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favour by many, that the earliest specialisations of the primal endowments 
of living organic matter coincide exactly with structural differentiation. 
The classification of the different groups of Protozoa, including all the lowest 
types of animal life is, in our present ignorance of the exact cycle of changes 
occurring in each individual, and of the limits of the several types with which 
we are as yet acquainted, necessarily incomplete. Huxley's first group 
(Monerozoa including Amoebae and Rhizopoda) contains animals in which a 
noticeable advance in organization may be recognised, -when we compare 
the simplest member of the group " Protrogenes " with the typical Amoeba 
princeps, in which a generative organ (nucleus) and a vesicle or vacuole 
are always found present in the diffluent plasm of which its body is composed. 
It is, I think, questionable whether the original notion of a distinct species 
or genus can be retained under the term Amoeba. The occurrence of well- 
recognised Amoeboid stages ia the life history of the other groups of Protozoa, 
and the remarkable alternation of what at one time appears to be vegetable 
at another time animal protoplasm in the body of the same Monad, during 
successive periods of its life, seem to indicate that the Amoeboid state of 
organic matter is a very general phenomenon. If it really be the life-long 
condition of one animal it is certainly but the occasional and transitory con- 
dition of another. On the other hand, this Amoeboid state of organic matter 
is as certainly associated with a definite constitution of the organic compound, 
and with an equally specific manifestation of vital properties. Contractility 
is perhaps the most fundamental endowment of the simplest and entirely 
structureless particle of living protoplasm. But the contractility of an 
Amoeba has a method of its own — that is to say, it has become specialised so 
as to exhibit a motility exercised in a particular manner, and apparently 
responds only to special stimuli. The motility of an Amoeba destitute of 
"organs of motion," could hardly be denied a material cause, and this again 
can only be sought for in a specific molecular constitution of its contractile 
substance— i.e. molecular constitution is here the only "structural adapta- 
tion" which stands in place of organ, or instrument of the newly-acquired 
motility. Our finite senses cannot discern any visible apparatus, but we 
must acknowledge the existence of an agent where we see an act performed. 
And whatever be our explanation of vital force, we must admit that its 
physical basis is a material "sui generis." Apart from the animal's power of 
self-preservation, growth, and propagation, the chief characteristic of the 
Amoeboid state of animal matter is its peculiar motility, derived, so to speak, 
from the primal endowment of contractility, and the loss of this character is 
always coincident with some change of organic constitution of the living 
plasm. Another kind of motility we find associated with corresponding 
