Some authors believe that a second trichomonad inhabiting man, _Trichomonas intestinalis_, R. Lkt., is identical with _Trichomonas vaginalis_, Donné. Leuckart’s species was based on the discoveries of Marchand (1875) and Zunker (1878), who stated that according to all appearances, and in their opinion, it was the same as _Cercomonas intestinalis_, Lambl, 1875 (_nec_ 1859), which they found in the fæces of patients suffering from intestinal disorders. The organism is described by them as being pear-shaped and 10 µ to 15 µ in length and 3 µ to 4 µ in breadth. The posterior extremity terminated in a point (fig. 17). [Illustration: FIG. 17.--_Trichomonas intestinalis_, Lkt. (After Grassi.)] A row of twelve or more cilia was said to commence at the anterior end and extend over the body. Leuckart stated that this parasite, placed by the two authors in the genus _Cercomonas_, was a _Trichomonas_, and that they mistook the undulating membrane for cilia, and overlooked the flagella. Notwithstanding its striking similarity with _T. vaginalis_, it was said to be distinguishable from that species by differences in the undulating membrane. Lambl’s _C. intestinalis_[38] (of 1875) which corresponds with _C. hominis_, Davaine[39] (1854), is regarded by Leuckart as a true Cercomonad (characterized by a flagellum and the absence of an undulating membrane, see p. 61), and is thus generically distinct from _Trichomonas_. [38] Under the term _Cercomonas intestinalis_, Lambl in different years has described two entirely distinct Flagellata, namely, in 1859 (“Mikr. Unters. d. Darm- Excrete,” _Prag. Vierteljahrsschr. f. prakt. Hlkde._, lxi, p. 51; and Lambl, _A. d. Franz-Josephs-Kinderspitale in Prag_, Prag, 1860, i, p. 360), a form that at the present day is termed _Lamblia intestinalis_; and in 1875 (in the _Russian Medical Report_, No. 33), a species identical with _Cercomonas hominis_, Dav. [39] Davaine, C., “Sur les anim. infus. trouv. dans les selles d. malad. atteints du cholera et d’autr. malad.,” _C. R. Soc. Biol._, 1854, ii, p. 129.