64 THE INVERTEBRATA 



broad pseudopodia, are given to assuming a slug-like shape with one 

 pseudopodium at the foremost end, and have a very simple nucleus 

 with a large karyosome. 



Vahlkampfia, also found in foul infusions, is a typical member of 

 the Umax group. 



Amoeba (Fig. 54). Typical amoebae, with numerous pseudo- 

 podia; contractile vacuole; and no flagellate phase. Various species. 

 The true A.proteus is the largest of the common Amoebae^ has a lens- 



t^ 



Fig. 53. Naegleria bistadialis, x 800. Partly after Kiihn, in Doflein. A, Amoe- 

 boid condition. B, Transition to flagellate condition. C, Flagellate condition. 

 con.vac. contractile vacuole; rh. rhizoplast. 



shaped nucleus and longitudinal ridges on the ectoplasm, forms 

 spores endogenously in the unencysted condition, and is not a diatom 

 feeder. 



Entamoeba (Figs. 55, 56). Parasitic amoebae; without contractile 

 vacuole. Reproduction during most of the life history is by binary 

 fission. Finally encystment takes place and in the cyst the nucleus 

 divides several times. The cysts pass out of the host and infect a new 

 individual, in which they are dissolved and set free their contents, 



