INFUSORIA. 449 



stems and filaments of the -svatcr-plants, or crawls upon 

 the surface of the live-box. It does not appear to 

 change its form, otlierwise than its soft and flexible 

 body necessitates, as it twines abont. 



But enough of the Eaijlcnas. For I have just caught 

 sight of a still more curious creature, the Swan Ani- 

 malcule {Tracheloeerca olor). It is reposing on one 

 of the leaves of the Myriopliyllum^ its long and flexible 

 neck lengthening and contracting at pleasure, the tip 

 thrown about in quick jerks, in every direction, some- 

 what like a caterpillar when it touches several points 

 impatiently with its head. 



If we admire the graceful sailing of a swan upon a 

 lake, the swelling of its rounded bosom, the elegant 

 curves of its long neck, we shall be struck with the 

 form and motion of this animal. The foi'm has much 

 resemblance to that of a swan, or still more to that of a 

 snake-bird {Plotus) ; the body, swelling in the iniddle, 

 tapers gradually into a slender pointed tail, at one ex- 

 tremity, and at the other, into a very long and equally 

 slender neck, which is terminated by a slight dilitation. 

 The whole is ])erfectly transparent, but the body is 

 filled with numerous minute globular vessels, or tempo- 

 rai'y stomachs. The grace of its motion as it glides 

 along with a free and moderately swift progression 

 through the clear water, or winds through the intricate 

 passages of the green conferva, throAving its long neck 

 into elegant curves, is very remarkable. There are, I 

 see, two of them, which however take no notice of each 

 other, even Avhen passing close to each other ; the neck 

 of one is much longer than that of the other, Now 

 and then, when gliding along, the neck is suddenly 

 contracted, but not wholly, as if something had alarmed 



