SEXUALITY 



27 



Fig. 30. 



Formation of the Asc in 

 F" of Rose. 



'Yeast 



Guilliermond and was found to present a series of curious character- 

 istics. 1 It forms only a few ascospores and it looks as if its sporogenic 

 function is on the verge of extinction. However, when the yeast 

 is placed in media suitable for spore formation, almost all of the cells 

 put out long projections by means of which they attempt to anas- 

 tomose two by two. Often these do not join together, as if there 

 were an opposing force at work, 

 or as if by a loss of sexual 

 attraction, these projections when 

 they come in contact continue to 

 elongate and thus form a net- 

 work. (Fig. 30.) In quite a 

 number of cases some may estab- 

 lish a union for anastomosis by 

 means of their projections and 

 adhere sufficiently so that a 

 slight pressure does not cause 

 them to break apart. The wall 

 which separates the two cells never quite disappears and in each case 

 fusion does not take place. (Fig. 30, a.) 



Occasionally, the projections from the cells undergo an excessive 

 elongation, since, not having accomplished their function, they form 

 a little bud at their extremity. Often a cell may give forth many 



little projections at different points on its 

 surface in different directions and even 

 these are capable of ramification. In 

 this manner very peculiarly shaped cells 

 are secured which look like amebae. 

 Without much doubt Lindner observed 

 analogous forms in the pellicle of cultures 

 of Saccharomyces Bailii. (Fig. 31.) The 

 forms of copulation, depicted by this 

 author, seem to demonstrate the exist- 

 ence of a copulation in this yeast. The 

 ameboid cells represent, then, unsuccessful copulation. 



Only a certain number of the cells which have just been de- 

 scribed, about 28 per cent, enter the asc stage. All of the others be- 

 come degenerate forms. The ascospores, in the number of from 1 to 

 4, originate in the body of the cell; but they are able to enter the 

 interior of the projection which assumes a bulged form. 



1 Guilliermond, A. Sur la regression de la sexualite dans les levures. Soc. de 

 Biol. 70, 1911. Sur la reproduction de Debaromyces globosus et sur quelques 

 phenomenes de retrogradation de la sexualite" des levures. Comp. Rend. Acad. 

 des Sciences, 151, 1911. 



Fig. 31. Ameboid Forms of S. 

 Bailii in an Old Culture on 

 Nutrient Gelatin. Some of 

 the Forms have Sporulated 

 (after Lindner). 



