THE MICROSCOPE IN ZOOLOGY. 161 



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called poly gastric animalcules. Yet a large section de- 

 scribed by him in this connection, including the Desmidi- 

 acece, Diatomacece, Volvocinece, and other protophytes, have 

 been transferred by naturalists to the vegetable kingdom. 



The bodies of the Infusoria consist of sarcode or bio- 

 plasm, having an outer layer of firmer consistence. Some- 

 times the integument is hardened on one side so as to form 

 a shield, and in other cases it is so prolonged and doubled 

 upon itself as to form a sheath or cell, within which the 

 animalcule lies. The form of the body is more definite 

 than that of Amoeba, so as to be characteristic of species. 

 It may be oblong, oval, or round ; and some kinds, as 

 Vorticella, are attached to a footstalk, which has the power 

 of contracting in a spiral coil. No distinct muscular 

 structure can be detected in the Infusoria, yet the general 

 substance of the body is contractile. In most species 

 short hair-like filaments or cilia project from the surface, 

 sometimes arranged in one or more rows round the mouth, 

 and moving to all appearance under the influence of voli- 

 tion. In others there are one or two flagelliform filaments, 

 or long anterior cilia with vibratile ends. Others, again, 

 have setse or bristles, which assist in locomotion. The 

 motions of some are slow, and of others quite rapid. 



The interior of the sarcode body exhibit certain round- 

 ish spots, sometimes containing Diatoms or other foreign 

 substances. They have been called gastric vesicles, cells, 

 spaces, or sacculi. They are only visible from their con- 

 tents, and seem to be mere spaces without a living mem- 

 brane. If a little indigo or carmine is diffused in the 

 water which contains the Infusoria, the cavities will soon 

 be filled and become distinct. If watched carefully they 

 will appear to move round the body of the animal, and as 

 the pigment escapes at some part of the surface, the spots 

 will disappear. Ehrenberg regarded these spots as so 

 many stomachs arranged about a common duct, but the 

 common opinion at present regards them as temporary 



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