218 Barker.—A Fragrant ‘Mycoderma ’ Yeast , 
surface of the gelatine grow in the form of small domes, to 
about the size of a pin’s head. Growth then takes place over 
the surface of the gelatine, and a thin flattened disc is pro¬ 
duced. Sometimes it is circular in outline, glistening white 
in colour, and dry in appearance, marked by radial and 
concentric markings, and with regular edges (Plate XIII, 
Fig. 4). Sometimes it is like the preceding, except that it is 
semi-transparent, moister looking, more film-like, and with 
less regular edges. In other cases the colony is like an 
irregularly circular film, with crenate edges, semi-transparent, 
moist looking, with indications of radial and concentric zones 
(Fig- 3 )- 
Colonies intermediate in character between the above forms 
have been observed. The form seems to be dependent on 
several different factors. The consistency of the gelatine has 
undoubtedly a great deal to do with the ultimate form. Plates 
were made with five per cent, gelatine instead of ten per cent., 
and the most usual form of colony produced in this case was 
the third described above. An abundance of moisture and 
higher temperatures (21-22° C.) tend towards the production 
of the same form. Colonies of the first form described have 
been observed to change into the other forms on increase 
of temperature. 
On laevulose-Mayer gelatine the young stages of the 
colonies are similar to those on beer-wort gelatine. Instead, 
however, of the tiny dome-shaped colonies developing into 
flattened discs, as on beer-wort gelatine, they continue to 
grow in a dome-shaped manner, and in colour are glistening 
white. As they age, their surfaces are pitted with numerous 
tiny depressions, and at a later stage are fluted in a radial 
and concentric direction. They eventually become cone- 
shaped, or else develop a depression at the top of the dome. 
(See Figs. 1 and 7.) 
In old colonies, as a rule, longitudinal splits are formed and 
they fall away into segments. Sometimes, however, they 
lose their white colour with age, becoming brown, and have 
a moist appearance, partially losing their shape. In a few 
