No. 2, March, 19211 GENETICS 137 



propagated by continued inoculation for 40 implant-generations, during seven years.— 

 675 mice were used, of two kinds, common domestic mice of European strains, and animals 

 which had one European parent and one Fi, European X Japanese, parent. It had been 

 found previously that the susceptibility to the transplanted tumor of the Japanese parent 

 was completely dominant in the Fi. Genetic analysis of the genes responsible for this dif- 

 ference in susceptibility will be published later. Author states presence of several factors 

 necessary to produce susceptibility. Among animals of the Fi X European class there is 

 therefore great genotypic diversity. In this paper the whole Fi X European class is treated 

 statistically and its susceptibility compared to the pure European class. In this latter class 

 11.12 per cent of the observations made showed positive tumor-growth, in the Fi X European 

 class, 17.54 per cent of the observations were positive. In this class there was found a dis- 

 tinct difference in tolerance for tumor-growth between younger and older mice of female 

 sex. Certain factors of the Japanese genotype must in some cases, even when separated, 

 exert a favorable influence upon temporary growth of tumor. The Japanese strain, which 

 was found to possess twelve to fourteen independent genes absent from European mice and 

 favoring growth of a different tumor if present in combination was found to be remarkably 

 pure. (The Japanese waltzer is a variety of the common Oriental domestic mouse, which is 

 zoologically quite different from MurS mtisculus and is probably derived from Mus wagneri 

 Ret.) — A. L. Hagedoorn. 



912. Llotd-Jones, O., and J. M. Evvard. Studies on color in swine. I. The heredi- 

 tary relationship of the black of the Hampshire and the red of the Duroc-Jersey. Iowa Agric. 

 Sta. Res. Bull. 53: 203-208. 1919.— Authors point out that while the white of Yorkshires or 

 Chester-Whites is completely dominant to the black of Berkshires or Poland-Chinas, a blue 

 roan generally with a white belt results when a Hampshire (black with white belt) is crossed 

 with a Chester-White. They also point out that while the Berkshires or Poland-Chin as crossed 

 with red breeds (Duroc-Jerseys or Tamworths) give red animals with black patches, black 

 animals sometimes having white belts are produced when Hampshires are crossed with 

 Duroc-Jerseys. Evidence is also given to prove that in the last-mentioned cross black is a 

 simple dominant. — H. L. Ibsen. 



913. MacCubdt, H. M. Division, nuclear reorganization and conjugation in Arcella vul- 

 garis. Michigan Acad. Sci. Ann. Rept. 21:111-113. 1919.— The number of daughter cells 

 produced by a single individual is limited, and varies from none to twenty-seven. The mem- 

 bers of a pair of ex-conjugants tend to produce the same number of daughter cells at about 

 the same rate. In lines derived from a single individual, "depression" periods and conjuga- 

 tion occur at intervals of from four to six weeks; while some members of a line are depressed, 

 others undergo conjugation. Individuals may pass successfully through a period of depres- 

 sion and enter upon a new period of division. Preparations of cells made during the time of 

 depression show the vegetative nuclei inactive or breaking up, and "secondary" nuclei form- 

 ing from part of the chromidial net. Preparations of conjugating individuals show remark- 

 ably similar conditions. In many cases, the secondary nuclei have been observed to enter 

 daughter cells, while the old vegetative nuclei remain in the old shell. If the nuclei consti- 

 tute the germ-plasm, its continuity is interrupted at the time the old vegetative nuclei cease 

 to divide and begin to disintegrate, and the secondary nuclei are organized from the chromidial 

 net and pass into the daughter cells. If chromidiogamy occurs at the time of conjugation, 

 as is maintained, nuclear continuity is still interrupted, and is only secured in the process of 

 construction of new nuclei out of the chromidial net. There is thus a discontinuity of nuclei 

 with a nuclear cycle of development. If the nuclei are successively similar at corresponding 

 stages, the lines run true; if not, variations due to their dissimilarities are produced.- 

 Bertram G. Smith. 



914. Macoun, W. T., and M. B. Davis. Progress in apple breeding for the Canadian 

 prairies. Proc. Amer. Soc. Hort. Sci. 1919: 13-18. 1919.— The Canadian prairies are situ- 

 ated between 49° and 53° north latitude and between 97° and 114° west longitude. Altitudes 

 range from 700 feet to 4200 feet. Spring is early; buds swell in April. Summers are rela- 



