122 



PROTOZOA 



The agitation of the flagellum determines a stream of water 

 upwards along the outer walls of the funnel; and the food- 

 particles brought along adhere to the outside of the funnel, and 

 are carried by its streaming movement to the basal constriction, 

 where they are swallowed by the plasma, which appears to form 

 a swallowing vacuole at that point. Longitudinal fission is the 

 ordinary mode of reproduction, extending up through the funnel. 

 If the two so formed continue to produce a stalk, the result is 



LMonosiga. 2.Salpingoeca. 3.Polyoeo8. 4.Proferospongia. 



Fig. 40.— Various forms of Craspedomonadidae. 2, a, Adult cell ; 2, 6, longitudinal 

 fission ; 2, c, the production of flagellulae by brood-formation ; c, collar ; c.vac, con- 

 tractile vacuole ; fl, flagellum ; I, theca ; nu, nucleus ; s, stalk. (After Saville Kent.) 



the formation of a tree-like stem, whose twigs bear at the ends 

 the funnelled cells, or " collar-cells " as they are usually called. 

 In Salpingoeca, as in so many other Flagellates, each cell forms a 

 cup or theca, often of most graceful vase-like outline, the rim 

 being elegantly turned back. Proterospongia (Fig. 75, p. 18 2) 

 secretes a gelatinous investment for the colony, which is attached 

 to solid bodies. In this species, according to Saville Kent, the 

 central members of the colony retract their collar, lose their 

 flagellum, become amoeboid, and finally undergo brood-formation 

 to produce minute zoospores. This is the form which by its 

 differentiation recalls the Sponges, and has been regarded as a 



