144 SOME MINUTE ANIMAL PARASITES 



and being used for progression and food capture. The 

 body shows, at any rate at some phase of its exist- 

 ence, a distinct outer layer, or ectoplasm (Fig. i, ect.}* 

 and a more granular inner layer, the endoplasm 

 (Fig. i, end.}. Pseudopodia at first are purely ecto- 

 plasmic, and it is only by degrees that the endoplasm 

 flows into them. The number of pseudopodia varies 

 greatly. A mceba proteus from pond- water shows several 

 pseudopodia at a time (Fig. i,ps.). The small amoeba, 

 belonging to the Umax group, sometimes found in 

 household water-taps, has a sluglike appearance, for 

 it usually protrudes one pseudopodium at a time. 

 Amoebae from the alimentary canals of higher animals 

 may show one or many pseudopodia according to 

 their condition. The search for food on the part of 

 an amoeba, as well as the desire for movement, en- 

 tails the protrusion of several pseudopodia. 



The pseudopodia vary greatly in shape. Two main 

 types, however, can be distinguished. The first is 

 broad and club-shaped, or lobose ; the second is long, 

 narrow, and threadlike. It is usual for one type only 

 to be produced at any one given time, though grada- 

 tions between the two types necessarily occur. 



The endoplasm is often very granular, and may 

 include various non-living enclosures, such as crystal- 

 loid substance, waste material from food and colour- 

 ing matter, as well as actual food particles themselves. 

 The food is enclosed in thin films of liquid, and forms 

 food vacuoles. The vacuoles contain some form of 

 digestive ferment, and the amoeba shows the most 

 primitive form of digestion known. Further, in 



* See p. 2. 



