244 FAMILY: AMCEBID^ 



The free forms of /. hutschlii are intermediate in size between those 

 of Entamoeba coli and Endolimax nana (Fig. 114, 1-4). They are 9 

 to 13 microns in diameter, but larger forms up to 20 microns and 

 smaller ones down to 5 microns in diameter have been seen. Kuenen 

 and Swellengrebel (1917), who first described the amoeba, gave 10 to 

 12 microns as the measurement, while Brug (1921) gives 7 to 20 microns. 

 Taliaferro and Becker (1922) state that the largest form seen by them 

 measured 20 by 15 microns. There is no marked distinction of ecto- 

 plasm and endoplasm, and the movements are sluggish, like those of 

 E. coli. The endoplasm contains numerous food vacuoles, which include 

 various bacteria. According to Brug, the amoeba feeds only on very 

 small particles, and does not ingest large bodies, as E. coli often does. In 

 the living amoeba the nucleus can hardly be detected, a feature which 

 serves to distinguish it from E. coli, the nucleus of which is nearly always 

 distinct. As first pointed out by Dobell (1919), and later by Taliaferro 

 and Becker (1922), it is the structure of the nucleus which is the most 

 characteristic feature of the free forms. As seen in stained specimens, 

 it is a vesicular structure with a diameter of 2 to 3-5 microns. There is 

 a large karyosome, which has a diameter of about a third to a half of that 

 of the nucleus itself. The membrane of the nucleus is well developed, 

 while the karyosome is surrounded by a layer of globules composed of 

 a substance which does not retain the stain as long as the karyosome, and 

 is thus probably not of chromatin nature. These globules sometimes 

 indent the karyosome, and give it a stellate appearance, while the septa 

 between the globules may produce the impression of a series of radiating 

 fibres connecting the karyosome to the nuclear membrane. Multiplication 

 by binary fission has been noted by Eodenhuis (1919), but the details of 

 the process have not been described. Amoebse with cytoplasm devoid of 

 good vacuoles, and with or without a glycogenic body, are probably pre- 

 cystic forms (Fig. 114, 5). 



The cysts of /. hiitsclilii were first seen by the writer in 1906 in the 

 Sudan, and were not seen again till 1915, when a description was given. 

 They appear to be much more frequently encountered in stools than the 

 free amoebae, and as very heavy infections sometimes occur without it being 

 possible to discover any amoebae, the writer considered that the cysts might 

 be vegetable organisms. This view seemed*to receive support from the fact 

 that filaments grew out from certain cysts when kept under observation in 

 saline solution. It seems clear from what is known now that those cysts 

 which produced filaments were really of another nature, and not the cysts 

 of the amoebaj. The writer has on several occasions kept cysts which were 

 not identifiable, and has seen them produce long branching filaments across 

 the preparations, a clear indication that they were spores of fungi. 



