ENTAMOEBA HISTOLYTICA 53 



As regards the race called "3 " in this table, it should be added that 

 Wenyon and O'Connor (1917) have studied one somewhat similar (their 

 case " Kettlewell ") : and I have also seen at least one similar infection, 

 in which the cysts ranged round a mean of about 10 /x.* The race 

 called " 6 " in the table, is absent from Ujihara's series. It undoubtedly 

 exists, however, as I have studied several cases ; and Wenyon and 

 O'Connor (1917) have recorded a case of the same type (case " Healy "), 

 with large-sized cysts reaching 18 fi in diameter. The large cysts of 

 these strains of E, histolytica are sometimes attributed to E. coli. I know 

 of several actual instances where this mistake has been made in the 

 laboratory, 



James (1914) found cysts of E. histolytica measuring 7-10 fi in 

 diameter, and referred them to their proper species.f Woodcock and 

 Penfold (1916) again described small-sized cysts of E. histolytica, but 

 proposed to call them provisionally " E. ininuta." This was an unfortu- 

 nate application of the name originally proposed by Elmassian (1909) ; 

 and although Woodcock (1917) still adheres to this nomenclature, there 

 is clearly no justification for it.:J: 



Swellengrebel (1917) has described small cysts of E. histolytica, but 

 attributed them to the flagellate Chilomastix mesnili. Kuenen and 

 Swellengrebel (19 17) in the same year again described them, but regarded 

 them as the cysts of a new species of Entamoeba, which they proposed 

 to call E. tetmis. It may be noted as a curiosity, however, that Kuenen 

 and Swellengrebel (191 3) had previously referred Prowazek's E. hart- 

 nianni, which was the same thing — i.e., a race of E. histolytica producing 

 small cysts — to " E. tetragena," which is their name for E. histolytica. 

 They have given no reasons for these inconsistent statements. Brug 

 (1917) has also found the small cysts of E. histolytica, and has also 

 regarded them as belonging to a new species, for which he proposed 

 the name E. minutissivia. Later, however, Brug (1918) withdrew this 

 name in favour of that of Kuenen and Swellengrebel. It is thus diffi- 

 cult to understand what the Dutch workers' present views really are 

 about the strains of E. histolytica which produce small cysts ; and it is 

 possible that they will undergo still further changes when they have 

 studied the publications of others. At present they appear to be 

 unaware of the large amount of work which has been done on this 

 subject by English investigators. 



Mathis and Mercier (1917^) are unwilling to believe in the existence 

 of the strains of E. histolytica with cysts of different sizes. Their 

 doubts were expressed, however, before the appearance of my full paper 

 on the subject (Dobell and Jepps, 1918). Various objections which 

 they raised have there been answered, though some of their criticisms 

 appear to me irrelevant. It may be noted that they regard all cysts 

 of E. histolytica with diameters of less than 10 fi as "abnormalities" — 

 a view which is certainly untenable. It may be noted further, as 



• Vide Dobell and Jepps (1918), p. 540. 



t Called by him E. tetraoena. James appears to have regarded the small cysts as 

 abnormal, for he says " probably some circumstance of environment was responsible 

 for their condition" (1914, p. 187). This hypothesis can hardly be maintained now 

 that it has been proved that two strains — a small and a large — may exist in the same 

 host simultaneously (Dobell and Jepps, 1918). 



% Cf. Dobell and Jepps (1917, 1918). 



