and pink eyes have modifying influences of this 

 kind. The agouti factor is represented as independent of the black-yellow-sable series 

 (y, Y, Y'). He finds that white spotting is recessive to self-color in agreement with other 

 work, but that the progeny of two piebald mice may have either more or less white than either 

 parent. He believes that his results can be explained by means of multiple factors without 

 assuming either factor inconstancy or contamination. — Sewall Wright* 



659. Plough, Harold H. Linear arrangement of genes and double crossing over. Proc. 

 Nation. Acad. Sci. [U. S. A.] 5: 167-16S. May, 1919. — Plough has demonstrated that cross- 

 ing over varies with temperature and probably with other environmental factors. Bridges 

 had shown that crossing over varies with age. These influences, very marked for short regions, 

 gradually vanish as distance increases. This must mean that double crossing over is increased 

 proportionally more than single crossing over — which can actually be demonstrated if inter- 

 mediate points are followed, but remains undetected if they are not. On theory of linear 

 linkage, double crossing over is not, as Castle claims, "unproved hypothesis," but absolutely 

 required by evidence. Castle's theory would necessitate assumption that long chromosomal 

 "distances" are less affected by environment than short ones. — Alexander Weinstein. 



660. Rabaud, Etienne. Evolution et sexualite. [Evolution and sexuality.] Scientia 

 25: 275-2S7. 1919.— Problem of sexuality is physico-chemical, not morphological. Sex and 

 sexual reproduction may be influenced by external factors, or by internal features such as 

 chromosomes; action is physiological in either case. Hermaphroditism implies sexuality, 

 may be more recent than separation of sexes, and requires no special explanation. Regarding 

 utility of sexual reproduction, author rejects rejuvenscence theory, including production of 

 favorable recombinations (Jennings). Sees no connection between parasitic or sedentary 

 modes of life and sexuality. Evolution occurred before sexuality existed, hence evolution 

 by recombination can not be any great advantage. Sexuality arose as result of exchanges 

 between living matter and external influences. Species thus becoming sexual continued to 

 live, not because sexuality brought them any advantage, but because it did them no harm. 

 Or, if some species were thereby injured, they perished. — A. Franklin Shull. 



661. Reed, H. S. Growth and variability in Helianthus. Amer. Jour. Bot. 6: 252-271. 

 S fig. June, 1919'— See Bot. Absts. 3, Entries 1028, 1029. 



662. Sage, E. Jtjdson. Variability in plants. Gard. Chron. 65: 308. June 21, 1919. — 

 See Bot. Absts. 3, Entry 1023.] 



663. Schacke, Martha A. A chromosome difference between the sexes of Sphaero- 

 carpostexas. Science 49: 218-219. Feb. 28, 1919.— See Bot. Absts. 3, Entry 1034. 



664. Schmidt, Johs. Racial studies in fishes. II. Experimental investigations with 

 Lebistes reticulatus (Peters) Regan. Jour. Genetics 8: 147-153. 1 graph. June, 1919. — See 

 Bot. Absts. 3, Entry 2191. 



665. Snyder, H. Wheat breeding ideals. Jour. Amer. Soc. Agron. 10: 113-119. 1918. — 

 See Bot. Absts. 3, Entry 2199. 



666. Sttjrtevant, A. H., C. B. Bridges, and T. H. Morgan. The spatial relations of genes. 

 Proc. Nation. Acad. Sci. [U.S. A.] 5: 168-173. May, 1919.— In Castle's three-dimensional 

 diagram [see Bot. Absts. 2, Entry 658] only a few loci lie outside a single plane. These excep- 



