
144 
yeast-form and the chlamydospore-form belong to the same fungus, by 
the separation and culture of a single yeast-cell. This was done by 
isolating a single cell in a hanging-drop of the wort-gelatine and watch- 
ing its development hour by hour in the usual way. The results were 
perfectly clear and absolutely conclusive on. this point, as shown in 
figures 4—6 and Fig. 13, 14. The yeast-cell itself is long oblong or 
cylindric-ovoid (Fig. 4a), and varies in size from about 3 by 1 yp to 
5 by 15 pw or even 6—7 by 2 m, depending on the vigour and nu- 
trition. It is extremely delicate, and when young and active is filled 
with hyaline protoplasm devoid of evident granules, oil-drops or 
vacuoles, though these may appear later, and under certain conditions 
the contents may be very oily (Fig. 12). 
It is quite easy to obtain the yeast-cells in pure culture, since they 
are at once washed out of their slimy matrix in water and can be 1so- 
lated in the ordinary way. 
Thus sown in wort-gelatine at ordinary temperatures, the cell buds at 
one end in a few hours (Figs. 4—6), and repeats the process usually at 
the other pole soon afterwards ; each daughter-cell may then again re- 
peat the process, and new buds arise from the parent, and so on until 
a small colony results. (Fig. 3 @.d.) It depends upon the food 
material, temperature and other conditions how long this budding pro- 
cess continues, as well as how rapid the formation and separation, etc., 
of the cells are. Thus in wort-gelatine at ordinary temperatures it 
may require three hours and less to complete a bud, whereas on a poor 
food-medium, or if the temperature is high—z22°C and over—it may 
take a day or more. Compare Figs. 4—6 with Fig. 7. I may add that 
it is frequently the case that fungus cultures are attempted at too high 
a temperature, and abnormal results are obtained; it is by no means 
certain that in the present instance I have succeeded in obtaining the 
optimum temperatures, but growth goes on very well at those given. 
In the course of 24 to 36 hours or so, when a small colony of yeast- 
cells has been formed, some of the marginal cells change their mode of 
growth and the buds no longer separate but elongate into radiating 
hypha—Fig. 4 e, Fig. 5 ¢, Fig. 6 d, and Fig. 6a. It is these hyphe 
which, rapidly increasing, form the halo-like fringe around the colony 
(Figs. 13 and 14). Each hypha is about 1-1'5 mw in diameter, sinuous 
and septate, and soon branches below the septa (Fig. 14). As soon 
as the halo of hyphe is well developed—z.ec., about the third day in 
good cultures—the older of them begin to form chlamydospores, by 
dilating at the tips into pyriform or ovoid swellings full of translucent 
protoplasm, in which minute oil-drops rapidly form, enlarge, and run 
together (Fig. 15). | Very often the apex is prolonged into a short 
beak (Fig. 15), which may grow on and repeat the process (Fig. 2), 
but in other cases the terminal swelling remains rounded at the tip 
(Fig. 2). Every transition may be found between terminal rounded or 
globoid chlamydospores, with or without the beak, and intercalary 
ones, often in series (Figs. 2 and 3). As they get older the wall 
thickens and the oily-drops become more evident, often presenting 4 
curiously striking resemblance to spores in a sporangium (Figs. 3 and 

