260 FAMILY: PARAMCEBID^ 



The figures given for Hadra Prison show the results obtained by 

 single examinations of natives of the country. In the case of E. nana, 

 the low figure is explained by the fact that the examinations were largely 

 made before it was recognized that E. nana was a parasitic amoeba. 



During the war a large number of examinations were made of healthy 

 persons in the British Isles, and though isolated cases of E. histolytica 

 infection in individuals who had never left the country had already been 

 recorded by Marshall, D. G. (1912), the writer (1916) and others, it was 

 Yorke and his collaborators (1917) who first showed that amoebic infections 

 were quite common amongst the indigenous population. Dobell (1921) 

 has examined the records of several observers, and after allowing for 

 the errors of the single examination concludes that the percentages 

 of infections to be found amongst the artisan population are as follows : 

 E. histolytica, 7 to 10; E. coli, 36 to 54; E. nana, 9 to 13; /. biitschlii, 

 0-5 to 0-75. 



Boeck (1921) has published the results of examination of eighty-three 

 industrial school children in America. Each case was examined, on an 

 average, 5*3 times. He gives the following figures of percentages: E. histo- 

 lytica, 10-8; E. coli, 49-3; E. nana, 6-0; /. biitschlii, 1*2. Similar records 

 have been published from other parts of the world. 



2. Family: PARAMCEBiDiE Poche, 1913. 

 This family includes the single genus Paratnosba, which was created 

 by Schaudinn (1896) for a marine amoeba, Paramceba eilhardi, which 

 possessed, in addition to its nucleus, an accessory body (Nebenkorper). 

 Both the nucleus and the " Nebenkorper " divided during division of the 

 amoeba. Janicki (1912) pointed out that two amoebae {A. pigmentifera 

 and A. chcBtognathi) which Grassi (1882) had discovered in the body cavity 

 of the small marine worms of the genera Spadilla and Sagitta belonged to 

 this genus (Fig. 119). During division of the amoeba the nucleus divides 

 by mitosis, while the " Nebenkorper " divides by simple elongation and 

 constriction. Small elongate flagellates, each with a single flagellum, are 

 produced. These, after multiplying by division, conjugate and give rise 

 to zygotes which become the amoebae. 



3. Family: dimastigamcebidte. 

 This family includes amoebae which are able, under certain conditions, 

 to develop flagella and behave as flagellates. When they occur in faeces 

 or are cultivated on the surface of agar plates they live and repro- 

 duce as amoebae, but if brought into liquid media they quickly grow 

 flagella and swim about for some hours, after which the flagella are lost 

 and the amoeboid phase is resumed. One of these amoebae was isolated 



