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contiguity of objects, and thus enabling it to 

 avoid them. 



The last subject for consideration at present is 

 Loco-motion, or the function by which animals 

 are enabled to shift from place to place. A very 

 great number of quite the lowest orders of ani- 

 mals, as the zoophytes and corallines, remain in 

 general permanently fixed to the substances to 

 which they are found attached, like plants to the 

 soil ; and even some which shift their place, like 

 the sea-blubber, seem to do so, not actively, but 

 by the motions of the waves in which they live. 

 The great majority, however, even of these tribes 

 employ various means of progression, and each 

 presents something interesting in its manner of 

 effecting this. The motions of the snail are fa- 

 miliar to every body. They are effected by that 

 part of the animal called its foot ; which is no- 

 thing more than numerous muscular fibres of a 

 jelly-like consistence, and quite colourless, as in 

 all invertebral animals, situated on the lower sur- 

 face of the strong membrane in which all the en- 

 trails are contained, and attached, also, to the 

 shell, so that the foot can be either protruded or 

 retracted at pleasure. Its progression is by a 

 vermicular motion ; and it attaches itself to the 

 surface along which it glides, partly by forming 

 a vacuum with the sole of the foot, in the man- 

 ner of a sucker, and partly by a viscid mucilage 

 secreted by the part. The loco-motion of the 



