medium, a herpetomonas-form similar to that which they would no doubt assume within the gut of the necessary invertebrate host. Small circular, oval or pear-shaped forms, with two nuclear masses and no locomotor apparatus, were found both in the tissues of the vertebrate host alongside with the trypanosoma- forms, and in the stomach of the invertebrate host with the herpetomonas-forms. They represented a resting intermediary stage between the two forms. Similar bodies had been described not only in cases of kala-azar and Oriental sore, but also, by several investigators, in various animal trypanosomiases. Described first by Bradford and Plimmer in nagana, and by Castellani in human trypanosomiasis, they had been seen by himself unmistakably in the cerebrospinal fluid and tissues of sleeping-sickness patients and nagana-infected animals.
He considered the life-cycles of the kala-azar parasite, of Herpetomonas lygœi and Crithidia gerridis, as sketched out by Captain Patton, to be quite incomplete. Indeed, the forms described by the lecturer were but the very first stages which could be seen equally well in artificial cultures. Evidently, Captain Patton had missed the conjugation forms, and the resulting oökinetes, and all the subsequent stages which led to the forms destined to be inoculated into a fresh vertebrate host. The forms the lecturer termed "encysted" he could not accept as such; there was no evidence whatever of encystment in either the figures or descriptions he had published. His "postflagellate" forms were identical with those he called "preflagellate," and which no doubt represented the forms taken up directly from the vertebrate host. The fact that they might occur in the fæces was no evidence; Captain Patton had not found round and oval forms alone in the fæces, but also the long, flagellate
