THE GREEN HYDRA. 57 



been hitherto supposed. When thus highly magni- 

 fied, the granules are visible in its texture, arranged, 

 as the reader will observe, in distinct layers, and 

 appropriated, M. Gervais thinks, to different offices. 

 Hence he concludes that while the external layers 

 serve as a covering to the animal, the internal, 

 composed of particles of a conical form, subserve 

 the digestive process. It is, therefore, highly pro- 

 bable, that the structure of the green hydra is no 

 less complicated. Arranged about the mouth are 

 some fine filaments which act as arms. 



This animal is affected by light, and when con- 

 fined in a glass, always seeks its brightest side. Its 

 favourite position appears to be that of remaining 

 suspended from the surface of the water, by means of 

 its lower extremity, called its foot. It is manifestly 

 conscious of fear, for when touched roughly, it con- 

 tracts itself into a small globule, in which state it is 

 secure, as it may easily escape observation. It can 

 wander about the water at pleasure, but its usual 

 mode of proceeding along the stems or leaves of 

 plants is slow. It fixes the sucker of its foot, so 

 as to attach itself firmly, and then gently bending 

 down the body, it describes a semicircle till the 

 mouth reaches another part of the stem or the 

 leaf on which it is stationed ; then adhering by the 

 mouth, or the arms arranged about it, it unfixes the 

 sucker, draws it close to the mouth, and fastens it 

 again ; once more, it elevates the body, bends it 

 down, and adheres by the arms, and brings the 

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