l6 THE AMOEBAE LIVING IN MAN 



same genus — whatever that may be. Moreover, the amoeba Hving in 

 the mouth of man (£. gingivalis) cannot at present be distinguished 

 generically from these two forms. But should these three species be 

 placed in the same genus as the amoeba of the cockroach ? Should 

 they, in other words, be put in the genus Endamoeba Leidy ? 



At the present moment this question cannot be answered con- 

 clusively. Chatton and Lalung-Bonnaire (191 2) and Alexeieff (191 2) 

 have answered it in the negative, basing their views on the differences 

 in development described by Mercier (1910) in the parasite of the 

 cockroach. It therefore appeared to them necessary to introduce a new 

 generic name for the amoebae of the type of E. coli, because these 

 workers — and all others, apparently — consider that " Endamoeba " and 

 " Entamoeba " are mere variant spellings of the same name. Chatton 

 and Lalung-Bonnaire (1912) accordingly proposed the new generic 

 name Loscliia, whilst Alexeieff (191 2) proposed the new name Prod- 

 amoeba. Alexeieff's paper was published about a month after that of 

 Chatton and Lalung-Bonnaire ; and consequently, when this was 

 pointed out by Chatton (191 2), he withdrew his name later (Alexeieff, 

 1912 a), as a synonym of Loscliia. It would thus appear, at first sight, 

 that the amoeba of the cockroach should be placed in the genus 

 Endamoeba Leidy, whilst the three best-known amoebae of man (E. coli, 

 E. histolytica, E. gingivalis) should be placed in the genus Loscliia. 



There are, however, two real difficulties in the way of accepting this 

 solution. First, it is by no means certain, at the present moment, that 

 the amoeba of the cockroach and the amoebae of the E. coli type are 

 generically distinct. The distinction was drawn at a time when these 

 amoebae were believed to possess quite dissimilar life-histories. Accord- 

 ing to Mercier (1910), E. blattae has a sexual phase at the beginning of 

 its life-cycle. The cysts liberate broods of large or small amoeboid 

 gametes which conjugate in pairs heterogamously. The previous 

 development within the cysts is simply a process of straightforward 

 nuclear division. On the other hand, according to Schaudinn (1903) 

 and Hartmann (1908) respectively, E. coli and E. histolytica (then called 

 E. tetragena) display a process of autogamy within their cysts; so that 

 a later gamete-formation and conjugation, like those of E. blattae, 

 appeared to be excluded from their development. At the present 

 moment, however, the position is very different. We now know, since 

 the work of Walker (191 1) and others — which agreed with my original 

 observations (1908, 1909) on the closely related amoeba of the frog — 

 that there is no autogamy in the cysts of E. coli, E. histolytica, or any 

 of their congeners. The development within the cyst is a straight- 

 forward process of nuclear division, like that described by Mercier and 

 others in E. blattae. Furthermore, Mercier's account of the sexual 

 process in this species has not yet been confirmed, and the corres- 

 ponding stages in £. coli and E. histolytica have never been studied. 

 vVhether they are alike or different in this respect has therefore still 

 to be determined ; and upon this determination the decision as to 

 whether they should be placed in the same or m different genera will 

 largely depend. 



A second difficulty is this. Liihe (1908), believing Schaudinn's (1903) 

 incorrect account of the development of E. histolytica to be true, pointed 

 out that this parasite could not be placed in the same genus with E. coli 

 and related forms. He therefore proposed the new genus Poncramoeba 



