MICROSCOPE IN FRESH WATER. 45 



kingdom. They appear to be masses of protein 

 (sarcode) without any cell-wall. If we suppose an 

 amseba to assume the form of a disk, and to send 

 forth tentacles, or minute elongated processes from 

 all sides, we should have the sun animalcule 

 (Actinophrys Sol), (Fig. 17, PI. 1). This curious 

 creature has the power, apparently, of suddenly 

 contracting its tentacles, and leaping about in the 

 water. It can also contract its tentacles over 

 particles of starch and animalcules, and press them 

 into the fleshy substance 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 Microscope. 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 Difflugice (Fig. 18, PI. 1) ; or they 

 may form a regular case, or carapace, of cellulose, as 

 is seen in Arcella (Fig. 19, PL 1). We shall meet 

 again with forms resembling these when we 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 Vorticella, 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 (Fig. 35, PL 2). 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 



