174 



FAMILIES OF THE AMCEBIDA 



parasitic forms, which have passed through the alimentary canal in the 

 encysted state, are at the height of their free-living existence some time 

 after the escape of the cysts from the body. 



In the order Amoebida are included a number of well-known free- 

 living amoebae, such as Amoeba proteus (Fig. 5) and Amoeba verrucosa 

 (Fig. 87). The majority are uninucleated, but some have tw^o nuclei 

 (A. binucleata), while others have many nuclei (Pelomyxa). In addition 

 to these larger forms, there are others which are smaller, and which are 

 of interest in that some of them are readily cultivated from the fseces of 

 man and animals, owing to the fact that their cysts are able to pass un- 

 harmed through the intestine. Such forms are known as coprozoic amoebae. 



They have frequently been 

 referred to as Amoeba Umax, a 

 name given to an amoeba by 

 Dujardin (1841) which, accord- 

 ing to Dobell and O'Connor 

 (1921), is not now identifiable. 

 Some of the amoebae ascribed 

 to this species have been 

 shown to be the amoeboid 

 phase of the flagellated organ- 

 ism Dirnastigamoeba gruberi 

 mentioned below. Others 

 appear to be true amoeba? 

 which have no flagellate 

 stage. There are many species 

 which are difficult to identify 

 on account of their resemblance to one another. They differ in the character 

 of the cysts they produce, the method of nuclear division, and other details. 

 The order Amoebida may be considered as comprising the following 

 families: 



1. Family: AMCEBIDA Bronn, 1859. — Amoebae which are not able to 

 form flagella. 



2. Family: PARAMCEBiD^ Poche, 1913. — Amoebae which, in addition 

 to a nucleus of the usual type, possess an accessory body (Nebenkorper) 

 which, during division, divides with the nucleus. 



3. Family: dimastigamcebidtE. — Amoebae which in the adult form are 

 able under certain conditions to form two or more flagella, by means of 

 which they progress as flagellates. 



4. Family: RHIZOMASTIGID.E Calkins, 1902. — Amoebae which are pro- 

 vided with a single flagellum during the greater part of the free-living 

 existence. 



Fig. 87. — Amoeba verrucosa ( x 300) 

 Cash, 1905.) 



(After 



