56 GENETICS [Bot. Absts., Vol. V, 



418. Meader, Percy D. Variation in the diphtheria group. Jour. Infect. Diseases 24: 

 145-157. 1919. — Author's material consisted of 25 different strains of the diphtheria bacillus, 

 isolated, for the most part, from throats of persons infected with diphtheria during epidemic 

 of the disease. Pure cultures were made of each strain by repeated plating on agar. From 

 each pure culture a series of subcultures were made by plating dilutions so prepared that as 

 far as possible each colony represented the progeny of a single organism. Repeated subcul- 

 tures were made from selected colonies of each strain. Progeny of the various colonies were 

 examined in 20 hour slant cultures on Loeffler's serum stained with LoefHer's methylene blue. 

 The frequency of the various Wesbrook types of morphology were tabulated for the original 

 type of each strain and for the progeny of each type. Employing as a criterion of variability 

 in type the fact that the predominating types of morphology present in subcultures were dif- 

 ferent from those present in the original culture, the author found that of his 25 strains 8 

 showed morphologic variation, 4 may have varied only slightly, if at all, and 13 showed no 

 reasonable indication of variation. — -To determine fermentative variability, each of the 25 

 strains were compared with their descendants after the 5th and 10th platings as regards their 

 power to produce acid in dextrose, lactose, maltose, dextrin, and saccharose. More than half 

 of the cultures investigated varied after successive platings as regards their power to produce 

 acid in carbohydrates. — Variability of virulence of the 25 strains was tested by means of the 

 inoculation into guinea pigs of each original type and of its progeny after the 5th and 10th plat- 

 ings. Some strains gained virulence, some lost it and some remained constant in the course 

 of successive platings. Variations in virulence were only in part correlated with morphologic 

 types. Cultures containing granular forms were frequently non-virulent, while those which 

 consisted of solid-staining forms for the greater part of their cultivation were consistently 

 non-virulent. — From a biometric study of the fermentative reactions of members of the diph- 

 theria group it appears that they constitute a genetically related group of organisms. In 

 subcultures derived from one parent strain variations in morphology, in fermentative reac- 

 tions and in virulence, occur, but the virulence of a strain is not correlated with its fermenta- 

 tive reactions nor closely correlated with its morphology. — M. A. Barber. 



419. Metjnissier, A. De quelques idees sur la selection des legumes. [Some ideas on 

 the selection of vegetables.] Rev. Hortic. 91: 300-303. June, 1919.— See Bot. Absts. 5, 

 Entry 1855. 



420. Meves, G. Eine neue Stiitze fur die Plastosomen theorie der Vererbung. [A new 

 support for the plastosome theory of heredity.] Anat. Anzeig. 50: 1918. 



421. Molz, C. Natiirliche und kiinstliche Auslese zur Erzielung widerstandsfahiger 

 Sorten. [Natural and artificial selection for the achievement of resistant varieties.] Deutsch. 

 Landw. Presse 1918: 19. 1918. 



422. Morgan, Thomas Hunt. The physical basis of heredity. 14x21 cm., 300 p., 117 

 fig. J. B. Lippincott Co. : Philadelphia, 1919. — A presentation of the modern factorial theory 

 of heredity, comprising the phenomena of segregation, independent assortment, linkage and 

 crossing over, the linear arrangement of the genes, interference, and the limitation of the 

 linkage groups. Both the genetic evidence and the cytological are presented, and it is shown 

 how the genetic phenomena are explained by the chromosome mechanism. On the basis of 

 these principles an analysis is given of sex and sex-linked inheritance, non-disjunction, par- 

 thenogenesis and pure lines, cytoplasmic and maternal inheritance. There is a discussion of 

 variation in linkage caused by hereditary factors and by environmental conditions. The 

 chapter on "Variation in the number of the chromosomes and its relation to the totality of the 

 genes" deals with triploidy and tetraploidy, and recent work indicating deficiency, dupli- 

 cation of factors in a chromosome, and transposition of factors from one chromosome to an- 

 other. The chapter on mutation includes the explanation of pseudo-mutations by balanced 

 lethals. In "The particulate theory of heredity and the nature of the gene" the author dis- 

 cusses the relation of the genetic factor or gene to somatic characters and to ontogeny. — 

 Alexander Wcinslci/i. 



