412 MICROSCOPIC FORMS OF ANIMAL LIFE. 



(p. 48). One of the first and most important results of his study, 

 and that which has most firmly maintained its ground notwith- 

 standing the weakening of Prof. Ehrenberg's authority in other 

 respects, was the separation of the entire assemblage into two 

 distinct groups, having scarcely any feature in common except- 

 ing their minute size, one being of very low, and the other of com- 

 paratively high organization. On the lower group he conferred 

 the designation of Polygastrica (many-stomached), in conse- 

 quence of having been led to form an idea of their organization, 

 which the united voice of the most trustworthy observers now 

 pronounces to be erroneous ; and he not only assigned to them 

 a complex digestive apparatus, but considered them to be en- 

 dowed with genital organs, nervous .ganglia, and organs of 

 special sense, for none of which can any adequate basis be found 

 in the appearances that the Microscope brings into view within 

 their bodies. Hence it seems desirable to abandon the term 

 "Polygastrica," as conveying an erroneous idea of the structure 

 of these beings ; and we may appropriately fall back on the 

 name Infusoria, or Infusory Animalcules, which simply expresses 

 their almost universal prevalence in infusions of organic matter. 

 For although this was applied by the older writers to the higher 

 group as well as to the lower, yet as these are now distinguished 

 by an appropriate appellation of their own, and are, moreover, 

 not found in infusions when in that state of rapid decomposition 

 which is most favorable to the presence of the inferior kind of 

 Animalcules, it may very well be withdrawn from them, and be 

 restricted to the Polygastrica of Ehrenberg, which is the sense 

 wherein it has been used by many recent writers. To the higher 

 group, Prof. Ehrenberg's name Rotifera or Rotatoria is on the 

 whole very appropriate, as significant of that peculiar arrange- 

 ment of their cilia upon the anterior parts of their bodies, which 

 in some of their most common forms, gives the appearance 

 (when the cilia are in action) of wheels in revolution ; the group, 

 however, includes many members, in which the ciliated lobes 

 are so formed as not to bear the least resemblance to wheels. 

 In their general organization, these "Wheel-animalcules" must 

 certainly be considered as members of the Articulated division 

 of the Animal Kingdom ; and they seem to constitute a class in 

 that lower portion of it, to which the designation Worms is now 

 commonly given. Notwithstanding this wide zoological separa- 

 tion between the two kinds of Animalcules, it seems most 

 suitable to the plan of the present work, to treat of thm in con- 

 nection with one another; since the Microscopist continually 

 finds them associated together, and almost necessarily ranges 

 them in his own mind under one and the same category. 



266. Infusoria. This term, as now limited by the separation 

 of the Rotifera, is applied to a far smaller range of forms than 

 that which was included by Prof. Ehrenberg under the name of 

 " polygastric" animalcules. For a large section of these, in- 



