INFUSORIA 441 



than its soft and flexible body necessitates, as it twines 

 about. 



But enough of the Euglenas. For I have just caught 

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

 cule (Trachelocerca olor). It is reposing on one of the 

 leaves of the Myriophyllum, its long and flexible neck 

 lengthening and contracting at pleasure, the tip thrown 

 about in quick jerks, in every direction, somewhat 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 form has much resemblance 

 to that of a swan, or still more to that of a snake-bird 

 (Plotus); the body, swelling in the middle, tapers grad- 

 ually into a slender pointed tail at one extremity, and at 

 the other into a very long and equally slender neck, which 

 is terminated by a slight dilatation. The whole is perfectly 

 transparent, but the body is filled with numerous minute 

 globular vessels, or temporary 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, throwing 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 when 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 or displeased the 

 animal: the body also can be swollen or lengthened at 

 pleasure; it can move in either direction, but the neck 



