ENDOLIMAX NANA I05 



the usual " clear zone," sometimes traversed by radiating strands of 

 "linin" (fig. 21). I have not been able to convince myself of the 

 existence of any " peripheral chromatin " in the clear zone. 



The nuclear appearances just described arc those characteristic of 

 this organism immediately after its discharge from the human body. 

 If the amoebae are kept for some time subsequently, so that many of 

 them degenerate and die, they show a considerable difference in nuclear 

 structure. The karyosome segments run together into a more or less 

 homogeneous mass, which then generally comes in contact with the 

 nuclear membrane at one pole of the nucleus. The latter then has the 

 appearance of a signet ring — the karyosome representing the signet. Such 

 amoebae are certainly abnormal, as anybody can convince himself by 

 examining a good series of stained preparations made from a stool con- 

 taining large numbers of amoebae and fixed at different intervals of time 

 after it was passed. It will then be found that it is only in the freshest 

 samples that the true nuclear structure of £. nana can be seen. 



The typically irregular forms of karyosome in this species were noted 

 by Wenyon and O'Connor (1917). Swellengrebel and Mangkoe Winoto 

 (1917) and Kuenen and Swellengrebel (1917), however, appear to regard 

 a spherical karyosome as the normal form — apparently because they did 

 not study sufficiently fresh material. Had they done so, they could 

 hardly have considered— as they do, apparently — that E. nana is a kind 

 of " Umax amoeba." From all such organisms it is readily distinguish- 

 able by its karyosome alone. James (1914) shows an organism, which I 

 believe to be E. nana, containing a nucleus with an irregular karyosome 

 (see his fig. 117, PI. xv). He probably saw the usual forms of the karyo- 

 some in this species, but mistook them for stages in division : for he says 

 (J'imes, 1914, p. 198) he saw " many organisms in various stages of 

 division " in his preparations. But even in the freshest preparations 

 division stages are excessively rare ; and unfortunately he does not 

 describe or figure his dividing forms. 



Endoliniax nana doubtless multiplies, like other amoebae, by division 

 into two. I have not yet succeeded in finding more than a very few 

 organisms which may show stages in nuclear division, and I am 

 therefore unable to describe the process of fission at present. I would 

 add that the various forms of karyosome encountered in individuals of 

 this species appear to bear no relation to nuclear division : and although 

 the different forms can be easily arranged in series with one another, 

 there is at present no possible means of ascertaining whether such a 

 series corresponds with a serial or cyclical change which takes place 

 in the nucleus of one and the same organism during its life. 



I have not succeeded in cultivating E. nana in any medium, — nor 

 has any other worker, so far as I can ascertain. I may note, however, 

 that I have cultivated free-living amoebae ("Umax amoebae") from 

 stools which originally contained E. nana, and I believe that other 

 observers (such as Gauducheau, Noc, and Lesage) may have done the 

 same : which may partly account for their belief that they had culti- 

 vated amoebae which normally live in man. 



The habitat of E. nana is the human intestine, but the exact site of 

 infection in the bowel is still in doubt. There are some reasons for 

 believing that it may live in the small intestine (cf. Dobell and Jepps, 

 1917), but this has still to be verified. That it lives in the contents 

 of the intestine, and is not a tissue parasite, is, however, certain. 



