152 



ANATOMY OF THE YEAST CELL 



elongation and separation of the nuclear body into two parts. 

 The two nucleoli, which are still connected by a thin thread, 

 then move tow^ards that part of the cell at which the bud 

 commences to protrude. One of them passes into the embryo 

 daughter-cell, and develops into the nucleus thereof, enveloping 

 itself with a membrane — as does also the other which has 

 remained in the parent-cell. A view of the different stages of 

 this subdivision is given in Fig. 150. During sporulation a 

 similar subdivision occurs. Two daughter - nuclei are first 

 formed, which, of course, remain in one and the same cell, and 

 thereby give rise to the exceptional case, referred to above, of 

 more than one nucleus being present in a yeast cell. Both 

 these nucleoli eventually undergo a second svibdivision , the 

 resulting four nuclei then consuming the existing cytoplasm 

 for the purpose of developing into a corresponding number of 



Fig. 150.— Saccliaromyces Ludwigii Hansen. 



Cells at various slas'es of budding. Stained. 



a, Subdivision of nucleus accomplished ; the daughter-nucleus entered into the 

 daughter cell still remains attached to the connecting thread ; 



b, the latter becomes detached ; 



c, the septum between mother and daughter-cells commences to form ; 



rf, the separation is complete. Magn. 1200. (After Janxsemi and Lchlane.) 



ascospores, each enveloped in a new membrane. In the event 

 of eight spores being formed, the process of subdivision must 

 first be repeated. In cells containing a different number of 

 asco.spores {e.g. six or nine), it naturally follows that the process 

 of subdivision has not been repeated the same number of times 

 in all the nuclei, but has ceased in some eai'lier than in others. 

 Finally it may be mentioned that the processes just referred to 

 cannot be distinguished in the living cell without preparation 

 — as-KiiASSER (II.) unsuccessfully endeavoured to accomplish — 

 but that recoiu'se must be had to a suitable method of staining 

 in order to render them visible. 



Since, as already stated, the nucleus in an unstained yeast 

 preparation may readily be mistaken for a vacuole, and vice versa, 

 by an unskilled eye, it is necessary to make a few remarks with 

 i-egard to these vacuoles. As a rule — to which an exception is 

 afforded by e.r/. Sarcharomijces a]>ictdahis — the appearance of 

 one or more vacuoles in the yeast cell is coincident with ex- 

 haustion and with a lack of nourishment. Up to the present no 



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