ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 207 



and on the systematic position of the closely allied Saccharornycetes. 

 He finds that the formation of the spores in Eremascus is exactly com- 

 parable with the same process in Saccharomyces, and that the ascus of 

 the one is homologous with that of the other. In Endomyces fibidiger 

 there are variations from these forms, though they are closely allied : 

 there are only four spores formed in the ascus instead of eight, and 

 there is no trace of sexual conjugation. Saccharomyces capsidaris, 

 another closely allied form, differs in the total absence of any anastomosis 

 of hyphas, which is a feature of Endomyces fibuliger. He finds, how- 

 ever, in E. magnusii a true heterogamic conjugation representing sexual 

 reproduction. It is also characterised by a much-branched mycelium. 



Guilliermond describes at great length the development of these 

 different fungi, compares them one with another, and discusses the views 

 on their systematic positions held by various authors. He finds little 

 difference between Endomyces fibidiger and Saccharomyces capsidaris, 

 and places them in the same genus ; he show T s further their affinity with 

 Eremascus. The latter should include forms characterised by the 

 absence of conidia, and an H-spored ascus derived from an isogamic con- 

 jugation. Guilliermond's study of these various types leads him to 

 conclude that the yeasts are derived from a form akin to Eremascus 

 fertiJis. From that original form he traces two lines, the one including 

 Endomyces fibuliger, E. capsidaris, Zy go saccharomyces, and the Saccharo- 

 mycetes, the other Endomyces magnusii and the Schizosaccharomycetes. 



Cytological Observations on the Yeast Plant.*— H. Wager and 

 A. Peniston refer to a previous paper published by Wager on the yeast- 

 cell nucleus in which he stated that the combined nucleolus and vacuole 

 constituted the nucleus of the cell. They give the views of other 

 workers who contest this statement, and describe their methods of 

 culture, fixing, and staining employed to enable them to make a new 

 examination of the subject. They conclude again, as a result of their 

 work, that the nucleus consists of nucleolus and vacuole ; the vacuole 

 contains a clear nuclear sap, a network of strands which occur mainly at 

 the periphery, and one or two bright metachromatin (volutin) granules. 

 The nucleolus always occupies a position at the side of the vacuole and 

 projects into the cytoplasm of the cell. There is no well marked 

 nuclear membrane. The nuclear vacuole varies in size and seems to 

 disappear entirely during spore-formation. The nucleolus and the net- 

 work of the vacuole may become impregnated with chromatin, and these 

 give a distinct reaction for phosphorus and iron. The cytoplasm 

 contains bright volutin granules, and glycogen is abundant at certain 

 stages. 



In the process of bud-formation the nucleus divides amitotically into 

 two equal or unequal portions, one of which passes into the daughter- 

 cell with a portion of the vacuole and chromatin. In spore-formation 

 the nuclear vacuole and network disappear, the nucleolus becomes closely 

 surrounded by chromatin granules and then divides by elongation and 

 constriction ; the two daughter-nuclei divide in a similar manner to 

 form the spore-nuclei. 



* Ann. Bot., xxiv. (1910) pp. 45-83 (5 pis.). 



