52 



PROTOZOOLOGY 



the often-quoted experiment of Verworn, a Umax amoeba changed 

 into a radiosa amoeba upon addition of potassium hydroxide to the 

 water (Fig. 7). Mast has recently shown that when Amoeba proteus 

 or A . dubia was transferred from a salt medium into pure water, the 

 amoeba produced radiating pseudopodia, and when transferred 

 back to a salt medium, it changed into monopodal form, which 

 change he was inclined to attribute to the difference in the water 

 contents of the amoeba. In some cases during and after certain in- 

 ternal changes, an amoeba may show conspicuous differences in 



Fig. 7. Form-change in a limax-amoeba (Verworn). a, b, contracted 

 forms; c, individual showing typical form; d-f, radiosa-forms, after ad- 

 dition of KOH solution to the water. 



pseudopodia (Neresheimer). As was stated before, pseudopodia occur 

 widely in forms which are placed under classes other than Sarcodina 

 during a part of their life-cycle. Care, therefore, should be exer- 

 cised in using them for taxonomic consideration of the Protozoa. 

 Flagella. The flagellum is a filamentous extension of the cytoplasm 

 and is ordinarily extremely hue and highly vibratile, so that it is 

 difficult to recognize it distinctly in life under the microscope. It is 

 most clearly observed under a darkfield or phase microscope. Lugol's 

 solution usually makes it more easily visible, though the organism is 

 killed. In a small number of species, the flagellum can be seen in life 

 under an ordinary microscope as a long filament, as for example in 



