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-contractile, finely perforate at their ex- 

 tremities. Increasing by gemmation. . Dendrocometes Stein. 

 Representative species. . . Dendrocometes 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 pio- 

 toplasm of their bodies absorbed into the body of the 

 host. Nucleus subtriangular. Diameter of body 8o/z. 

 Fresh water, sometimes attached to Gammarus pulcx, a 

 fresh-water shrimp. 



FlC, S53. Dendrocometes paradoxus. X 170. (After Stein.) 



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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 Miiller 1786. 



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. Diameter of body 55 M. Attached to aquat- 

 ic plants. 



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

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



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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 n. Attached to 

 aquatic plants. 



FIG. 555. Dendrosoma radians. X 30. (After Blochmann.) 



215 (214) Not forming colonies 



