ENTAMOEBA COLI 89 



nuclei. That these filaments are really chroiiiatoid bodies, and not 

 inclusions of some other sort, I think there can be no doubt : for stages 

 intermediate (fig. 64) between the typical filamentar form (fig. 65) and 

 the more usual acicular sheaves (fig. 63) are not difficult to find. These 

 cysts with filamentar chromatoid bodies appear to be those which 

 Prowazek (191 1) described in his new species " Entauweba ivilliaiiisi."'- 

 They were also, apparentl}', included in " E. brasilieiisis" by Aragao 

 (1912, 1914), and have been seen and figured by other workers. 



According to Malins Smith (1918) chromatoid bodies occur in 5*5 per 

 cent of the cysts of E. colL This figure, however, is certainly too low ; 

 for it was arrived at by considering only those cysts which contain 

 conspicuous chromatoids. All those with small chromatoid bodies, only 

 demonstrable with certainty in carefully stained specimens, were left out 

 of account. 



Mathis and Mercier (1917 a, b, d alibi), apparently alone among recent 

 workers, deny that chromatoid bodies ever occur in the cysts of E. colt. 

 So far as I understand their views, they regard the deeply stained bodies 

 in the cysts of this species as artifacts, formed by a deposition of stain 

 (iron-haematoxylin) in folds of the cyst wall or in the protoplasm. It 

 is easy to convince oneself that this interpretation is incorrect. The 

 chromatoid bodies are easily visible in living cysts, and readily stained 

 by carmine, haemalum, and other progressive methods. I can only 

 suppose that these authors have devoted too little attention to the study 

 of living cysts, and too much to iron-haematoxylin preparations. From 

 their more recent papers (Mathis and Mercier, 1917 c,/) I gather that 

 they now admit that chromatoid bodies are sometimes present in E. coli 

 cysts, though they call them by a different name from that which they 

 give to the chromatoids of E. histolytica. \ This seems to me an attempt 

 to fix an arbitrary verbal distinction where none exists in nature. 



The chromatoid bodies of E. coli are probably formed in the same 

 manner, and subserve the same functions, as those of E. histolytica. 

 Their origin in the cysts is equally difficult to determine, and at present 

 doubtful. I have never seen them in the precystic amoebae of this 

 species, though they are possibly formed before encystation occasionally,, 

 as in E. histolytica. This is a very difficult point to determine, owing to 

 the great similarity of the precystic amoebae of both species, and the 

 frequency of mixed infections. 



Chromatoid bodies were probably first noted in the cysts of E. coli by 

 Grassi (1879), They were seen later by Casagrandi and Barbagallo- 

 (1897)4 who regarded them as a sort of reserve material ("alimento 



• Prowazek (1911, I9i2)gives as a further character of this "species" the occurrence 

 of cysts containing 10 or 14 — 15 nuclei. These, as already noted, sometimes occur in 

 ordinary E. coli infections. It should be noted that Prowazek also stated that his 

 " £". williamsi'" occurred in company with E. coli, 



t They now call the chromatoids of E. histolytica " bdtonnets siderophiles," and 

 those of E. coli "plages siderophiles"; which clearly shows the undue importance 

 which they give to the iron-haematoxylin method. Cf. Mathis and Mercier (1917 e). 

 Chatton (1917, 1918 a) has already criticized their statements, and I have elsewhere 

 pointed out the incorrectness of their observations in this respect (Dobell and Jepps, 

 1917). 



X Their figure 18 shows, in my opinion, a cyst of E. coli containing a chromatoid 

 body. Viereck (1907), however, regarded it as a cyst of E. histolytica — falling, I 

 believe, into the very conmion error of attributing every cyst which contains chroma- 

 toid bodies to this species. 



