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NATURAL CARVINGS. 429 
The Gregarinida, so called from a Greek word meaning 
a flock, on account of the mode of congregating together 
which these creatures possess, "are among the simplest 
forms of animal life of which we have any knowledge. 
They are the inhabitants of the bodies of other and larger 
creatures, and are commonly to be found in abundance in 
the alimentary canal of the common cockroach, and in earth- 
worms. They are all microscopic, and any one of them, 
leaving minor modifications aside, may be said to consist of 
à sac, composed of a more or less structureless, not very 
well-defined, membrane, containing a soft semi-fluid sub- 
stance, in the middle, or at one end, of which lies a delicate 
vesicle; in the centre of the latter is a more solid particle." 
This is the whole of the anatomy of these creatures, no 
mouth nor organs of any kind being apparent, so that they 
are placed at the point where it may be said that animal life 
awns, 
Next to the Gregarinida, in the scale of being, stand the 
Rhizopoda. “It seems difficult to imagine a state of organi- 
zation lower than that of the Gregarinida, and yet many of 
the Rhizopoda are still simpler. Nor is there any group 
of the animal kingdom which more admirably illustrates a 
very well founded doctrine, and one which was often advo- 
cated by John Hunter, that life is the cause and not the 
consequence of organization; for, in these lowest forms of 
animal life, there is absolutely nothing worthy of the name 
of organization to be discovered by the microscopist, though 
assisted by the beautiful instruments that are now con- 
tucted. In the substance of many of these creatures, 
hothing is to be discerned but a mass of jelly, which might 
be represented by a little particle of thin glue. Not that it 
Corresponds with the latter in composition, but it has that 
texture and sort of aspect; it is structureless and organless, 
nd without definitely formed parts. Nevertheless it pos- 
Sesses all the essential properties and characters of vitality ; 
it is produced from a body like itself; it is capable of assim- 
