Before concluding the account of trypanosomes, it may be of interest to remark that several African trypanosomes develop in various species of _Glossina_, and are found in different parts of the alimentary tract and in the proboscis. Thus (_a_) _T. vivax_, _T. uniforme_ and _T. capræ_ develop in the fly’s proboscis (labial cavity and hypopharynx) only; (_b_) _T. congolense_, _T. simiæ_ and _T. pecaudi_ develop first in the gut of the fly and then pass forward to its proboscis; and (_c_) _T. gambiense_ and _T. rhodesiense_ develop first in the gut and later invade the salivary glands of the tsetse. The proboscis or the salivary glands in such cases are termed by Duke[111] the _anterior station_ of the trypanosome, wherein it completes its development. [111] _Repts. Sleeping Sickness Commission Roy. Soc._ (1913), xiii, p. 82. ADAPTATION OF TRYPANOSOMES. These flagellates may exhibit power of adaptation to changes of environment, such as those due to the administration of drugs, change of host, etc. A few examples of such mutations may be briefly considered:-- (1) _Blepharoplastless Trypanosomes_.--_T. brucei_ may become resistant to pyronin and oxazine. Accompanying this drug resistance is a change in morphology, namely, the loss of the blepharoplast (Werbitzki).[112] A race or strain of blepharoplastless trypanosomes may be thus produced which retains its characteristic feature after as many as 130 passages (Laveran).[113] Oxazine is the more powerful drug, and it acts directly on the blepharoplast. (Compare the natural blepharoplastless character of _T. equinum_.) [112] _Centralbl. f. Bakt._ (1910), Orig., liii, p. 303. [113] _Bull. Soc. Path. Exot._, iv, p. 233. (2) Reference has been made on p. 93 to the experiments of Gonder, who showed that a strain of _T. lewisi_ rendered resistant to arsenophenylglycin lost its resistance after passage through the rat louse. This is in marked contrast with the retention of drug resistance during passage by inoculation from rat to rat. (3) _T. lewisi_ from the blood of a rat when transferred to a snake seems largely to disappear, as very few flagellates are seen. When blood from the snake is inoculated into a clean rat, then trypanosomes reappear in the rat, but they are not all like those originally inoculated. It seems certain that, in such a case, changes in form and virulence of the trypanosome have occurred. Similar experiments were made with _T. brucei_ from rats to adders and other animals and back to rats. Changes in the form and virulence of _T. brucei_ occurred. These interesting experiments were performed by Wendelstadt and Fellmer.[114] [114] _Zeitschr. f. Immunitatsforschung_, iv, p. 422 (1909), and v, p. 337 (1910). Genus. *Herpetomonas*, Saville Kent, 1881.