78 GENETICS [Bot. Absts., Vol. IV, 



strable suspicion of hereditary degeneration is justified. A clinical classification is pro- 

 posed for the better known hereditary forms of cerebral degeneration, but at the same time 

 it is pointed out that the student of these conditions does not deal with sharply defined entities, 

 since it is quite unusual, except among relatives, to find two cases that agree in all respects. — 

 C. H. Danforth. 



522. Blakeslee, A. F. Plant genetics. [Rev. of: Coulter, John M., and Merle C. 

 Coulter. Plant genetics. 13 X 19 cm., ix + 214 P-, 40 fig. Univ. Chicago Press: Chicago, 

 July, 1918.] Plant World 22: 181-182. June, 1919— See Bot. Absts. 2, Entry 395. 



523. Blaringhem, L. Les problemes de Pheredite experimentale. [The problems of 

 experimental heredity.] 12 X 19 cm., 817 pages, 20 fig. 1919.— Author presents various kinds 

 of facts of heredity and offers classification of them; he intentionally omits characters re- 

 cently acquired and not yet fixed, and also mutational phenomena; he takes special account of 

 work of French hybridizers of the 19th century whom he thinks modern geneticists have 

 neglected. The work is divided into three sections, dealing respectively with "normal hered- 

 ity," species hybridization, and varietal crossings. — Section 1. After general discussion of the 

 meaning of purity among living things author defines "pure line" giving it not only a genea- 

 logical concept but also one in which no divergent individuals may be included. Advan- 

 tages of barleys for pure-line studies are emphasized. Hereditary phenomena to be ob- 

 served when individuals of the same pure line are parents is named normal heredity and proofs 

 of transmission of qualities of ascendants to descendants is here so evident that their inves- 

 tigation offers little attraction. If qualities of parents deviate from the mean of the line, 

 progeny are expected to show regression and there arises what the author names "fluctuating 

 heredity;" this occurs with continuous characters and is studied by biometrical methods. 

 A sympathetic presentation of laws and formulae of regression, ancestral inheritance and of 

 father-son correlation is given. Author regrets application of biometrical methods to discon- 

 tinuous characters, as eye color, and points out that Mendelian heredity has given better 

 account ; he also deems it premature to apply them to psychological traits. — Section 2. Author 

 asserts his belief in genetically permanent blends following on some hybridizations and takes 

 exception to the idea of multiple factors with segregation. Examples of blending (herSdite 

 mixte) often occur in crossings of species, even elementary species, where more or less ster- 

 ility occurs in first generation. Mendel's laws are thought not to hold in these cases. Author 

 conceives of combination in chemical sense, of certain cell elements, followed by expurgation 

 or refining which leads to stabilization and increased fertility. He believes this process 

 explains in part the diversity of species and genera. He gives the origin of Aegilops speltae- 

 formis as a case of such permanent blend resulting from crossing of wheat and Aegilops ovata. 

 Other cases cited are skin color in human beings, rabbit-hare hybrids, and Cavia species 

 crosses. — This section treats also of "mosaic heredity," whose characteristics were set forth 

 by Naudin about 1859 (hence also designated Naudinian heredity) on the basis of results of 

 crossing Datura stramonium and D. laevis, former with spiny and latter with smooth capsules. 

 Three of the 40 Fi hybrids bore "composite" capsules [chimaeras], partly spiny and partly 

 smooth, the extent of smoothness being greatest in the youngest capsules. These were inter- 

 preted by Naudin as the disengaging of two species forcibly united. Author's own work on 

 barleys is cited in support of the existence of mosaic heredity; 14 of 17 hybrids of a certain 

 cross uniformly exhibited spiny-nerved glumes, the remaining 3 exhibited mosaic behavior 

 with individual heads bearing spiny, spineless and intermediate condition, with spineless 

 glumes typically more frequent a1 hase and tip of heads. The progeny of such smooth-glumed 

 grains may not show smoothness again and spiny grains did not always give offspring uniformly 

 spiny; this leads author to suppose independence between traits separated out (dissocics) on 

 glumes and character of embryos enclosed hy the glumes. The appearance of such mosaics 

 is considered an indication of profound difference between lines united by hybridization. 

 This somatic separation of characters occurs without precise rules but tends to show at 

 extremities of the axes or in late buds. Section 2 discusses lastly "unilateral heredity." 



eies of Fragaria are cited as more or less subject to unilateral transmission. Author 



