48 Infusoria : What are they ? 



the entire absence of such a faculty or structure among the 

 plants, has rendered practicable the isolation of a very exten- 

 sive series of animal forms, whose members, it is anticipated, 

 may be almost indefinitely augmented. Even as so far 

 known, the number of flagellate Infusoria is as considerable 

 as that of the Ciliata, and promises in the long run to be 

 transformed into a very substantial majority. A long and 

 intimate acquaintance with the flagellate class has enabled 

 me to propose its subdivision into three primary series, which 

 may take rank with the several orders of the Ciliata already 

 enumerated. The characters presented by these Flagellata 

 are indeed far more substantial in kind than those cited in 

 connection with the Ciliata. They relate not merely to the 

 nature and distribution of the locomotive appendages, but to 

 important distinctions in the characters of the ingestive 

 system. Thus in one very extensive series, for which I have 

 proposed the title of the Flagellata-Pantostomata, there is 

 no distinct mouth or oral aperture, food-substances being 

 received indifferently — after the manner of an Amaha — at 

 all points of the cuticular surface. Such genera as MonaSj 

 Heteromita , or Anthophysa afford fitting examples of this 

 Pantostomatous group. In a more advanced section or order 

 the area of food-ingestion, while not distributed over the 

 entu^e surface, nor so limited as to form a distinct mouth, 

 occupies a discoidal interspace of considerable extent at the 

 anterior extremity of the body. It is this order, distinguished 

 by me by the title of the Choano-Flagellata, or " Collared 

 Monads," that embodies those very minute and beautiful 

 forms in which an extremely delicate extensile and contractile 

 collar-like expansion embraces the base of the flagellum, and, 

 through the adhesiveness and circulation of its substance, 

 constitutes a marvellously elaborate and efficient trap for the 

 capture of passing food. For the first discovery of this very 

 remarkable flagellate group Science is indebted to Professor 

 H. James-Clark of America, who, in the year 1866, figured 

 and described no more than four distinct species. A few 

 years later these several types were discovered by myself 

 upon this side of the Atlantic, and, through the devotion of 



