108 TlMEHRI. 
that common and general experience has shown to be 
the most suitable. 
At the very commencement, one form, the Proteus- 
animalcule, will be selected as a representative of the 
whole group of the Animalcules ; and after the examina- 
tion of its structure and life history, it will remain as a 
type before us, while the other forms are reviewed ; and 
we shall be enabled to pi6lure, by an unscientific use of 
the imagination, the silent pity with which it regards 
those lower in the scale of organisation, the free and 
genial recognition which it gives to its compeers, and the 
doubtful tribute of admiration which it offers to its supe- 
riors, as they pass before it. 
The Proteus-animalcule is before us ! and we are at 
once struck with the simplicity of strufture that meets 
us, as we gaze at it through the microscope. The first 
view shews us something that looks very much like a 
small quantity of liquid spread out on the surface as a thin 
layer, having a very irregular outline, the marginal part 
quite clear, while the inner part is crowded with various 
sorts of granules and particles. This apparent liquid is the 
thin jelly-like protoplasm. The very next moment, the 
outline is observed to alter, and if it be carefully watched 
no difficulty will be met with in interpreting the change 
that occurs, though this alteration will vary slightly 
according to the exaft kind of Proteus-animalcule that 
is examined. 
In one species, the alteration is seen to consist in the 
protrusion of a small portion of the fluid substance, and 
this portion increases until the rest of the fluid substance 
has, so to speak, run into it. But, meanwhile, other pro- 
trusions have been taking place chiefly along the outline 
