The nomenclature of the parasitic flagellates of invertebrates is in such a state of chaos at the present time, that I have collected the history of the three more important genera Leptomonas, Herpetomonas, and Crithidia, in the hope that it will end the controversies which surround the application of any one of these names.

The following descriptions relate to a new species of Amblyomma in all its stages, to two species of Haemaphysalis of which diagnoses of the males and females are given, and to the hitherto unknown larva of Ixodes putus:

Under the term “Spirochaetosis” are included those diseases of man and animals due to the spiral microorganisms known as spirochaetes. I shall confine myself to those which produce blood infection—the relapsing fevers—in which a remarkable periodic increase and decrease in the number of the spirochaetes is observable corresponding to alternating rises and falls of the host's body-temperature. Authority is divided as to whether the spirochaetes are Protozoa or Bacteria, and the matter is a fruitful theme of discussion upon which I shall not enter here. Judged, however, from their pathological effects and their prompt reactions to immune sera and certain drugs, they show a pronounced affinity to Protozoa and exhibit phenomena not hitherto observed in Bacteria.

The trematode described in this paper was found by Dr Alexander Brown, British Central Africa, in the stomach of a Rhodesian hartebeest (Bubalis sp.). About 120 specimens were collected and placed at my disposal for investigation by Dr John Rennie, Lecturer on Parasitology in this University, to whom I am much indebted for the use of the interesting material. The specimens proved to belong to a new species to which the name Gastrothylax bubalis has been given. Although a fuller knowledge of recorded species rather than the recovery of new trematodes is to be desired, it is hoped that the description of this parasite may be interesting from the fact that the genus includes only ten other known species.

In a paper published in April, 1910, I described and figured a new intracorpuscular parasite found in smears made from the spleen and liver of a jackal (Canis adustus), the animal having been shot by Mr W. F. Cooper in British East Africa. As I stated at the time, I hesitated about referring the parasite to the genus Piroplasma, and only did so provisionally because it offered a resemblance to two parasites found in the internal organs of one of my dogs which had “recovered” from P. canis infection. I, however, added: “Should future investigation prove that the parasite of the jackal differs from the types of P. canis encountered in ‘salted dogs’ I would propose to refer it to a new genus, Rossiella (Rossia being preoccupied) in view of its specific name.”

The term trypanosomiasis is applied to-day to a group of diseases affecting vertebrates and caused by parasitic Protozoa belonging to the family Trypanosomidae. These parasites occur chiefly in the blood plasma and the typical form possesses an elongated body, an undulating membrane, a single nucleus, a blepharoplast, and a chromatic filament running along its length from near the blepharoplast, along the margin of the undulating membrane, to terminate freely at one end of the body. The latter has a somewhat spiral form, the protoplasm being alveolar and at times showing a granular structure. An axial filament has been described as occurring in some forms. One species, Trypanosoma equiperdum, occurs largely in the lymph, and another, T. gambiense, may invade the cerebrospinal fluid. They are actively motile organisms, multiplying usually by longitudinal or multiple division. Numerous species of trypanosomes have been successfully cultivated in vitro in the presence of haemoglobin, and by this means many trypanosomes have been discovered in animals in which these parasites occur in such scanty numbers that their presence cannot be detected microscopically. Thus, a large percentage of birds and cattle in different parts of the world have been found to harbour trypanosomes in their blood.

On clinical grounds alone sufficient evidence is available to postulate that European relapsing fever and Central African tick-fever are caused by different, though closely allied, organisms. However, as the spirochaetes of both diseases are morphologically identical (Schellack, 1908; Darling, 1909), I should like to record some experiments and observations I made during the winter of 1910–11 in Moscow, so as to give an exact impression of the difficulty or ease with which Spirochaeta recurrentis can be transmitted to mice when compared with S. duttoni under the same conditions. Moreover, I wish to describe some appearances in S. recurrentis, the exact counterpart of which have not so far been published in the case of any blood spirochaete.

“Piroplasmosis,” or “biliary fever” in horses, has hitherto been regarded as a disease due to a distinctive parasite, Piroplasma equi Laveran. We propose to show that there are two specifically distinct parasites concerned in the production of biliary fever, and that consequently two distinct diseases have hitherto been confused under this name and under the name of piroplasmosis.

Im Jahre 1908 haben wir auf dem IX. Internationalen Tierärztlichen Kongresse im Haag einen Bericht über die Piroplasmose der Pferde und Esel in Transkaukasien erstattet und etwas später eine kurze Bemerkung darüber in russischer Sprache publiziert. Nachher haben wir aber noch einige Fälle von Piroplasmose bei den Pferden beobachtet, wobei wir die Ansicht Nuttall's bestätigen konnten über die Existenz zweier selbstständiger Arten der Pferdepiroplasmose, welche durch zwei besondere Arten von Blutparasiten der Gattung Nuttallia und Piroplasma verursacht werden.