: 



( 



igo-j] CURRENT LITERATURE 155 



this may be due to the fact that they have become parthenogenetic. The con- 

 jugation observed in Saccharornycodes Ludmgii by Guilliekmond, where the 

 t endospores conjugate before germination, may be only a secondary development 



introduced into parthenogenetic forms as a means of recuperation. ''The exist- 

 ence of the conjugation preceding sporulation, coupled with the cytological char- 

 acter of the sporange, demonstrate in an evident manner the ascogenous nature 

 of this organ, and one ought to consider with Hansen that the Saccharomyces con- 

 stitute an autonomous group belonging to the Ascomycetes and near to the 

 Exoascaceae.'* — B. F. Lutman. 



Heredity in microHjrganisms. — Working with the yeast Saccharomyces anomaJus 

 and the bacteria 5. coli-commtinisj B, typhosus, and B. megatherium^ Barber'^ 

 has extended the investigations of Hanson, Beijerinck, Conn, Mayer, and 

 others on such variation as may arise spontaneously from cells which vary inde- 

 pendently of environment. The cells chosen were those showing a morphological 

 difference from the parent, and the new races of descendants were tested further 

 for biochemical differences. The problem of isolation was thus a much more 

 difficult one than that of selection of bacterial "sports" in mass with physiological 

 differences, such as that of a white colony among red pigmented oxiq^. Barber 

 devised and describes an ingenious method for isolating single varying cells 

 from a hanging drop under the microscope by means of a capillary tube, with 

 apparatus for holding and adjusting it under the lens. A single, cell drawn into 

 this could be discharged into another hanging drop, placed in a sealed moist 

 chamber, and its development and descendants watched for as many generations 

 as necessary- With the yeast Barber obtained in this way new races whose 

 morphological characters (large, long cells) persisted over three years, such a new. 

 race successfully competing with the parent stock when mixed with it in culture. 

 Attempts to further modify the race by selection failed. Much the same results 

 were obtained with the bacteria. These varieties were true mutations, appearing 

 suddenly wdth full-fledged characters, apparently independent of natural selection 

 and comparable wdth sports among multicellular organisms. If physiological 

 characters are correlated w^ith morphological, as in the case of increased pr)wer of 

 fermentation of one of Barber's races of B. coli, it seems probable that mutation 

 may be a factor in the ori^n of increased virulence of some pathogenic bacteria, — 



Mary Hefferan. 



Position of the nucleus.-- -Kuster^-' has made a rather extensive series of 

 observations upon the relation between the position of the nucleus and cell growth 

 and the formation of membranes. His conclusions differ from those of Haber- 

 landt, especially in reference to the position of the nucleus in root hairs and 

 stomatal apparatus, and in cells undergoing local thickenings of the cell wall. 



12 Barber, Marshall A., On heredity in certain micro-organisms. Kansas 

 Univ. Sci. Bull. 4:3-48. pis, z--/. 1907. 



13 Kt;sTER, Erxst, Ueber die Be^iehungen der Lage der Zellkcmcs zw Zellcn- 

 wachstum und Membranbildung, Flora 97:1-23. 1907. 



