OF THE ALIMENTARY TRACT 31 



organisms which typically move and feed by the 

 means of pseudopodia, that is by currents in their 

 cytoplasm which may stream to a local part of the 

 surface producing a finger-like projection, or may 

 flow as a whole in one direction, leading to progres- 

 sive locomotion. 



The cytoplasm of the body shows division into a 

 peripheral ectoplasm of apparently uniform consis- 

 tency, and an inner endoplasm of more or less alveo- 

 lated, vacuolated, or granular appearance. The ecto- 

 plasm is particularly specialized for the formation of 

 pseudopodia, in other words conforms to and fulfills 

 the purpose of the peripheral apparatus of all animals, 

 i.e. locomotion, feeding, excretion, and maintaining 

 contact with the external environment. In the endo- 

 plasm occur the nucleus, the digestive cavities, etc., 

 in other w^ords the interior apparatus of the animal 

 body, the "vital organs" and systems. 



This division into ectoplasm and endoplasm varies 

 among the genera, between species, and with in- 

 dividuals. 



The nucleus is usually single and varies among the 

 species to give characteristics commonly depended 

 upon for differentiation. 



All but one of the species found in man are known 

 to undergo encystment. The amoeba of the mouth, 

 Endainoeha giyigivalis, apparently does not encyst. 

 It has no need of a phase for protection against ex- 

 ternal exposure since it naturally would be trans- 

 mitted directly from person to person by contact. 



