298 



FRESH-WATER BIOLOGY 



208 (i) Cilia present during embryonic stage only. 



Tentacles in adult. 

 Class Suctoria 



209 



209 (210) Tentacles branched. Animals solitary, sessile, discoidal, or sub- 

 spherical, with the surface of the integument indurated. 

 Tentacles flexible, non-contractUe, finely perforate at their ex- 

 tremities. Increasing by gemmation. Dendrocomeles Stein. 

 Representative species. Dendrocomeles paradoxus Stein 1851. 



Tentacles equal in length to the diameter of the body, 

 usually five or less in number. The distal terminations 

 of the tentacles are capable of great expansion and, by 

 means of these, other Protozoa are captured and the pro- 

 toplasm of their bodies absorbed into the body of the 

 host. Nucleus subtriangular. Diameter of body So//. 

 Fresh water, sometimes attached to Gammarus pulex, a 

 fresh-water shrimp. 



Fig. 553. Dendrocomeles paradoxus. X 170. (After Stein.) 



210(209) Tentacles unbranched, contractile. . . 211 



211 (220) Without a lorica. ... 212 



212 (213) With a stalk. Body spherical or pear-shaped. Tentacles knobbed, 



scattered, or in groups. In some species the animal may 

 become detached from the stalk and live a free life. 



Podophrya Ehrenberg. 

 Representative species. . . . Podophrya fixa MuUer iy86. 



Stalk slender but rigid. Tentacles slender, 

 scattered over the surface of the body, usually 

 not longer than the diameter of the body. Nu- 

 cleus oval, central. Contractile vacuoles often 

 two. Diameterof body 55fi. Attached to aquat- 

 ic plants. 



Fig. 554. Podophrya fixa. Active individuals. X 210. 

 (After Conn.) Cyst. X 230. (After Edmondson.) 



213(212) Without a Stalk . 214 



214 (215) Forming colonies. Animals fused, forming an erect, branching 

 colony. Several colonies may be connected by a creeping 

 stolon. Suctorial, capitate tentacles borne on the ends of 



the branches Dendrosoma Ehrenberg. 



Representative species. . . Dendrosoma radians Ehrenberg 1838. 



Stolon repent, giving rise to a number of erect branches 

 tapering distally, themselves often branched. Nucleus ribbon- 

 like, ramifying into the branches. Contractile vacuoles nu- 

 merous. Height of colony 1000 to 2500 ^. Attached to 

 aquatic plants. 



Fig. 5 55. Dendrosoma radians. X 30. (After Blochmann.) 



3IS (214) Not forming colonies 216 



