CHAPTER III 
THE SIMPLEST FORMS OF LIFE 
THE simplest conceivable living being is a mass of 
undifferentiated protoplasm, and it was claimed by 
Haeckel and others that such simple forms of life 
do actually exist. Haeckel described under the name 
Monera .a considerable number of organisms to 
which he attributed this simple structure; but the 
great improvements made of late years in microscopic 
technique have shown that these are really much less 
simple than was supposed. A nucleus can in most 
cases be demonstrated, as well as other evidences of 
differentiation. 
There are, however, a good many organisms of such 
simple structure that we cannot positively assert that 
they belong to either the animal or vegetable kingdoms. 
There are in particular two groups of these indifferent 
organisms, those included by Haeckel in his Monera, 
such as Vampyrella and Protomyxa, and those curi- 
ous organisms the “ Slime-moulds,” — Myxomycetes or 
Mycetozoa. These two groups, which are generally 
considered respectively as the lowest of the animal and 
plant series, have a good many characters in common. 
They are all, in their vegetative condition, naked masses 
of soft, slimy protoplasm — “ plasmodia,”—which show 
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