9-8 



THE yEAST CELL 



of older asci. When the ascus has ruptured, a spore is gently lifted 

 away from its companions and the dissecting needle lowered clear of 

 of the lower surface of the coverslip. The low power objective is 

 now placed in position and an agar droplet brought within the field. 

 The agar is centered, brought into focus, and the higher power ob- 

 jective replaced. The needle carrying the single spore is gently 

 raised toward the surface of the drop to deposit the spore onto the 

 agar. After deposition, the needle is again lowered and the low 

 power lens is brought into position to locate the approximate site 

 of deposition of the ascus. Using the high dry objective, one returns 

 to the remaining three spores and each of them is deposited on the 

 agar droplets in the same manner. When all four spores have been 

 isolated on agar, the coverslip is removed from the chamber with a 

 pair of sterile forceps and placed (agar downward) over the greased 

 rim of a Van Tieghem cell and incubated at 29°C. imtil microcolonip° 

 of haploid yeast visible to the naked eye appear (fig. 9-6). 



Fig. 9-5 Placing the Coverslip with Hanging Drops on the 

 Moist Chamber. 



Each microcolony, or the agar drop bearing it, is removed from 

 the coverslip under a dissecting microscope with a spatulate inocu- 

 lation needle, and the inoculum streaked over the surface of an agar 

 slant. Each haplophase receives a consecutive number as it is 

 streaked on the slant and the four isolates from a single ascus are 

 held together with an elastic band. 



