]06 THE AMOEBAE LIVING IN MAN 



I would note here that EndoUmax nana is sometimes parasitized by 

 a micro-organism belonging to the genus Sphaerita Dangeard. The 

 infected amoebae, when alive, are very conspicuous objects, containing 

 one or more spherical morulae of brightly refringent spores of the 

 parasite. The spores are very symmetrically disposed, and at first 

 sight resemble a mass of ingested micrococci enclosed in a food 

 vacuole. Further study of such organisms, however, will show earlier 

 stages in the development of the Sphaerita (cf. fig. 88, PI. V), and dis- 

 closes their true character. The spores stain deeply with ironhaema- 

 toxylin or haemalum (cf. figs. 87, 88), and on being carefully decolorized 

 show very little internal structure (fig. 89). They measure about 0.75/A 

 in diameter, and are consequently very difficult to study. Other stages 

 are correspondingly minute, and I shall not describe them here. The 

 parasite lives in the cytoplasm, and does not attack the nucleus (like the 

 closely related form Nncleopliaga), though the nuclei of many parasitized 

 amoebae appear more or less degenerate. I have not seen Sphaerita 

 within the cysts of E. nana — only in the free amoebae. 



A closely similar form has been described in "Amoeba Umax" by 

 Chatton and Brodsky (1909), to whose work the reader is referred for 

 further details (and literature) concerning these curious parasites of 

 Protozoa. They have been described in several different free-living 

 rhizopods and flagellates, but so far as I am aware have never pre- 

 viously been recorded in any parasitic amoebae. A related parasite — a 

 Nitdeophaga — has, however, been described in the nucleus of Endatnoeba 

 blattae by Mercier (1910). 



I have now seen several E. nana infections in which a considerable 

 proportion of the amoebae were infected with Sphaerita. The one 

 which I was able to follow for the longest time was under observation 

 for about three months, and I always found individuals parasitized by 

 Sphaerita when free forms of E. nana were present in the stools. It 

 thus appears probable that the infection is persistent. It seems, never- 

 theless, to have little effect upon the amoebae as a whole, for most of 

 the Sphaerita infections which I have studied were in persons heavily 

 infected with E. nana, who usually passed large numbers of normal 

 cysts in their faeces. 



I mention this parasite of E. nana here because of its interest and 

 because the infected amoebae have — to my knowledge — already puzzled 

 several people who have seen them. One worker who encountered 

 them mistook the parasitized individuals for a new species of amoeba — 

 the spore morula of Sphaerita being mistaken for a nucleus, whilst the 

 nucleus of the host was overlooked. Other workers have mistaken 

 E. nana individuals, with deeply-stained sporangia, for Dientamoeba 

 and for cells containing masses of micrococci. Sphaerita has such a 

 characteristic appearance in living amoebae that it cannot easily be 

 overlooked, nor can its spores be taken for " nuclei " by a careful 

 observer. 



Cysts. — The cysts of E. nana are very characteristic structures, and 

 contain, when mature, four nuclei. Precystic amoebae contain no food 

 vacuoles, and their cytoplasm is consequently very clear. They are not 

 distinctly smaller than ordinary active forms. Such individuals assume 

 a rounded or oval form, and then secrete a thin cyst wall, which is colour- 

 less and perfectly smooth — as in most other intestinal amoebae. When 

 newly formed, the cyst contains a single nucleus (fig. 25, PI. II), and a 



