116 



ment maltose but not saccharose, a characteristic unknown for any 

 yeast species described up to that time. 



Beijerinck's removal to academie surroundings made him three 

 years later decide to reinvestigate the species in question i). Useful 

 indications are given for the isolation of the organism : the relatively 

 great thermostability of the ascospores in the dry state making it 

 possible to bring about a separation from other yeast species simultan- 

 eously present on the surface of the dried fruits from subtropical 

 regions (raisins, f igs, dates) . The occurrence of asporogenous strains is 

 dealt with in detail. Much attention is also given to gelatine lique- 

 faction, which phenomenon is especially marked in the stage of spore 

 formation and liberation. It remains surprising that the isogamic copu- 

 lation as an introduction to the formation of the asci has escaped 

 Beijerinck's attention, the more so since in the explanation to the 

 figures he mentions that many of the asci are characterized by their 

 yoke-like shape. 



A paper of considerable methodical and theoretical interest 

 appeared in 1898 2). In this memoir Beijerinck dealt with the diffi- 

 cult question of the loss of spore-forming power which is only too 

 frequently observed in sporogenous yeast species, on continued 

 cultivation in pure culture. Beijerinck found that colonies of 

 Schizos. octosporus which had originated from ascospores always aft er 

 some time formed ascospores again, but that this formation did not 

 occur when the colonies were derived from ordinary vegetative cells. 

 Upon this he based a method for regeneration, or at least for intensifi- 

 cation, of the spore-forming power : cultures in which only rare asco- 

 spores were present were submitted to desiccation and heating at 

 50° C. Under these conditions the vegetative cells were as a rule 

 killed, whilst the few ascospores present withstood this operation, 

 so that on streaking a suspension of the dried material on wort-gela- 

 tine, colonies were obtained which formed spores abundantly. The 

 method was applied successfully to various yeast cultures which had 

 nearly lost their spore-forming power. Several useful indications 

 were also given, which enabled a quick and easy differentiation be- 

 tween spore-forming and non-spore-forming colonies. 



In the light of the present state of our knowledge regarding the life 

 cycle of yeasts, it is noteworthy that Beijerinck should have de- 

 scribed the occurrence in several cases of special strains which differed 

 from the original culture by the much smaller dimensions of their cells. 

 Although no interpretation of this phenomenon was offered, it seems 

 likely that these strains must be considered as haploid forms. Such 

 forms were later described and recognized as haploid by Kruis and 



1) Centralbl. f. Bakt. u. Parasitenk. II, 3, 449 und 518, 1897. 



2) Centralbl. f. Bakt. u. Parasitenk. II, 4, 657, 1898; Arch. néerl. d. sciences exactes 

 et naturelles Sér. II, 2, 269, 1899. 



