No. 2, November, 1920] GENETICS 93 



665. DE Vries, E. Versuche iiber die Frucht- und Samenbildung bei Artkreuzungen in 

 der Gattung Primula. [Study on fruit and seed formation in species crosses of the genus Prim- 

 ula.] Recueil Trav. Bot. Neerland. 16: 63 203. L919. See Bot. Absts. 6, Entry 739. 



666. Dufour, L. [Rev. of : Daniel, L. Les symbiomorphoses ; nouvelles recherches sur 

 l'hybridation asexuelle. (The symbiomorphoses; recent investigations on asexual hybridiza- 

 tion.) Revue brctonne de Botanique pure et appliquee, 1917.] Rev. Gen. Bot. [Paris] 30: 

 367-36S. 1918. — The term "symbiomorphosis" is applied to the diverse modifications of plants 

 verified as the result of grafting. Two cases are distinguished according as the grafts are 

 between different species or upon hybrids. — (1) Grafts between different species of cacti, 

 vines and conifers are mentioned with the peculiar modifications produced. The cabbage 

 when grafted on the tomato exhibited two tomato characters viz., an internal medullary liver 

 and extremely thin crystals of calcium oxalate in the cells. (2) Under symbiomorphoses 

 among hybrids three kinds of effects are described in specific instances viz., returning to the 

 parental types (pears, vines); attenuation or reinforcement of characters (vines); occasional 

 reappearance of ancestral characters (vines). Author's conclusion: "in the same graft one 

 may encounter variations of diverse origin which are blended together or which encroach 

 upon one another. In general, symbiomorphoses are almost always a resultant complex 

 (globale) of numerous physical, chemical and physiological factors." — E. B. Babcock. 



667. East, E. M. Hybridization and evolution. Amer. Nat. 54: 262-264. May- June, 

 1920. — The two species, Nicotiana ruslica and N. paniculala, fall into distinctly different 

 groups of the genus, yet partially fertile hybrids have been obtained by crossing them, the 

 Fi generation being intermediate and as uniform as either parent. Few of the gametes are 

 viable, yet the F2 generation is inordinately variable, which indicates that the two species 

 differ in an extremely large number of inherited factors. The factors for normal fertility re- 

 combine in the Mendelian sense just as do the factors for other characters, so that highly fer- 

 tile strains can be selected some of which are more unlike than the two original species. Eight 

 of these strains were crossed in all possible combinations and every Fi generation exhibited as high 

 a degree of fertility as that shown by the parents. — Lotsy's theory of evolution through hybridi- 

 zation, founded on the study of crosses in Nicotiana, Pisum, Petunia and Antirrhinum, which 

 gave results comparable with the above, was based on assumptions which are open to numerous 

 criticisms. Yet hybridization has played some part in evolution and it is important to 

 determine the limits of its role. Author's observations suggested to him that the F2 genera- 

 tions arising from partially sterile Fi interspecific hybrids might furnish much of the varia- 

 bility required for evolution under domestication, the chief cause of which is shown by both 

 historical and experimental evidence to be hybridization of species. But evolution under 

 domestication must not be confused with natural evolution. The perfect fertility within 

 groups of domestic animals and cultivated plants stands in contrast to the marked sterility 

 between the great majority of natural species. Author's evidence and observations on domes- 

 tic forms yield no indication of a tendency toward production of ' segregates that exhibit 

 either incompatibility in crosses or sterility of hybrid offspring. — E. B. Babcock. 



668. Eriksson, J. Platanthera bifolia X montana i Blekinge. [Platanthera bifolia X 

 montana in Blekinge (Sweden).] Bot. Notiser 1918: 59-62. 1918.— At some few places in 

 Blekinge this hybrid has been found. Its appearance and occurrence are given. The flowers 

 are, as in Platanthera montana, scarcely nice smelling. The fruits nearly always fail to 

 develop. — K. V . Ossian Dahlgren. 



669. Federley, H. Arftlighetsforskningens resultat tillampade pa manniskan. [Results 

 of genetical science applied to mankind.] Studentforeningens Verdandls Sm&skrifter no. 218. 

 47 p. , 22 fig. A. Bonnier : Stockholm, 1918. — A lecture read at a meeting of the Swedish Eugen- 

 ical Society. The following matters are treated : The biometrical school, Mendelism, Mendel- 

 ian characters of man, the cytological basis of heredity, sex and the chromosomes, the 

 sex-limited type of heredity, and the social importance of genetical science. — K. V. Ossian 

 Dahlgren. 



