NATURAL THEOLOGY. 305 



Other animals, proofs of new and appropriate me- 

 chanism. Suppose that we had never seen an ani- 

 mal move upon the ground without feet, and that 

 the problem was: Muscular action, i. e., reciprocal 

 contraction and relaxation being given, to describe 

 how such an animal might be constructed capable 

 of voluntarily changing place. Something, per- 

 haps, like the organization of reptiles might have 

 been hit upon by the ingenuity of an artist ; or 

 might have been exhibited in an automaton, by 

 the combination of springs, spiral wires, and ring- 

 lets : but to the solution of the problem would not 

 be denied, surely, the praise of invention and of 

 successful thought : least of all could it ever be 

 questioned whether intelligence had been employ- 

 ed about it or not.'*^ 



''0 Not unconnected with the subject of the last note is the pro- 

 gression of animals : and we have none better suited for the ob- 

 ject of this volume than the consideration of the infinite variety of 

 the instruments of motion, from the blubber that floats like froth 

 upon the water, to the eagle or the antelope. The genus medusa of 

 Linnaeus embraces those animals like jelly which float in the sea. 

 Some of these, when taken out of the water, will weigh fifty ounces, 

 and, on being dried, not more than five or six grains. From this it 

 would appear that they must be of the specific gravity of water, 

 and hence their peculiar organization and mode of existence; 

 especially it accounts for their mode of progression, if it can be 

 called so : since they are in a great measure passive, and float 

 and are carried by the wind. For this purpose there is a vesicle 

 or bladder filled with air, which in some rises above the water, 

 and the animal is dragged as we might imagine a balloon would 

 be after lighting on the water. The walls of this sac are muscu- 

 lar, and the animal, by retaining or forcing out the air, can either 

 take advantage of the wind, and is sometimes moved with great 



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