SPORE-FORMATION IN SACCHAROMYCETES. 
B. TI. P. Barker, M.A., Gonville and Caius College, 
Camobrid ge. 
In 1883 Hansen (1) published the results of his experiments 
on the conditions necessary for the formation of spores in the 
Saccharomycetes. They were as follows:— 
1. The cells must be placed on a moist surface and have a 
plentiful supply of air. 
2. Only young, vigorous cells can exercise this function. 
3. The formation only proceeds between certain tempera- 
ture limits, the limits varying for different species. 
The most favourable temperature for most species is 
about 25° C. 
Previously little was known concerning the necessary condi- 
tions, and since that time Hansen’s results have been generally 
accepted, until last year, when Klebs (2) suggested that the real 
condition had been overlooked by Hansen, viz.:—The want of 
food, or, to put it more particularly, the sudden change from 
very favourable nutritive conditions to a state, more or less, of 
starvation. Recently another element has also entered into 
the question. Three species, viz. :—Saccharomyces octos porus, 
S. Pombe, and Zy gosaccharomyces—require a process of conjuga- 
tion and nuclear fusion before spores are formed, with the ex- 
ception of a few isolated cases in S. octosporus. Janssens and 
Leblanc (3), in their work on the yeast nucleus also have stated 
that S. cereviszae and other allied species require nuclear fusion 
before fertile spores can be produced. 
The following experiments have been undertaken with a view 
of testing these statements, and can be divided into two groups, 
V1Z. : — 
I. Those in which the effect of external conditions is 
studied. 
II. Those dealing with the conditions of the cells them- 
selves, 2.e., internal conditions. 
I. In all the following experiments, except where otherwise 
stated, the method of testing the capability of the cells to form 
spores under any given set of conditions consisted in pouring a 
few drops of beer-wort, containing actively-growing yeast cells 
upon a square block of Plaster of Paris, about an inch thick, 
contained in a covered glass dish. This was moistened with 
distilled water and placed at 25° C. The yeast cells were 
obtained in an active condition by infecting a tube of beer-wort, 
