50 POLYGASTKICA. 



a colourless transparent matter, which seems to harden into horn. 

 The grey matter swells in the centre, where the rays meet, and 

 rises perpendicularly upwards, surrounded by the transparent horny 

 substance, so as to form the trunk of the new zoophyte. The rays 

 first formed are obviously the fleshy central substance of the 

 roots ; and the portion of that substance which grows perpendi- 

 cularly upwards forms the fleshy part of the stem, from which in 

 due time polyps become developed. 



CHAPTER IV. 



POLYGASTRICA. 



ANIMALCULA INFUSORIA. Auct. 



(70.) Previous to the discovery of the microscope, it was little sus- 

 pected that animals existed of such minute size as totally to elude 

 the search of unassisted vision ; much less that every drop of water in 

 which animal or vegetable substances have been allowed to decay, 

 swarms with numberless forms of living beings ; that countless 

 millions inhabit every stagnant pool or running stream ; nay, that 

 every drop of the surface of the ocean is in itself a little world, 

 peopled by innumerable active creatures, as various in their out- 

 ward forms as they are elaborately adapted by their internal organi- 

 zation to the circumstances in which they live. 



The terms Infusoria and Animal cula, as first used by the earliest 

 discoverers of these beings, were applied to an immense number of 

 creatures widely differing from each other in every particular except 

 in the minuteness of their size, which had previously concealed 

 them from observation. The germs of embryo polyps, the larvae 

 of insects, and all microscopic forms of being, including the won- 

 derful tribes of living atoms which inhabit various secretions in the 

 interior of other animals, were thus thrown together in one heteroge- 

 neous and chaotic group, without reference to the structure, rela- 

 tions or habits of the creatures so denominated. This motley 

 assemblage has, however, by subsequent laborious investigations, 

 been separated and arranged so as in some measure to enable us to 

 acquire accurate notions concerning the animals formerly confounded 

 under one common designation. 



