MICROSCOPE AT THE POND -SIDE. 65 



animalcules, and press them into the fleshy sub- 

 stance in its centre. This is undoubtedly an animal, 

 but it has no mouth or stomach. A large number 

 of such forms present themselves under the Micro- 

 scope. Some of them are covered with an external 

 envelope, which they make artificially, by attaching 

 small stones and other substances to their external 

 surface, as in the case of the Difflugiae, seen at 

 figure 18, plate 1 ; or they may form a regular 

 case, or carapace, consisting of a hairy membrane, 

 as in Arcella, represented at figure 19. We shall 

 meet again with forms resembling these when wo 

 take our Microscope to the sea- side. 



One of the most common animalcules met with 

 in fresh water, and whose presence can easily be 

 insured by steeping a few stalks of hay in a glass 

 of water, is the bell-shaped animalcule. These 

 animalcules, which are called Vorticetta, are of 

 various sizes. Some are so large that their presence 

 can easily be detected by the naked eye, whilst 

 others require the highest powers of the Micro- 

 scope. They are all distinguished by having a 

 little cup-shaped body, which is placed upon a long 

 stalk, figured at 40, in our second plate. The stalk 

 has the peculiar power of contracting in a spiral 

 manner, which the creature does when anything 

 disturbs it in the slightest manner. In some species 

 these stalks are branched, so that hundreds of these 

 creatures are found on a single stem, forming an 

 exceedingly beautiful object with the Microscope. 

 The stalks of these compound vorticellse are con- 

 tracted together, so that a large mass, expanding 

 over the whole field of the Microscope, suddenly 

 disappears, and, " like the baseless fabric of a vision, 

 leave not a wrack behind." A little patience, 

 however, and the fearful creatures will once more 

 be seen to expand themselves in all their beauty. 



