10
INTRODUCTION.
In a few instances a large nucleus encloses two nucleoli, and
occasionally there are appearances which strongly suggest that
simple division of a nucleus is taking place. Some days later,
when the plasmodium had ceased to feed, and was collecting
together to form into sporangia, stainings showed the nuclei more
equal in size, measuring 4 to 5 /л in diameter. This experiment
may be taken to add materially to the negative evidence, to say
no more, that under some conditions the increase in the number
of the nuclei is produced by simple division.
The plasmodium of the exosporous Ceratiomyxa issues from the
interior of rotten wood to form cushion-like heaps which rapidly
extend into columnar or branching sporophores. A s the stream­
ing movement common to both divisions of the Mycetozoa is not
described by Famintzin and Woronin in their valuable paper on
Ceratiomyxa before alluded to, the following observations may be
given. Rounded cushions of plasmodium were placed on a coverslip, supported at the margins by wet blotting-paper, and were
thus enclosed in a moist chamber. The plasmodium spread in a
film over the glass, and here eventually an abundant growth of
spores was produced. A t the earliest stage that could be ob­
served under the microscope the plasmodium was seen to be
sharply differentiated into two elements—a hyaline part which
ultimately forms the principal constituent of the gelatinous
column, and the granular protoplasm containing numerous small
nuclei. In the film on the cover-glass the granular substance
spread in a network of veins through the hyaline portion. Through
these veins the protoplasm streamed in rhythmic flow, first in one
direction and then in the other, at the same intervals of time as
in the Endosporece.
The Sclerotium.—Superficial plasmodia may pass into the resting
stage or sclerotium, and this change may be induced by exposure
to dry air.
In some eases, however, it occurs when water and
apparently food material are present, and the cause for the change
is then difficult to discover. When the plasmodium of Badhamia
utricularis is dried, the streaming movement gradually ceases,
and the granular particles collect in clusters, surrounded by a
border of hyaloplasm; the refuse matter is thrown out, and a
membranous cyst-wall forms round each cluster of granules,
which also includes 10 to 20 nuclei; the cysts become agglomer­
ated into thick masses of irregular shape, drying to a horny
consistence.*
The changes of outline seen in the maturing
sclerotia cannot be merely the effect of shrinking from drying,
and as under the microscope we frequently observe the cj'sts
along the margin of a forming sclerotium creep among each other
with amoeboid movement, it is probable that this movement takes
place throughout the mass. The sclerotium of this species can
be revived after preservation in a dry state for three years, by
* Lister, " On Plasmodium o£ Badhamia and Brefeldia," Ann. Hot., vol. ii.,
1888, p. 13.