30G NATURAL THEOLOGY. 



velocity, or sink under the surface, and move only with the cur- 

 rent. There is every reason to believe that the air, which is the 

 principal means of change of place, is secreted by the animal. 



From some of these animals tentacula hang down into the wa- 

 ter for seizing their food, and perhaps for directing their progress. 

 They have a power of distending them, or erecting them by 

 orcing water into their texture, by the contraction of vesicles near 

 their base. Varieties of these animals hoist a plate or crest out 

 of the water, which has a still greater resemblance to a sail. 



We have alread}'^ noticed the fins of fishes, the wing of the 

 bird, and the web-foot of the duck. " The meanest creature is, 

 indeed, a collection of wonders." In the earth-worm or the cater- 

 pillar, the head, or the anterior part of the body, is projected (and 

 it is a dfficult problem to produce extension by contraction) till it 

 touches the ground, and slightly adheres to it, when the posterior 

 part of the body is drawn forwards. In many wonus or cater- 

 pillars there are holders discoverable upon minute inspection, and 

 their anatomy exhibits a perfect set of muscles attached to those 

 exterior rough points, — by which it is made evident that each of 

 them is a foot. But nothing is more interesting than to see the 

 change of the larva to the winged insect, where these muscles 

 and their appropriate nerves disappear : and new muscles, and 

 new nerves, and new energies direct the creature that crept an 

 inch in an hour to outstrip, as we have said, the fleetest horse or 

 to rise upon the wind ; for those who travel by the new rail-roads 

 obser\'e bees lo fly round them, and therefore to move above sixty 

 miles an hour. The contrasts are the most curious between the 

 flight of the bat and the motion of the mole ; the same organiza- 

 tion being calculated, with slight adaptation, for the atmosphere, 

 and for moving under the earth. We might almost give the in- 

 stance of the perforation of solid calcareous rock by the boring 

 mollusca, which, by late observations, seems to be accomplished 

 by means of the foot. 



