114 The Microscope. 



in an imperfect state, were classed together. The 

 name Animalcule was given to them, and applied to 

 a heterogeneous assemblage, including not only the 

 true animalcules, but a number of minute plants, 

 crustaceans, and larvae. One by one these have been 

 removed, and referred to other positions. It was an 

 easy matter to do this with regard to many of the 

 crustaceans and larvae, but the case is different with 

 a few of the plants, and also with some of the animals ; 

 naturalists are by no means agreed about the classifica- 

 tion of these, because thorough and complete observa- 

 tion of each species is necessary, to trace out its life- 

 history, before its place in the scale of creation can be 

 ascertained. There are numerous animalcules about 

 which this kind of observation has never been made ; 

 a wide field of research is therefore open to the micro- 

 scopic student. 



The word animalcule, if we look at its derivation, 

 is nothing more than "wee animal," but it has a 

 distinct meaning ; for it includes just two well-marked 

 tribes of minute living creatures, to which the names 

 of Rotifera and Infusoria may be given, and excludes 

 certain perplexing little forms which are seen to move, 

 and yet generally set down as plants ; and also certain 

 small animals which are essentially different in struc- 

 ture from the rotifers and the infusoria, and are 

 designated the " root-footed," or Rhizopods.* These 



* The classification adopted by Dr. Carpenter is here followed. 

 The two groups of animalcules, "having scarcely any feature in 

 common except their minute size," and one being of very low and 

 the other of comparatively high organization, were first recognized 



