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of most zoologists and botanists, which amused itself with 
the affinities in form of similar natural bodies, without 
suspecting their real blood-relationship thus indicated. The 
chief employment of most systematising naturalists consisted 
of endless and utterly useless controversies on the question 
as to whether this or that animal or vegetable form was a 
“good” or a “bad species,” a subspecies or variety, a sub- 
genus or genus, without its occurring to these over-precise 
savans to explain to themselves previously the limits and 
object of these ideas. But now, on the other hand, when the 
untenability of these as absolute ideas, and their proper im- 
portance as relative ideas, are recognised, when the “ acting 
cause” of variation of form is discovered in “blood-relation- 
ship,” the by far higher, more difficult and more interesting 
problem encounters us, that of fixing by the discovery of the 
“natural system” the pedigree and the relations of descent 
of allied groups hypothetically the nearest related. 
This task nowhere encounters more difficulty than in the 
lowest and meanest organisms. It is comparatively easy to 
fix the pedigree of vertebrate animals with apuroximate cer- 
tainty, when compared with the extraordinary difficulties 
which encounter us in the pedigree of the so-called Protozoa. 
While everywhere there definite highly and many-sided 
differentiated systems of organs present firm hold-points, 
here there are no such systems of organs present. While a 
number of classes and orders have long been there recognised 
as truly natural groups, here this can be maintained of but 
few groups. There is a consistent and rich material collected 
by the experience of centuries ; here loose collections of 
isolated facts have become known for barely two decades. 
No wonder therefore if the most horrible confusion prevails 
in the arrangement of these very low organisms, and every- 
body makes a system for himself. 
I have made the attempt in my ‘ General Morphology’ to 
throw some light upon this systematic chaos, by placing, as a 
special division between true animals and true plants, all 
those doubtful organisms of the lowest rank which display 
no decided affinities nearer to one side than to the other, or 
which possess animal and vegetable characters united and 
mixed in such a manner that, since their discovery, an inter- 
minable controversy about their position in the animal or in 
the vegetable kingdom has continued. Manifestly this con- 
troversy becomes reduced to the smallest compass if the dis- 
putable and doubtful intermediate forms are separated for the 
present (although only provisionally) both from the true 
animals and from the true plants, and united in a special 
