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EV G Vi. t A 
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STAGES OF GREGARINA 
ZOOLOG Y. 21 
MONERA, 
The simplest forms of life known are the Monera (Figs. 
I, 2, 3), which may be defined as living jelly,—formless, 
structureless, in every sense of the word. Their move- 
ments are restricted to a gliding or crawling, a drawing in 
or putting out of their jelly-li 
— 
«e body ; their reproduction 
is a simple splitting of their body into two halves, each half 
becoming a new Monas. Such a living slime is seen in 
Protogenes. The first sign of structure we meet with 
in this kind of being is where a wall has been exuded 
inclosing the jelly-like body, as in Protomonas, or as in 
Amoeba (Figs. 4, 5, 6, 7), where the slime has aggregated 
in the middle, forming a nucleus. These two different 
conditions, a nucleated slime and a walled slime, are com- 
bined in Arcella, these last being undistinguishable from 
the young of the simplest water-plants (Algae) and the un- 
developed forms of certain jelly-fish (Siphonophora). In 
the springtime the ponds are often covered with a green 
matter, which, when examined with a microscope, is found 
to consist of Euglena (Fig. 8), minute flask-shaped bodies 
with little tails; when these bodies are covered with 
hairs (cilia) they are known as Peridnium. They, like the 
Arcella, cannot be distinguished from the young of the 
simplest plants and animalcula (Infusoria). What conclu- 
sions can be drawn from the existence of Monera, Amcebe, 
Euglena? How have they originated? Either they have 
come from pre-existing forms, or have arisen through 
spontaneous generation. Where have the pre-existing 
forms come from, is immediately suggested by the first 
answer, which only waives the question, and is therefore no 
answer at all. It will not suffice to say that they were 
created; as well might an astronomer explain the motion 
of the moon around the earth by saying it was created 
so to move. What is meant by spontaneous generation ? 
