114 GENETICS [BoT. Absts., Vol. IX, 



considering the former proven, the latter perhaps possible in some organisms. "Mutual 

 relations of chromosomes" in syndesis are discussed, it being considered probable that homol- 

 ogous chromosomes fuse at this time. Syngamy, gonomery, and fragmentation of chromo- 

 somes are discussed; also parthenogenesis — facultative and obligatory, haploid and diploid. 

 Cases are cited of diploid parthenogenesis with 2 maturation divisions {Nematus, Rhodites). 

 Sex chromosomes in insects are considered in detail and compared with those of other animals. 

 Special life histories are described; alternation of parthenogenetic and sexual generations 

 are considered with reference to chromosome behavior. E,elation between sex chromosomes 

 and sex determination are briefly considered with the conclusion that in every individual 

 "both sexes must be considered as potential," but in most cases sex chromosomes are "over- 

 whelmingly the most important immediate factor in sex determination." In rare cases, 

 "other factors may be more powerful." Actual influence of sex chromosomes in determining 

 sex is unknown, but the result is probably not due to differences in the mass (amount) of chro- 

 matin. Sex is probably due to hereditary factors residing in the chromosomes. Evidence for 

 genetic continuity of chromosomes is reviewed and the principle is accepted. Homology of 

 chromosomes is discussed. Possible modes of evolution of chromosomes are considered, 

 i.e., fractionation, fusion, tetraploidy, etc. The author reviews evidence indicating that 

 chromosomes are the main vehicles by which ' 'hereditary qualities are transmitted from parent 

 to offspring," and that they initiate and control activities of cell and morphogenesis. A 

 discussion of chromosomal behavior in hybrids is included; also a brief treatment of crossing 

 over and mutation phenomena including somatic mutations. Morphogenesis is immediately 

 affected by "organ-forming substances" of cytoplasmic nature, but is ultimately controlled 

 by the nucleus. Chromidia are considered, with the conclusion that their origin is in doubt 

 and their function not clear. Chondriosomes, which may be identical with chromidia, are 

 likewise of doubtful origin; there is practically no evidence that they reproduce regularly 

 by fission or that they are equally and regularly distributed in cell division. They are proba- 

 bly not the seat of morphogenetic factors, and are not, on the basis of present knowledge, to 

 be considered as idioplasmic. The final chapter is devoted to nuclei of Protista and plants. 

 Chromatin-cytoplasm differentiation may be lacking in some bacteria. "Modes of nuclear 

 multiplication in the Protista are of bewildering varietj^" Recent evidence renders sup- 

 posed cases of amitosis in Protista doubtful. Likewise the supposed non-qualitative divisions 

 of chromatin by means of chromidia are somewhat doubtful. Polyploid nuclei occur in cer- 

 tain stages of some Protista; e.g., the radiolarian Aulacantha has one chromosome in some 

 nuclei, over 1,000 in others; both types apparently carry a full set of hereditary factors. 

 Meiotic phenomena in plants are essentially similar to those in' animals. Differences 

 between animals and plants are discussed, especially variations in prominence of hap- 

 loid (gametophyte) generation in plants. [See also Bot. Absts. 7, Entry 850.] — C. W. Metz. 



732. Alverdes, Friedrich. Zum Begriff der Scheinvererbung. [The concept of false 

 heredity.] Zeitschr. Indukt. Abstamm.- u. Vererb. 25: 164-169. 3 fig. 1921.— The term 

 "false heredity" is applied to a change produced in a line of descent by changed surroundings, 

 which change remains for as many generations as the change in the surroundings persists 

 so that the line of organisms comes back to normal only when, or a few generations after, 

 the surroundings again become normal. Thus, non-heritable changes are classed as changes 

 in the environment, and heritable changes as changes of the genotype. The problem of inheri- 

 tance of acquired characters therefore becomes the problem of changes in the genotype pro- 

 duced by changes in the surroundings. — John Belling. 



733. Bannier, J. P. [Dutch rev. of: Allen, E. J., and E. W. Sexton. Eye-colour in 

 Gammarus. Jour. Genetics 9: 347-366. 1 pi., 1 diagram. 1920 (see Bot. Absts. 7, Entry 

 840).] Genetica3: 63-64. 1921. 



734. Bannier, J. P. [Dutch rev. of: Jones, D. F. Selective fertilization in pollen 

 mixtures. Biol. Bull. [Woods Hole] 38:251-289. 1920 (see Bot. Absts. 6, Entry 1699).] 

 Genetica 3: 68-70. 1921. 



