20 MORPHOLOGY AND DEVELOPMENT OF YEASTS 



really quite widespread among the yeasts. Since the discovery of 

 Zyg. Barken, Klocker 1 has recorded the existence of a similar copula- 

 tion in Zyg. Priorianus and Zyg. mandshuricus, de Kruyff 2 in 

 Zyg. javanicus, Saito 3 in Zyg. japonicus, Dombrowski 4 in Zyg. lactis, 

 Takahashi in Zyg. Major, Richter in Zyg. mellis acidi, and Pearse 

 and Barker 5 in a yeast from cider provisionally designated as " Yeast 

 F." Chatton has also described an isogamic copulation in a yeast 

 isolated from Drosophilia funebris which he names Coccidiascus 

 Legeri. 6 It seems that this copulation existed among other yeasts but 



had not received the atten- 

 tion of authors who described 

 them. 



Among all of these yeasts, 

 copulation occurs exactly as 

 in Sch. Porribe and mellacei. 

 It obtains between adjacent 

 cells and very closely related 

 parents. With Zyg. Priori- 

 anus, for example, copulation 

 almost always takes place be- 

 tween two ' cells of the same 

 colony made up of 15 or 20 

 cells. Sometimes it takes place between cells in a colony composed of 

 only 3 or 4 cells. It happens also that one is able to see a cell in the 

 act of forming a bud and also fusing with the latter before it has 

 achieved its full development. In this case, the asc which results is 

 composed of two unequal enlargements; one, the larger, representing 

 the mother cell, and the other representing the bud. The ascospores 

 not having sufficient space for germination into the bud, form them- 

 selves uniquely in the mother cell. In this manner, copulation nor- 

 mally isogamic finds itself heterogamic. Perhaps we may see in this 

 anomaly a tendency to heterogamy. 



1 Klocker, A., in Lafar Handbuch der Technischen Mykologie. G. Fischer, 

 Jena, 1905. 



2 de Kruyff, E. Untersuchungen iiber auf Java einheimische Hefenarten, 

 Cent. Bakt. 21, 1908. 



3 Saito, K. Preliminary notes on the spore formation on the so-called "Soya 

 Kahmhefe." Botanical Mag. 13, 1909. 



4 Dombrowski, W. Die Hefen in Milch und Milchprodukten. Cent. Bakt. 

 Abt. II, 28, 1910. 



6 Pearse, B., and Barker, P. The yeast flora of bottled ciders. Jour. Ag. 

 Sci. 3, 1908. 



6 Guilliermond, A. Quelques remarques sur la copulation des levures. Annales 

 mycologici, 8, 1910. 



Fig. 22. Copulation and Formation of the 

 Asc in Zygosaccharomyces Priorianus. 



