ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 599 



Pseudo-vacuoles of Yeast-cells and Development of Pseudo-cell 

 nuclei.* — There have been many views as to the nature of the con- 

 tents of the yeast-cell ; J. J. van Hest has made a new series of 

 researches, and presents new conclusions. He finds that the bodies 

 considered to be nuclei in yeast-cells are only pseudo-nuclei, because 

 they are already young yeast-cells ; that the young cell-nuclei, when 

 already independent, are ultramicroscopic ; that the cells already formed 

 are expelled from the mother-cell and do not arise by budding ; and 

 that the pseudo-vacuoles can be induced by starvation, in the course of 

 which the cell-contents eventually disappear, evidently assimilated by the 

 nucleus. As in favourable conditions the yeast-cells are round or 

 ■oval, so, in less favourable, they are elongate and filamentous ; these 

 abnormal forms being rendered necessary in the search for food. He 

 finds that the young nucleus possesses a membrane ; when it stretches, 

 a second is formed, and then a third. The earliest form of the nucleus 

 is not demonstrated ; it must be excessively minute, as the young cell 

 which he names primary cell is also extremely small. When this 

 primary cell is large enough to be seen by the ordinary powers of the 

 Microscope, it is already a secondary cell, and gives rise to primary 

 cells. Thus, the yeast-cell itself is not the place where the " earliest " 

 nuclei appear : they arise in the cell within the yeast-cell. The cells 

 that the " secondary " throws out escape through the outer wall of the 

 yeast-cell, and grow into yeast-cells. In this fully grown, fully developed 

 yeast-cell, he finds that the three membranes of the nucleus are still 

 there ; the outer membrane has become the wall of the yeast-cell, the 

 secondary incloses the secondary cell, the third membrane the primary 

 cell. Finally, van Hest finds that pseudo-vacuoles have no existence : 

 they are an optical illusion. 



Wildier's Bios.f — Pure yeast-cells increase and give rise to fermen- 

 tation only in the presence of a certain organic substance termed Wildier's 

 Bios. M. Ide has made a series of experiments to determine the 

 nature of the " bios." He finds that it is a comrade of cholin, and is 

 widely dispersed, as it comes from lecithin fats. A discussion follows on 

 the advantage or necessity of the presence of bios, etc., and results are 

 given of various experiments. Finally, as a further test, the isolation of 

 biosin is to be attempted. 



Uredine3B|.— E. W. D.. Holway has just issued the part of the "North 

 American Uredinea3 " dealing with Puccinia. He records and describes 

 forms on 15 different natural orders of plants. Holway has not adopted 

 Arthur's nomenclature, though he records his names among the synonyms. 

 The paper is illustrated by reproductions of microphotographs of the 

 teleutospores. 



W. A. Kellerman § publishes a decade of the Fungi selecti Guate- 

 malmsis, all of them species of the Uredineai ; some of them are on new 

 ihosts, others are new species recently described. 



* Centralbl. Bakt. xviii. (1907) pp. 767-87 (3 pis.). 



t Tom. cit., pp. 193-9. 



t North American Uredinese, i. part 3, Minneapolis, 1907, pp. 57-80 (13 pis). 



§ Journ. MycoL, siii. (1907) pp. 99-102, 



