ENTAMOEBA GINGIVALIS 97 



its food mainly, taking in by osmosis the fluids of leucocytes or other 

 media on which it rests." It is difHcult to reconcile this view with the 

 fact that the amoeba is frequently filled with what are obviously the 

 remains of nuclei of some sort, and also with the same worker's earlier 

 statement that the amoeba " can load up with a great cargo of cells and 

 tartar." The most astonishing view, however, is that expressed by 

 Craig (1916), who conjectures — for no apparent reason — that the inclu- 

 sions in £. giiigivalis are " some species of protozoan organism." 



As I liave already noted, 1 have never seen red corpuscles in 

 £. giiigivalis ; but I am not prepared to deny that they are ever ingested 

 by this species, in view of the statements of Smith and Barrett, Goodrich 

 and Moseley, and others. That they are not ingested as frequently as 

 the former authors believe, however, there seems good reason to suppose. 

 Most of the inclusions are undoubtedly the lemains of nuclei, either of 

 salivary corpuscles or of other leucocytes or cells. I believe polymor- 

 phonuclear leucocytes are occasionally ingested. The organism figured 

 in PI. V, fig. 93, contains, I believe, the remains of one. Apart from 

 these nuclear residues, £. giiigivalis also ingests bacteria, which are 

 usually present in large numbers in its vacuoles. These have been seen 

 and described by Prowazek (1904), Smith and Barrett (1915), Goodey 

 and Wellings (1916), and most other observers. Nowlin (1917 a) states 

 that she has observed the living amoebae ingesting bacteria. I have not 

 been able to watch this process myself, though it must occur frequently 

 when the animal is in its normal environment. 



E. gingivalis probably reproduces by division into two, but I have 

 observed no stages in the process. Prowazek (1904) mentions simple 

 fission as its chief mode of multiplication, and a figure of his, showing 

 an amoeba with a "dividing nucleus," has been several times repro- 

 duced (cf. Hartmann and Prowazek (1907) p. 316, Hartmann (1913) 

 p. 641, etc.) and interpreted in various ways. Originally it was said to 

 show one nucleus dividing inside another ; later, to be a single nucleus 

 undergoing " promitosis." Stages in a process of mitosis are referred to 

 by Chiavaro (1914), but not clearly described. A late stage in division is 

 figured by Goodey and Wellings (1916), but they found no earlier stages. 

 Goodrich and Moseley {1916) state that reproduction is effected by 

 " binary fission," but the process does not appear to have been observed 

 in detail. Nowlin (1917) records a "mitosis" in this organism, but 

 "gives highly unconvincing figures. She also believes that "budding" 

 or "multiple fission" takes place, "merozoites" being formed to the 

 number of " 8 or 9 to more than a dozen." From the description and 

 figures it appears probable that these were cellular elements of some 

 sort from the mouth, and not amoebae. Other authors mention division, 

 but no one has yet described it properly. 



Cysts of E. giiigivalis have been described by several workers. Smith 

 and Barrett (1915) state that they " have found 'dauer' cysts, but thus 

 far no reproductive cysts" — whatever that may mean. No descriptions 

 are given. Craig (1916) describes both " cysts " and " precystic amoebae." 

 The former are said to measure 8-iO/Lt in diameter, and to be uninucleate. 

 " Larger cysts are sometimes observed," but all sizes are said to 

 be very rare. According to Goodrich and Moseley (1916) Craig's 

 cysts probably belonged to " limax " amoebae, which they believe to 

 occur occasionally in the mouth. Craig truly says of the "cysts" 

 previously found byChiavaro(i9i4) that they are "far from convincing." 



7 



