403 



THE INFUSORIA 



is extremely contractile. It forms chitinous tubes attached to Algae and 

 Shells. 1 mm. when fully extended. Marine and sometimes freshwater. 

 (Figs. 62, 62A, 63.) 



Family GYROCORYNA, Stein. Caenomorpha, Perty. The remarkable 

 form of this genus is shown in Fig. 64. Its general relations seem to 

 be with Metopus, one of the Plagiotomina. On the other hand, the absence 

 of cilia from all but localised parts of the body indicates affinities with the 

 OLIGOTRICHA. O'l. Freshwater and marine. Closely allied to it is 

 Caenomorptena, Blochmann. 



az 



SUB-ORDER OLIGOTRICHA. 



In this group the adoral zone 

 is always situated at the free or 

 anterior extremity of the body. In 

 nearly all forms there are areas or 

 tracts of the surface of the body 



az- 



Fio. 63. 



Follicullna ampulla, C. and L., expanded. 

 ., the bilobed adoral zone ; t, the test ; 

 c.v, contractile vacuole ; M, meganucleus. 

 (After Stein.) x ca. 150. 



FIG. 64. 



Caenomorpha medusula, Perty. From 

 the ventral side, slightly turned to the 

 right, a.z, adoral zone ; c.v, contractile 

 vacuole ; M, meganucleus ; m, micro- 

 nucleus ; c, cirri. (From Biitschli, after 

 Blochmann.) x 300. 



free from cilia, and in a considerable number of genera there are 

 localised tufts of cilia (Gycloposthium) or spinous processes of the 

 body-wall (Ophryoscolex). The body is very variable in shape, and no 

 particular form of it can be regarded as characteristic of the sub- 

 order. The sub-order includes a large number of species (TiNTixxoiNA, 

 etc.) of small size which occur in the plankton of the sea and lakes. 

 These animals very frequently exhibit curious and very characteristic 

 darting movements alternating with periods of immobility. Several 

 genera are internal parasites. The meganucleus is usually a single large 

 oval body, and is accompanied by one micronucleus. 



The OLIGOTRICHA are divided into the following families : 

 Family LIEBERKUHNINA (?), Biitschli. Biitschli founded this family 

 to include certain spherical forms with a spiral adoral zone which were 



