50 CYTOLOGY OF YEASTS 



maturation and serve them as food. At this stage, which corresponds 

 to the beginning of nuclear division, some important modifications 

 appear in the alveoli which contain metachromatic corpuscles. These 

 bodies, increased in number and diminished in volume, undergo a sort 

 of pulverization which reduces them to infinitely small particles 

 which, in their turn, dissolve, the alveoli taking the same color 

 that pertained to the corpuscles. This phenomenon of dissolution 

 of the metachromatic granules is followed by the formation of the 

 ascospores. 



During this time the nucleus undergoes its first division; but, 

 the very chromophile cytoplasm, filled with basophile grains which 



surround it, does not allow the divi- 

 s * on ^ ^ e followed nor any knowl- 

 f (1 ec te e w ^h re S ar d to how it operates. 



nuclei closely related to each other 

 and situated in a zone of sporogenic 

 plasma, which advance by steps to 

 a single large nucleus. However, 



Fig. 51. Formation of Ascospores in cer tain aspects of the phenomenon 

 o. Ludwigii. . 



seem to indicate that the nucleus 



divides by karyokinesis. This has been put in evidence for Schizo- 

 saccharomyces octosporus. 



The two daughter nuclei soon emigrate to both poles of the cell. 

 They are followed by the sporogenic plasma which divides between 

 the two poles in order to surround the nuclei. At this moment, 

 one may observe the steps in which there are two nuclei at each 

 end of the cell surrounded by a zone of sporoplasm and separated by 

 a portion of the same material. Some authors (Janssens and Le- 

 blahc) have attributed this to sort of karyokinetic structures, re- 

 garding the two nuclei surrounded by sporoplasm as the anaphase 

 plates and the thread plasma which unites them as an achromatic 

 spindle. 



Soon the thread which unites the two masses of protoplasm dis- 

 appears and each nucleus undergoes a division. We have seen, 

 then, the stages in which two .small nuclei are placed one at each 

 pole of the cell with a mass of sporoplasm about each. (Figs. 47, 

 7, and 51.) The sporoplasm concentrates about each and forms 4 

 little balls provided with a nucleus and placed in pairs at each pole. 

 These are the ascospores. These increase in size and form a mem- 

 brane about them. At this moment the epiplasm becomes disor- 

 ganized and is reduced to an alveolar fluid containing fats, glycogen 

 and metachromatic corpuscles. The metachromatic granules slowly 



