SPECIAL MORPHOLOGY AND TAXONOMY OF INFUSORIA 377 



widespread. They are aV)iiiidant in fresh-water pools, in brackish 

 water, and more rarely, in salt water. Three sub-orders are 

 recognized according to the nature of the mouth or its absence (1) 

 Astomina, (2) Gymnostomina, and (3) Trichostomina. 



Sub-order 1. Astomina. 

 Parasitic forms. See Key for genera. 



Sub-order 2. Gymnostomina, Butsciili. 



Holotrichs without undulating membranes in the oral region. 

 The mouth is closed except during ingestion of solid food. In 

 several genera longer cilia are present in the form of an oral circlet. 

 The body is not always covered by cilia, which may be present 

 only on one-half the body, limited to rather widely separated spiral 

 rows, or to one side only. This group includes the most generalized 

 forms of the Infusoria with what may be regarded as the original, 

 terminal position of the mouth. The migrations of the mouth, first 

 suggested by Biitschli with the correlated shifting of the longitudinal 

 rows of cilia affords an interesting study in ciliate morphology. 

 The mouth varies from a small terminal orifice in Ilolophrya (Fig. 

 106), Prorodon (Fig. ]()5, (\ 1), F, G) or Didinium, to a slit occupy- 

 ing the entire anterior end in Enchelys (Fig. 166, C). This slit is 

 diagonally placed in Spathidium (Fig. 90, p. 181), drawn down on 

 the side in LoxophyUum (Fig. 167), extended in a long slit down the 

 ventral surface of Amphilepiiis and Lionotus (Fig. 167, A, B) and 

 reduced to a small opening at the base of what may have been an 

 elongated slit, in Dileptus. In the Chlamydodontidae and some 

 Chiliferida? it has shifted over to the right side while the left side 

 is naked. Some forms are covered with a tightl\-fitting cuirass 

 made of sculptured plates, the cuirass dividing with division of the 

 body in Coleps, Tiarina, etc. (Fig. 164). 



Pseudopodia of the axopod type are present in addition to cilia 

 in DactylochJamys and Myriaphrys, and plasticity and elasticity 

 are strikingly characteristic of some types, the mouth region of 

 Lacrymaria olor for example being capable of stretching out, shake- 

 like, a distance equal to three or four times the length of the bod^'" 

 Fig. 76, p. 148). 



The Sub-order is divided in four families: (1) Enchelinidff', (2) 

 Trachelinidie, (3) Chlamydodontidae and (4) Nicolleliidie. 



FamUy 1. Enchelinidae, Ehrenberg, Stein. — Generalized forms 

 with most of the striking peculiarities of the Order; body spherical 

 or ellipsoidal and with little distortion of the regular lines of cilia. 

 Nutrition holozoic with deglutition of solid living organisms. Repro- 

 duction typical of the Class. Common forms: 



