268 ' WALKER. 



of the, host (Compare figs. 1 to 8 with figs. 9 to IG). 1 believe, the 

 characters of this type of amoeboid organism are sufiiciently distinct from 

 the Amcsba type to justify the establishment of the new genus, Entamceha, 

 by Casagrande and Barbagallo (1897) and its adoption by Schaudinn 

 (1903). This genus should include the parasitic amoebae of man and also 

 the parasitic amcebge that have been described in certain lower animals, 

 namely: Entamceba ranarum (Grassi) Dobell, 1908, in the frog, Enta- 

 mosba testudinis Hartmann, 1910, in the turtle. Entamoeba muris (Grassi, 

 1881) Wenyon, 1907, in the mouse, and Entamoeba nutalli Castellani, 

 1908, in the monkey. 



What, then, is the significance of the species of the genus Amoeba cul- 

 tivable from the intestinal tract of man and other animals ? 



These cultivable amcebfe might be considered parasitic entamoebse that 

 had undergone modification by their growth on artificial culture media. 

 It seems possible that such a change in environment might modify some 

 of the less constant morphologic characters of these organisms, such as 

 size, shape, number of pseud opods, extent of the ectoplasm, and granula- 

 tion or vacuolization of the entoplasm. ; but that it could cause a complete 

 reorganization of the structure of the nucleus, develope de novo such a 

 constant organelle as a contractile vacuole, or profoundly modify the 

 life-cycle of the organism appears doubtful. Moreover, that the supposed 

 modification resulting from cultivation on artificial media should in- 

 variably take the form of a change from the characters of the genus 

 Entamaiba to those of the genus Amoeba is, to say the least, improbable. 



It might be claimed that, owing to some fault in my technique, I had 

 failed to cultivate the parasitic entamoebse. Among my cultures are 

 four isolated by as many different investigators, other than myself, two 

 of which are from cases of amoebic dysentery and one of these isolated 

 by Musgrave and Clegg (1904) ; all of these cultures, like my own, are 

 of the Amoiba type. Werner (1908) failed to cultivate entamoebas from 

 cases of amoebic dysentery. Dobell (1908) and Weryon (1907) also 

 were unable to cultivate on artificial media the entamoebse which they 

 found in the intestines of lower animals. An examination of the de- 

 scriptions and illustrations of amoeboid organisms cultivated by difilerent 

 authors shows in every case organisms not of the Entamoeba but of the 

 Amoeba type. 



There still remains the possibility that the cultivable amoebse, as well 

 as the non-cultivable entamoebae, are parasitic in the intestinal tract of 

 man. Since, however, organisms of the Amoeba type are not found in 

 the microscopic examination of fresh or stained preparations of fseces, 

 liver-abscess pus, or in sections of liver or intestine, it seems probably 

 that the amoeboid organisms cultivated by Musgrave and Clegg (1904), 

 Lesage (1905, 1908), Gauduchea (1908), andNoc (1909) from the 

 intestine and liver abscesses of man, and by myself (Walker 1908) from 



