34 DISTINCTIOV BETWEEN PLANTS AND ANIMALS. 



indeed, that it becomes a matter of difficulty to ob- 

 serve them closely. Some have the power of dart- 

 ing about with astonishing velocity, others unceas- 

 ingly gyrate, or waltz around with the grace of a 

 Cellarius ; while not a few content themselves by, 

 slug-like, dragging their slow length along. The 

 last are frequently startled from their propriety and 

 aplomb by the rapid evolutions of their terpshicorean 

 neighbours. Some, again, grasping hold of an object 

 by one of their long filaments, revolve rapidly round it, 

 whilst others spring, leap, and perform sundry feats 

 of acrobatism that are unmatched in dexterity by any 

 of the larger animals. 



I may here observe that the motions and general 

 structure of many of the microscopic forms of vegeta- 

 tion, so much resemble those of some of the infusoria, 

 that it has long puzzled naturalists to distinguish be- 

 tween them with any degree of certainty. The 

 chief distinction appears to lie in the nature of their 

 food. Those forms which are truly vegetable can 

 live upon purely inorganic matter, while the animals 

 require that which is organized. The plants also 

 live entirely by the absorption of fluid through the 

 exterior, while the animalcule are capable of taking in 

 solid particles into the interior of the body. Their mode 

 of multiplication, and the metamorphoses they under- 

 go, are much alike in both classes, being, during one 

 stage of their existence, still and sometimes immov- 

 ably fixed to stones, sea- weed, &c., and at another 



