1920] Kofoid: Nomenclature of Human Intestinal Flagellates 151 



Chilomastix davainei (Moquin-Tandon) 



The question now arises as to what flagellates Davaine (1854:, 1860) 

 really had as the basis of his description of Cercom,onus hominis vars. 

 A and B. After considerable experience in the examination of living 

 human intestinal flagellates from fresh stools and cultures thereof 

 (except Giardia), and a critical reading of Davaine 's earlier (1854) 

 and later (1860) accounts of the organisms discovered by him, we 

 conclude that (1) Davaine had two different flagellates, his vars. A 

 and B. This rests on his own decision, the accumulated statistical 

 evidence of recent years, and the contrasts in his descriptions and 

 figures; (2) the larger form, his var. A, is Chilomastix, and the smaller 

 one. Trichomonas. This decision is supported by the relative sizes of 

 Chilomastix, 19.6 (13-24)ja and Trichomonas, 5-15/^. Chilumaslix 

 sometimes has the dimensions as small as those given by Davaine. A 

 second and most conclusive evidence is Davaine 's (186G, p. vi, not 

 in 1854) statement "trait longitudinal vers I'extremite anterieure, 

 donnant 1 'apparence d 'un orifice buccal ? ; ". Chilomastix is the only 

 human flagellate with well-defined, elongated cytostome except 

 Emiadomonas, which is much smaller and apparently very rare. This 

 cytostome serves todaj^ as the best available criterion for the certain 

 identification of Chilomastix in both free and encysted stages. The 

 cytostome of Trichomonas is not elongated nor so bordered by a 

 cytostomal rim as to be easily seen as is that of Chilomastix. The 

 tapering posterior end (extremite amincie) is also a distinguishing 

 characteristic. Davaine 's (1860) figures of his form may be har- 

 monized without difficulty, save in the matter of the number of 

 flagella, with our present knowledge of Chilomastix. 



We therefore conclude that Davaine's (1860) Cercomonas hominis 

 var. A is the organism later described by Wenyon (1910) as Macro- 

 stoma mesnili and now generally called Chilomastix mesnili. A survey 

 of the literature indicates that Brumpt (1912) and Chalmers and 

 Pekkola (1917), investigators of Chilomastix, all agree that Cerco- 

 monas hominis var. A Davaine is the same organism as Chilomastix 

 mesnili, though Brumpt later (1913) places an interrogation mark 

 after the synonym and Chalmers and Pekkola quote Ccrcomonas 

 hominis as a synonym pro parte without noting his varieties. 



Since Davaine's Cercomoneis hominis is a complex of two species, 

 the withdrawal of either one of these under a new name leaves hominis 

 as the residual name for the species not withdrawn. This withdrawal 



