SOILS AND MOKSES OF SPITSBERGEN. 465 
In old cultures the organisms often lose their sp)herical shape and become 
very narrow, tapering particularly at the anterior end (text-fig. 2). In this 
condition the collar is difficult to observe, and often appears to be completely 
merged in the cell protoplasm. Even in the more typical spherical form 
the collar is occasionally invisible, and at death it is invariably comjiletely 
retracted. 
In the living organisms the nucleus, when it is visible, is composed of a 
single spherical karyosome surrounded by a narrow clear zone. Unfor- 
tunately it has only been possible to obtain a single stained preparation in 
which the karyosome was often vacuolated (PI. 24. fig". 14) or distorted by the 
pressure of large cytoplasmic vacuoles (PI. 24. fig. 15). The fixation of these 
specimens appeared to be satisfactory, but until further preparations have 
been obtained, it is impossible to say whether or not these appearances are 
abnormal. 
In its sedentary phase the organism becomes surrounded by a thick 
gelatinous layer. Unlike P. consociatum and P. digitatum it does not form 
any definite colonies, though frequently a number of these gelatinous 
capsules are formed side by side. Frequently als,o two or more cells occur 
in a single capsule, but the process of multiplication has not been observed. 
The flagellum projects through the wall of the capsule, which has no well- 
defined opening, and its fine whip-like distal portion lashes vigorously with 
a spiral movement, which causes cocci etc. to be whirled towards its base, 
where they accumulate in a mass which quivers slightly with the movements 
of the i3agellum. The whole gelatinous capsule, in fact, becomes encrusted 
with cocci etc. so that the details of the organism inside are not easily 
distinguished. The collar appears to be rather smaller than in the free- 
swimming form, and may frequently be entirely lost. Neither in the sessile 
nor in the free-swimming phases have any bacteria been observed inside the 
collar, and the mode of nutrition is therefore unknown. While in this 
gelatinous capsule, the organism loses its collar and flagellum and becomes 
enclosed in a thick wall, forming a rather angular cyst, which, however, has 
none of the ridges shown in Cienkowski's figure (11). 
This sj)ecies has also been found in soils from liothamsted and from the 
West Indies. 
Of the other flagellates recorded, Oicomonas termo Ehrenb. is one of the 
most numerous and most ubiquitous soil organisms. Spiromonas angusta (T)nj.) 
Kent, Helhesimastix fcecicola Woodcock & Lapage, and Phyllomitus sp., 
though much less abundant, are not uncommon in soils from other regions. 
Petalomonas angusta (Klebs) Lemm., found in soil sample 3 (1922), does 
not seem to have been found in the soil before, though the nearly related 
Copromonas subtilis Dobell is not uncommon. 
There were in addition a small number of unfamiliar forms which appeared 
in one or more of the cultures, but in such small numbers that a satisfactory 
LINN. JOUKN. — ZOOLOGY, VOL. SSXV. 34 
