GENUS: VAHLKAMPFIA 177 



of a ring of spherical chromosomes, is arranged. The nuclear membrane 

 disappears during the process, leaving a sharp, pointed spindle in the 

 cytoplasm. The spherical cysts measure from 10 to 14 microns in dia- 

 meter. They have a smooth inner wall and a much wrinkled outer one. 

 The amoeba does not multiply within the cyst, nor does its nucleus undergo 

 division. When grown on the surface of agar, it not infrequently happens 

 that amoebae with two or more nuclei encyst, in which case a correspond- 

 ing number of nuclei occur within the cyst. 



There are other amoebse of relatively small size belonging to the genus 

 Hartmannella, which differ from one another in the details of their nuclear 

 divisions. Thus H. glehce-, described by Dobell (1914 a), is very similar 

 to H. hyalina (Fig. 56). The spindle formed during nuclear division has, 

 however, rounded ends instead of pointed ones. The cyst, moreover, has 

 a smooth outer surface. This form, or one closely allied to it, often occurs 

 coprozoically in faeces, and can be cultivated on agar plates (Fig. 56). 

 At the present time it is impossible to identify many of these coprozoic 

 amoeba?, but it appears that two fairly well-defined types commonly 

 occur — the one corresponding to H. hyalina, and the other to H. glebcp. 



Genus: Vahlkampfia Chatton and Lalung-Bonnaire, 1912. 

 Vahlkampf (1905) studied the development of an amoeba, which he 

 designated Amceba Umax. The nucleus possessed a large central karyo- 

 some, and during multiplication the nucleus divided with the formation of 

 pole caps, as in the case of Dimastig amoeba gruberi (Figs. 61 and 90). A. 

 similar form was named Amoeba 'punctata by Dangeard (1910). Chatton 

 and Lalung-Bonnaire (1912) created the genus Vahlkampfia for amoebae 

 showing this type of nuclear division and possessing pores in the cyst wall. 

 Flagellate forms of the amoebae were not observed, but the conditions 

 necessary for the production of the flagellate forms were not provided 

 by them. Several other observers have described amoebae which show 

 nuclear division of the same type, and which have not been noted to give 

 rise to flagellate forms. It does not seem improbable that most, if not all, 

 of these forms would produce flagellate stages if the necessary conditions 

 existed. Dimastig amoeba gruberi remains as an amceba on agar plates, or 

 in cultures in egg-albumen water and other media, and does not become 

 a flagellate unless a sudden change occurs in the medium, as, for instance, 

 that produced by the addition of tap water. If this is done, flagellates 

 appear in three or four hours, but they revert to the amoeboid form again 

 in about a day (Fig. 120). It is probable that many of the amoebae which 

 have been placed in the genus Vahlkampfia would be capable of transforma- 

 tion into flagellate forms if they were similarly treated. It is possible, how- 

 ever, that some of them would not. Hogue (1921), for example, obtained a 

 I. 12 



