The size varies from 6 µ to 32 µ. Ectoplasm is always present; the endoplasm contains numerous food-vacuoles. The nucleus is vesicular, with a greenish tinted membrane which is poor in chromatin. The size of the nucleus is from 1·5 µ to 4·5 µ. A contractile vacuole is not visible. The pseudopodium is broad. It was discovered in the mouths of persons with dental caries at Rovigno and also at Trieste, being most easily found in dense masses of leucocytes, also among leptothrix and spirochæte clusters. It can be easily distinguished from leucocytes by more intense staining with neutral red. Multiplication proceeds by fission. Transmission may take place through the small spherical cysts. This species (fig. 10) has since been observed in Berlin, and is also occasionally found in carcinoma of various regions of the oral cavity. (Leyden and Löwenthal, 1905). [Illustration: FIG. 10.--_Entamœba buccalis_, Prow. _a_-_d_, the same specimen observed during five minutes. × 1,000. _e_, amœba fixed and stained with iron-hæmatoxylin. × 1,500. (After Leyden and Löwenthal.)] _Entamœba buccalis_, Prow., is said to be allied to a protozoön which A. Tietze has found either encysted or free in the lumen of the orifice of the parotid gland of an infant aged 4 months. The gland had undergone pathological change, and had therefore been extirpated. The organisms, which were roundish and three to four times the size of the normal epithelial cells of the gland, were without a membrane and possessed a nucleus in which the chromatic substance appeared to be contained in a karyosome. Bass and John’s[30] (Feb. 1915) and Smith, Middleton and Barrett (1914) state that _E. buccalis_ is the cause of pyorrhœa alveolaris. [30] _Journ. Amer. Med. Assoc._, lxiv, p. 553. _Entamœba undulans_, Aldo Castellani, 1905. Under this name a protozoön is described which A. Castellani found in addition to _Entamœba histolytica_ and _Trichomonas intestinalis_ in the fæces of an European planter living in Ceylon, who had suffered from amœbic enteritis and liver abscess. The shape of the body was roundish or oval, 25 µ to 30 µ in the greatest diameter. It was without a flagellum, but with an undulating membrane, and capable of protruding a long pseudopodium from different parts of its body at short intervals. The nucleus could not always be recognized in life; it was, however, always demonstrable by staining. One or two contractile vacuoles were present. The protoplasm was finely granular, showing no differentiation into ecto- and endo-plasm. According to Braun, in spite of the author declaring himself expressly against the flagellate nature of the parasite, such a nature may be assumed to be tolerably certain in view of the description and illustration. It is now considered that _Entamœba undulans_ is a portion of a flagellate, namely, _Trichomonas_. *Entamœba kartulisi*, Doflein, 1901.