THE LIFE-HISTORY OF A MYXOMYCETE. 
271 
colour. Concomitantly with this change of tint differentiation 
occurs in the substance, the surface becomes warty, the 
membranes which will ultimately become the “ peridia ” or 
walls of the receptacles are secreted, and within them is 
enclosed the spore plasm. This divides, for the most part, into 
a number of minute fragments which become coated with 
cellulose and form the spores; some portion of it, however, is 
converted into the “ capillitium,” a delicate network of threads 
running amongst the spores, the function of which is not in 
all cases quite clear. Nearly the whole of the plasmodium is, 
in the case of Brefeldia, used up in the formation of the 
receptacles, or “ sporangia ” as they are called, and their 
contents. 
The spores, in the case of Brefeldia, seem to escape 
simply through the decay and breaking down of the receptacle, 
but in some species of Myxomycetes the capillitium assists, 
bv its elasticity, in the rupture of the sporangium and the 
dispersion of the spores. 
The curious mixture of animal and vegetable attributes 
observed in the Myxomycetes, has led some naturalists to give 
them the name ofMycetozoa, or “fungus-animals,” a thoroughly 
appropriate term, for, as we have seen, the organism whose 
history we have been considering, exhibits during two-thirds 
of its life the characteristics of an amoeba, which is unhesi¬ 
tatingly classed among the animals; while in the remaining 
third it so closely resembles the common puff-ball, as actually 
to have received the synonym of Lycoperdon Epidendron— 
“ tree-puff-ball.” We have here one more proof, if more were 
needed, of the impossibility of laying down inflexible lines in 
the classification of natural objects. Classes and divisions 
melt insensibly into each other, and have in fact no real 
existence except as mental conceptions, useful for the orderly 
apprehension of natural phenomena, but limited in their 
application. To a want of recognition of this limit may be 
traced many fruitless and constantly recurring discussions. 
I should like to ask your attention for a few minutes to a 
speculation as to the cause of the remarkable colours assumed 
by the Myxomycetes ; these are principally bright yellow, 
reddish yellow, and black, the latter reached in Brefeldia, 
through deepening shades of purple. There is no doubt that 
light is inimical to the delicate protoplasm of which the 
plasmodium is formed, and it has long been known that some 
species exercise their motile power in order to avoid it. 
Professor Allman in his address to the British Association, 
nine or ten years ago, drew attention to this property in 
Fuligo, or as it was then called iEthalium, the “flowers of 
