I 
450 MR. W. H. BURRELL ON MYCETOZOA. 
and the cells fuse together to form masses of protoplasm called 
plasmodia. 
Plasmodium has no cell walls ; the contours of the component 
cells are obliterated and they appear to lose their individuality. 
Under certain conditions it becomes dormant, drying up to a wax- 
like consistence (Sclerotium), and it is then observed to divide 
into more or less regular particles, which Kerner suggests may 
correspond with the original myxamcebre. Lister, however, has 
demonstrated that these particles contain numerous nuclei, and 
that when the swarm cells coalesce complete fusion of the proto- 
plasm takes place. Plasmodium is generally colourless ; in some 
instances it is coloured, Badhamia utricularis, one of the most 
common species, being a rich golden yellow, and Trichia fall-ax 
pink. It is saprophytic in habit, rarely parasitic, penetrating the 
substance of rotten wood, or the damp under layers of decaying 
leaves in forests, or sodden straw heaps such as are found in farm 
premises, moving from place to place in search of food by means 
of a peculiar streaming movement, the more fluid portions setting 
up currents which flow steadily in one direction for a few seconds 
and then reverse, with the result that the edge of the mass is 
steadily pushed forward. This movement from place to place can 
easily be watched by keeping in a damp dish. I have frequently 
had specimens under observation, and it is most curious and 
interesting to notice the changes in situation ; sometimes it will 
be on the upper or lower surface of the food material, at another 
time wholly transferred to the sides of the dish ; at one time 
having the appearance of a dense mass of slime, and a few hours 
later covering several square inches with a fine network. Moisture 
is essential to growth and movement; in dry weather it retires 
to the interior of the wood, etc., on which it is feeding, but in 
wet weather, or when mature, it seeks the surface and can readily 
be found. I was interested to learn from Mr. Upcher’s gardener, 
that he has frequently noticed it on decaying leaves collected for 
use in his greenhouses, either the heat of fermentation or the desire 
to assume the fruiting stage driving it to the surface of the heaps; 
he authenticated this statement by bringing me some, last spring, 
in the reproductive stage; lack of careful handling had broket 
up the sporangia, but the fragments and the purple spores were 
unmistakable. 
