No. 3, December 1920] GENETICS 161 



coat, independent from the other possibly present factors; (2) G, factor for yellowish-brown 

 color; chamois is, if G is present, changed into yellowish-brown; (3) L, factor for liver-brown, 

 by which yellowish-brown is changed into liver-brown, or in bomozygotes dark-brown; (4) 

 V, factor that changes chamois into violet and yellowish-brown into brown-violet. The fac- 

 tor L is epistatic to V, the presence of V thus being indistinguishable when the formula is 

 LI or LL; (5) Gr, factor for gray color, changing chamois into gra3 r -chamois, yellowish- 

 brown into gray-yellowbrown and violet into gray-violet. (6) B, factor changing violet 

 into blue. This factor covers all other factors and is thus epistatic to them; (8) S, striping 

 factor, by which blue, violet and gray in the superficial layers are restricted into stripes. 

 Then one sees a background of chamois, yellowish-brown, liver-brown, gray-violet or bluish- 

 brown. If this background is violet or gray, then S exercises also its influence upon it and 

 makes this violet, marbled; in consequence these beans show two types of markings, viz., 

 striping and marbling. The other colors are not marbled in the background. This factor 

 S may be present in cryptomeric state in the chamois, yellowish-brown and liver-brown colors, 

 but cannot be proven here, because it does not influence these colors. — Probably there are 

 also linkages between some of these factors; perhaps between P, V and S on the one hand 

 and between G, L, B and S on the other. This is the more striking because the formulae 

 derived from the splitting-numbers are for the mother-plant, the dwarf speckled cranberry 

 bean, PPVVSS, and for the unknown father-plant, that must have had white seedcoats, 

 ppGGGrGrvvLLBBss.—M. J. Sirks. 



1122. Sirks, M. J. De methodiek der erfelijkheidsleer. [The methodism of genetics.] 

 Tijdschr. voor diergeneeskunde. 47: 207-217. 1920. — Progress of genetics can only be obtained 

 if a critical examination of the methods in use has preceded the work itself. The critique 

 of the methods in use cannot be sharp enough; in modern times we are no longer contented 

 with the primitive and ancient method of speculation without facts. These facts may be 

 gained by two different ways: direct research of the genetical factors, present in a cell, by 

 cytological studies, and by indirect researches in judging the hereditary factors of an individ- 

 ual by observations or experiments thereupon. This direct method, the cytology, may give 

 us many results, but has thus far not solved the great problem of the localization of heritable 

 factors. In itself cytology is insufficient. Indirect methods of genetics there are four; we 

 may study the chain, that binds the heritable factors in the genotype with the observed char- 

 acteristics of the individual in its phenotypes in two directions: beginning with the genotype 

 as Schaxel does and studying the development of this genotype into the phenotype by cyto- 

 morphological methods or studying by going back from the phenotype-characters and trying 

 to find out the genotypical factors causing them (Phenogenetica Haeckers). — In the second 

 place indirect study of genotype may be drawn along other lines: study of ascendance (Gal- 

 ton) and study of descendance (Mendel). In far the most cases only the last of these methods 

 is sufficient; the methods of Schaxel and of Haecker however may perhaps give us still 

 many results in elucidating the long way between genotypic factors and phenotypic 

 characters. — M. J. Sirks. 



1123. Sirks, M. J. Erfelijkheids- en selectieonderzoekingen bij Vicia-soorten. I. De 

 navelkleur van Vicia Faba. [Researches on heredity and selection in species of Vicia. I. 

 Navel color in Vicia Faba.] Genetica 2: 193-199. 1920.— The navel color in the English bean 

 (Vicia Faba) was studied as a heritable character by breeding the posterities of individual 

 plants; partly these plants were isolated, partly they were allowed to flower without isola- 

 tion. From isolated heterozygous plants splitting offspring in ratio 3 : 1 were always obtained; 

 black navel-color was dominant and white recessive. The heterozygotes could in some cases 

 be distinguished from the homozygotes because of their not black, more gray navel color. 

 Free-flowering plants never gave a more or less exact ratio 3:1; their offspring split in every 

 possible ratio; even in the offspring of white-navel recessives often a great number of black- 

 navel plants could be observed, the results of spontaneous hybridizations. — M. J. Sirks. 



1124. Sirks, M. J., and J. Bijhouwer. Onderzoekingen over de eenheid der linneaan- 

 sche soort Chrysanthemum leucanthemum L. [Investigations on the homogeneity of the 



