374 University of California Publications in Zoology [Vol. 20 



within each of the genera and species of the Polymastigina may be 

 considered as established by the numerous investigations of the varied 

 members of this widely distributed group of (mainly) parasitic 

 protozoans. 



The only period in the life of the individual when this morpho- 

 logical constancy in number is modified is the temporary phase of 

 promitosis. During this phase the neuromotor organelles are doubled 

 in number preparatory to mitosis of the nucleus and asexual repro- 

 duction by binary fission of the individual, a process which insures 

 the morphological and numerical constancy of these organelles for 

 the two individuals thus produced. Observed variations within the 

 species in the number of flagella, or of other organelles formed bj' 

 modification of flagella, are attributable to the onset of mitosis, and 

 may be demonstrated to be such by an analysis of the complete mitotic 

 process. 



The importance of recognition of this deduction as a guiding 

 principle in the study of parasitic flagellates and of its practical 

 applications in the diagnosis of human flagellate infections as well 

 as those of other animals is emphasized by Dobell and O'Connor's 

 (1921) treatment of the number of flagella in Trichomonas hominis 

 in their Intestinal Protozoa of Man. In this work Dobell (p. 68, 

 footnote) states that, "In my experience the four-flagellate form 

 (typical Trichomonas) is the commonest in human stools, but the 

 3-flagellate variety is also common. C. D. " They also include the 

 5-flagellate Pentatrichomonas in the synonymy of Trichomonas. The 

 reader is thus led to infer that Trichomonas hominis has three, four, 

 or five flagella. 



Their erroneous treatment of this matter is not only unsound 

 morphologically, but in our judgment will lead to incorrect diagnoses 

 of infections and will deter clinical study of, and therapeutic efforts 

 to cure, human trichomonad infections. It tends to confuse distinct 

 specific entities and to obscure a possible etiological factor in human 

 disease by the as yet pure assumption that the intestinal "Tricho- 

 monas" in man belongs to one species only and that clinical accounts 

 of pathogenic conditions associated with such infections are always 

 to be explained by the further assumption of the concurrence of 

 another unobserved etiological cause. 



No review of the conflicting clinical literature on intestinal 

 trichomoniasis will be attempted here since it has recently been made 

 elsewhere by Haughwout (1918), Kofoid and Swezy (1921), and 



