50 



THE PROTOZOA 



is probably of endoplasmic origin, and is pushed out from it in a 

 centrifugal direction. As it grows out, the ectoplasm forms a 

 sheath over it, and extends usually some way beyond it. When 

 the pseudopodium is retracted, the axial rod is liquefied and 

 absorbed by the protoplasm. 



Food-capture is effected by the pseudopodia in various ways (see 

 p. 189). In forms with lobose pseudopodia they flow round the body 



to be ingested, enclosing it 

 on all sides, and finally 

 imprisoning the prey in 

 a closed chamber of the 

 living substance, together 

 with a drop of water which 

 forms the food - vacuole 

 (Fig. 2, P 1 , P 2 ) in which 

 the prey is digested (p. 192, 

 infra). A very noticeable 

 feature of pseudopodia of 

 all kinds is their adhesive- 

 ness, due to the secretion 

 of a slimy substance at the 

 surface of the ectoplasm. 

 In Difflugia, if the pseudo- 

 podia be touched gently 

 with a glass rod, the slime 

 can be drawn out into 

 threads, like the mucus of 

 a snail (Rhumbler, 34). 

 The adhesive power of the 

 pseudopodia is of service 

 both in adhering to the 

 surface upon which they 

 creep and in the capture 

 of their food. 



The slow -flowing 

 amoebae, such as A. verru- 

 cosa, do not as a rule flow 

 round the body to be in- 

 gested, but draw it into their interior, as if by suction. In this 

 manner A. verrucosa absorbs and devours filamentous algae (Fig. 23), 

 which are " imported " into the interior of the body and there coiled 

 up and digested. Rhumbler has shown that this process can be 

 imitated by drops of fluid ; for instance, a drop of chloroform in water 

 will draw in a thread of shellac and coil it up in its interior in a 

 manner similar to the ingestion of an algal filament by an amoeba. 



end 



FIG. 22. Portion of an Actinosphcerium, magni- 

 fied about 660 linear. ecL, Ectoplasm with 

 larger vacuoles ; end., endoplasm with smaller 

 vacuoles ; N., nucleus ; ps., pseudopodia ; 

 ax., delicate axial rod in the pseudopodia. 

 After Leidy. 



