ENTAMOEBA COLI 87 



person may pass a stool in which almost every cyst shows these atypical 

 nuclear forms. They are probably the result of some change in environ- 

 ment caused by the diet of the host, or some similar factor. 



The supernucleate and other abnormally nucleate cysts have already 

 been noted by many workers. Casagrandi and BarbagalJo (1897) were 

 probably the first to notice these forms, and they appear to have believed 

 that the number of nuclei in the mature cysts is inconstant. They seem 

 also to have supposed that the nuclear multiplication withui the cyst 

 takes place by a peculiar process — a kind of endogenous budding. 

 Schaudinn (1903) was really the first observer to emphasize the fact that 

 the mature cyst is typically 8-nucleate. According to Smith (1918) some 

 87 per cent, of all E. coli cysts, encountered in random examinations of 

 stools, contain this number of nuclei. It is thus an excellent specific 

 character for purposes of diagnosis. 



Schaudinn (1903), as is well known, described a remarkable process 

 of " autogamy " during the development of the cyst of E. coli. There 

 is not the slightest doubt that he was entirely mistaken in his interpreta- 

 tion — notwithstanding the "confirmations" which have been published 

 by others. As Walker (191 1) and Whitmore (191 1) first pointed out, 

 the development of the cysts of E. coli is perfectly straightforward and 

 simple — just as 1 had previously described it in E. rananivi, and as is 

 probably the case in all Enfamoebae. The observations of Walker and 

 Whitmore have been abundantly confirmed by every competent 

 observer since, and all my own observations are in entire agreement 

 with their interpretation.* 



Glycogen. — E. coli typically contains more abundant glycogen in its 

 cysts than E. histolytica, but it is present only in the earlier stages of 

 development. The glycogen is often formed in the precystic amoebae, 

 before the formation of the cyst wall. This can easily be demonstrated 

 by treating them with iodine solution, when the glycogen shows itself in 

 the form of one or more brown patches of variable size and stained 

 with different degrees of intensity. In the uninucleate cyst the glycogen 

 occupies an area of variable size. Sometimes it appears to be within 

 the protoplasm, and sometimes between the encysted organism and its 

 cyst wall. (Cf. fig. 56, PI. IV.) As already noted, the glycogen is most 

 abundant in binucleate cysts, in which it often occupies the greater part 

 of the available room. In such cysts it appears as a solid mass, with a 

 well-defined edge. It stains deeply in iodine solution, and gives the 

 characteristic reaction with Best's specific carmine stain (fig. 15, PI. I). 

 In stained preparations which have been passed through water, the 

 glycogen, is, of course, removed ; and the area which it occupied is 

 therefore seen as a vacuole (figs. 57-60, PI. IV), usually with an irregular 

 outline. A small amount of glycogen can often be demonstrated in 

 4-nucleate cysts of E. coli ; but its presence in 8-nucleate cysts is 

 extremely rare. It appears to be used up during development from the 

 binucleate to the 8-nucleate stage. Cysts may occasionally be found 

 devoid of glycogen in the early stages of development, but in my expe- 

 rience this is very rare. 



* Although most other workers are very familiar with this fact, I emphasize the 

 point here because Schaudinn's erroneous statements still unfortunately find acceptance 

 with most writers of text-books — both zoological and medical. 



