He thought they should not draw so hard and fast a line between forms which were herpetomonas and forms which were trypanosomes. It was very likely that herpeto- monas was the primitive form of flagellate which, in biting flies, had gained entrance to the bodies of verte- brates and had there become a trypanosonie. In the majority of the trypanosomes of vertebrates there was no herpetomonas stage known in the vertebrate host. By herpetomonas forms he meant those in which the nucleus and micro-nucleus were arranged in the opposite way to which they were iA the ordinary trypanosomes. There were stages in many forms of trypanosomes which closely resembled herpetomonas. The Trypanosoma theileria parasite of South African cattle was an example ; both forms were also to be seen in the case of a trypanosonie of a snake recently discovered by him. A German investi- gator had lately described a trypanosorae which showed both herpetomonas and trypanosome forms. The French Commission, which was investigating trypanosomiasis at the present time, had given a description of the develop- ment of trypanosomes in the proboscides of Glossina palpalis ; the trypanosomes in this case developed into typical herpetomonas forms which remained attached to the inner surface of the proboscis. This fact, and other facts similar to it, had been brought forward in support of the contention that trypanosomes might develop into herpetomonas. It was a curious thing that the influence of the blood of the vertebrate host on herpetomonas seemed to produce the trypanosome type, while the reverse was also true that when the trypanosorae left the verte- brate host it tended to revert to the herpetomonas type. The cultivation of trypanosomes in test-tubes gave rise to herpetomonas forms, and it was probable that trypano- somes in the intestines of insects gave rise to herpeto-
