416 



THE INFUSORIA 



difficulty in distinguishing between true specific characters and local 

 variations, a great many of the described species are not generally 

 recognised as distinct. 0'2 in height. Cosmopolitan in freshwater, also 

 marine. Carchesium, Ehrb. "With contractile, branched, and colonial 

 stalks. The colonies sometimes 4 mm. in height. Attached to freshwater 

 plants and animals in Europe and N. America. Zoothamnium, Ehrb. 

 In Carchesium every new individual that is formed secretes its own 

 peduncle, and retains its power of independent contraction. In Zootham- 

 nium, on the contrary, the peduncle of the parent splits during fission 

 as far down as the next branch, and the colony retracts as a whole. 

 Individuals 0'08. Colonies sometimes several mm. in length. Marine 

 and freshwater. Glossatella, Biitschli. Stalk very rudimentary. An 

 enormous undulating membrane round the 

 peristomial margin. 0'04. Attached to 

 Triton larvae. Epistylis, Ehrb. Forming 



FIG. 81. 



FIG. 82. 



81. Cothurnia (Pyxi- 

 cola, Kent) affinis, Kent. 

 Expanded, x, operculum. 



82. Cothurnia (Pyxi- 

 cola, Kent) affinis, Kent. 

 Retracted, x, operculum 

 closed. 



Fio. 83. 



Co</M<rnia(Thuricola) val- 

 vata, Wright. On the left 

 two expanded individuals 

 are, as a result of fission, 

 temporarily occupying one 

 tube, u, valve. On the 

 right, the same retracted, 

 the valve it closed like the 

 door of a trap-door spider's 

 nest. 



colonies similar to those of Carchesium, but with non-contractile peduncles. 

 (Figs. 78 and 79.) Colonies 4 mm. in height. Individuals O8. Princi- 

 pally found attached to freshwater animals. (Figs. 78 and 79.) Ehabdo- 

 styZa, Kent. Similar to Epistylis, but solitary. -09. On larvae of Diptera. 

 Opercularia, Stein. (Fig. 80.) The disc is oblique, and the peristome is 

 provided with an undulating membrane. Peduncle as in Epistylis, branched 

 and rigid. 0'25. Freshwater. Campanella, Goldfuss. The adoral zone 

 of cilia greatly developed, forming five complete turns. 0'15. 

 Colony 4 mm. Freshwater. Ophrydium, Ehrb. (Fig. 2.) Colony 

 secreting a common mucilaginous test. 0'4. Freshwater. Cothurnia, 

 Clap, and L. Individuals secrete a cylindrical test, provided with a 

 lid which can shut down over the contracted individual. (Figs. 81, 82, 83.) 

 0*4. Marine and freshwater. Cothurniopsis, Entz. Individuals usually 

 more isolated than in Cothurnia. Commonly found on the gills of Astacus 



