132 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nucleus, with two pyrenoids, one before and one behind it. At the anterior 

 end is a conspicuous crescent-shaped red " stigma." At the anterior pole 

 are also two vibratile cilia projecting through small tubes in the membrane. 



Vegetative division takes place in the night, the contents dividing first 

 into two and then into four, the pseudopodia being withdrawn. The four 

 daughter-cells then surround themselves each with a delicate cell-wall, and 

 each developes two cilia, the cilia of the original individual still remaining 

 attached to its membrane after the daughter-cells escape from it. The 

 stigma of the original cell occupies a posterior position in one of the 

 daughter-cells, the stigmas not being developed in the others till after 

 their escape. A reversal of the poles and of the direction of movement 

 takes place on each division. 



The formation of microgonidia takes place in the latter part of the day, 

 the first stages of the process being the same as in vegetative division, but 

 the bipartition continues until 32 or 64 distinct bodies are formed, the 

 stigma eventually entirely disappearing. The microgonidia thus formed 

 are about 1/10 the size of the ordinary swarming cells; they are pear- 

 shaped or fusiform with a hyaline anterior and pale green posterior end ; 

 at the former end is an obscure stigma and two cilia ; they have no 

 membrane. Conjugation takes place as soon as they escape from the 

 mother-cell, and microgonidia from the same mother-cell may unite ; 

 they lose their cilia and develope a cell-wall of cellulose. The resulting 

 resting-cell acquires a red colour from the formation of hjematochrome, 

 and remains dormant during the winter ; in the spring the whole con- 

 tents escapes from the membrane, excretes a cell-wall, and developes into 

 a normal swarming cell with two vibratile cilia. 



Spore-formation in Yeast.* — Herr A. Zalewski has investigated spore- 

 formation in Saccharomyces ellipsoideus Eees, S. apiculahis, and Mycoderma 

 villi. After the cells have been left twenty-four hours in water, they cease 

 to be very refringent, and become finely granular. The protoplasm collects 

 on the walls, afterwards shrinks up at one point, and gathers on either 

 side of this. It incloses black points which the author regards as de- 

 veloping nuclei. These, however, soon disappear, and the two masses 

 increase rapidly, rounding themselves off" and forming a membrane. In 

 Mycoderma vini the nuclei are more evident, and the spore-formation 

 again takes place by division of the protoplasm. In the vegetative forms 

 the nuclei can be readily demonstrated by placing the cells in water for 

 some hours, and then treating them with haematoxylin and alum solution. 



Detection of "wild yeast" in low yeast.f — Herren J. C. Holm and 

 S. V. Poulsen have determined by experiment the minimum quantity of 

 " wild yeast" — giving a bitter taste to the wort without causing fermenta- 

 tion — which can be detected in the " low yeast " of Saccharomyces cere- 

 visise. The mode of recognition employed was Hansen's, viz. the formation 

 of ascospores ; and the authors found that even as small an admixture as 

 0-5 per cent, could be detected in this way, the "low forms" used being 

 S. Pastorianus and ellipsoideus. With an admixture of from 1 to 2 per 

 cent, of " wild yeast," ascospores begin to be formed in 30 hours, and are 

 abundant in 40 hours. 



Acetous Fermentation.l — Sig. A. Eomegialli states, as the result of a 

 number of experiments, that the growth of the acetous ferment is increased 



* Arch. Slav, de Biol., ii. (1886) p. 293, from Ann. Acad. Sci. Cracovie, 1885. 

 t Medd. Carlbberg Lab., ii. (188G) pp. 147-.5. See Bot. Centralbl., xxvii. (1886) 

 p. 231. 



+ Gazzetta, xvi. (1886) pp. 73-101. 



