SEXUALITY 15 



spherical, oval, elongated, triangular, kidney-shaped, or hemispherical. 

 Sometimes they are small and hyaline, with a refractive globule in the 

 center. In Debaryomyces and Nadsonia one finds globular ascospores 

 enveloped in a membrane which is covered with stiff, erect pro- 

 tuberances. (Fig. 13, 5.) In Schwanniomyces occidentalis, the asco- 

 spores are provided with a projection about the cells which divides 

 them into two unequal parts. (Fig. 13, 6.) The ascospores of Schizo- 

 saccharomyces may be ellipsoidal or elongated, and their membrane 

 is impregnated with starchy materials which are stained blue with 

 iodin-potassium iodide solution. Nematospora coryli possesses asco- 

 spores which are long and fusiform; they are provided with long 



O 



*5 



9 10 11 



Fig. 13. Showing the Various Shapes of Ascospores in Yeasts. 



1, Ascospores from S. cerevisiae; 2, Ascospores from Willia anomala; 3, Asco- 

 spores from Z ygosaccharomyces chevalieri; 4, Ascpspores from Willia Sa- 

 turnus; 5, Ascospores from Pichia membranaefaciens; 6, Ascospores from 

 Debar omyces; 7, Ascospores from Schwanniomyces occidentalis; 8, Ascospores 

 from Saccharomyces capsularis; 9, Ascospores from Nematospora coryli; 10, 

 Ascospores from Monospora cuspidata; 11, Ascospores from Coccidiascus Legeri. 



structures at their extremities which are similar to cilia. Monospora 

 cuspidata also has long cells which look much like needles. (Fig. 

 13, 9.) 



Most of the yeasts known possess only a single membrane. In 

 S. guttulatus, there are, on the contrary, two membranes. The 

 outer one breaks at the moment of germination. 



SEXUALITY 



(A) Copulation Preceding the Formation of the Asc 



Recent investigations have shown that with a certain number of 

 yeasts, the asc results from a copulation which closely resembles that 

 of cells which one finds in certain of the lower Ascomyces. (Eremascus 

 and Endomyces.) 



It was among the Schizosaccharomycetes that this phenomenon 

 was noticed for the first time. In this group of yeasts, characterized 

 as we have seen by a special multiplication of cells which occurs 

 always by transverse partition, only a few species are known (Sch. 

 octosporus, Sch. Pombe, and Sch. mellacei). These three species show 

 sexual processes. 



