DOUBTFUL AMOEBOID ORGANISMS 137 



described an " amoeba " from the intestine of man and named it 

 " E. wididans." From his description and figures there can be no 

 doubt that these " amoebae " — which possessed an undulating membrane 

 — were really degenerate forms of Trichomonas hoiiiitiis, with which his 

 patient was said to be also infected. This has already been pointed 

 out by a number of workers (Wenyon (1913), Hartmann (1913), etc.). 

 The non-flagellate, amoeboid, degenerating forms of various species 

 of Trichomonas are now familiar to all workers who have studied these 

 organisms. It may be noted that they were probably first mistaken for 

 amoebae in man by Lambl (i860) ; and that they were seen and first 

 correctly identified as degenerating flagellates* by Cunningham (1871). 

 Since then they have many times been mistaken for amoebae. 



" Craigia." — Craig (1906) has described a remarkable organism to 

 which he originally gave the name Paranioebn hominis — believing it to 

 be similar to the marine Paramoeba eilhardi Schaudinn.t Subsequently, 

 it was placed in the new genus Craigia by Calkins (1912). The organism 

 is said to live in the intestine, to be pathogenic, and to possess both 

 amoeboid and fiageliate stages in its life-history. The amoeboid forms 

 apparently resemble E. coli and measure 10-25 M •" diameter. They 

 form multinucleate cysts which liberate broods of flagellates " 10-20 /t 

 in diameter." Although Craig has published two accounts of this 

 organism {1906, 1910), and made frequent reference to it in other works, 

 he has never advanced adequate evidence for its existence. To prove 

 that an organism such as he postulates really exists, requires further 

 evidence, — evidence, moreover, of quite a different order from anything 

 which he has yet been able to adduce. There is, nevertheless, abundant 

 evidence in Craig's works that he was not, when he wrote, sufficiently 

 familiar with the common intestinal amoebae and flagellates of man to 

 be able to distinguish a new organism of the type described — supposing, 

 it to exist. Obvious sources of error and confusion were not excluded ;. 

 and in the absence of all essential mformation concerning the cytology 

 of " Craigia," I am unable to accept his conclusions. 



So far as I am aware " Craigia " has been found subsequently by only 

 one other worker — Barlow (1915). This writer not only " confirmed "^ 

 Craig's observations but extended them by discovering a new species. 

 According to him, there are really two species of "Craigia," — C. hominis 

 and C. migrans. His descriptions of both, however, serve only to 

 confirm my suspicions that all these organisms are in reality a mixture 

 of other and more familiar species of amoebae and flagellates. I have 

 never found any organism which resembles Craigia : and until it has 

 been vouched for by some independent and competent protozoologist — 

 familiar with all the intestinal protozoa of man, and in possession of first- 

 rate preparations of all the stages described — I am unable to believe in 

 its existence. The name Craigia should therefore, in my opinion, be 

 regarded as a nomen nudum, or as a partial synonym of at least two other 



* Cunningham, however, called the organism " Cercomonad A," and was not aware 

 that it was a Trichomonas. 



t I am inclined to believe that P. eilhardi is itself probably a fictitious organism, 

 formed by combination of a rhizopod with the swarmers of an alga. I find Schaudinn's- 

 account of it far from convincing. 



