The parasite forming the subject of the present paper was discovered inhabiting the alimentary tract of larvae of the common rat-flea of this country, Ceratophyllus fasciatus Bosc. (see Pl. IV).

Pasteur, in May 1884, showed that if the rabies virus of the dog was passed from rabbit to rabbit, or guinea-pig to guinea-pig, it gradually became exalted in virulence and fixed in incubation period for these rodents. This fixed virus remained exalted in virulence when inoculated subdurally into other animals. Magendie held the opinion that the rabies virus, when transmitted by bites from dog to dog, lost its virulence by about the fifth passage.

The identification of species of Rhipicephalus is likely to give more trouble than is the case with any other genus of Ixodidae, for while, on the one hand, there are few species which depart greatly from the general type, on the other hand the range of variation within the species is extremely great. In no genus is it so dangerous to describe a new species from a single individual, especially if the specimen be a female.

The two flies Fannia canicularis Linn, and F. scalaris Fab. are, on account of their habits, of considerable economic importance in their relation to man. It is therefore desirable that those engaged in public health and medical work and others should have a knowledge of the breeding and other habits of these flies, which they are certain to meet in their work under circumstances of varying importance. The inquiry of which this account is the result was undertaken several years ago at the request of Dr Monckton Copeman in connection with the Local Government Board's inquiry on the carriage of infection by flies in the reports of which a portion of this paper has been included. Owing to my removal from England to Canada in 1909 and subsequent pressure of work, its completion was delayed.

In 1892 Louis Léger described three species of gregarine from the alimentary tract of the larva of Tipula: Actinocephalus tipulae, Clepsidrina longa, and Eirmocystis ventricosa2.

During the past three years I have made various attempts to raise Dermacentor variabilis through its various stages on tame rabbits and have at last been successful. Though there are still many points connected with the life-history to clear up, it is at any rate the first step towards finding ways and means for its control.

Since 1906 trypanosomes have been found in ten species of mammals by officers of the Health of Animals Branch.

Whilst examining the contents of a number of insects from the neighbourhood of Pretoria (Transvaal), a flagellate was found occurring in the alimentary canal of a Hemipterous insect, Cletus varius Dall1. Unfortunately, no observations were made on the living parasite and the following notes on its morphology are only derived from the study of ordinary dried smears, fixed in alcohol and stained with Giemsa. In consequence of the method of preparation, the finer nuclear details have been destroyed, but nevertheless we have been able to make out the main points in the structure of this parasite, and as no further material is available we have decided to publish our results in their present form.

During August and September 1909 I had an opportunity, thanks to the Government Grant Committee of the Royal Society, of making a fairly comprehensive examination of the parasites of fishes from the English Channel at the Marine Biological Laboratory, Plymouth. During that time nearly five hundred fishes, belonging to about 80 species, were dealt with and a very extensive collection of parasites made. A considerable number of species were obtained many of which are new to British waters but the number of absolutely new species amounted to very few. Of these I am describing here four of the most noteworthy, three of which appear to be of new generic type. A complete account of the investigations will be published later.

The haemogregarine which is the subject of the present communication was obtained in material collected by me during two voyages made in a trawler in July 1910, round the Shetlands and the north coast of Scotland. It was found in large adult specimens of catfish (Anarrhichas lupus), taken by otter trawl from a depth of 50 to 80 fathoms, in the vicinity of Fair Isle and Foula, and on Whitenhead Bank about nine miles to the N.N.E. of Cape Wrath. Catfish taken near Rhona and Sulisker in the Atlantic showed no infection, but the number of fish examined was so small that one could not assume the infection to be absent in this locality.

In my “Revision of the Genus Stilesia” I had to leave several points in the anatomy of Stilesia globipunctata (Riv.) undecided, as the material I had of the worm was too macerated to allow of any definite conclusions. At the same time I pointed out, that the topography of the male canals as described by Stiles and Hassall disagreed with the conditions obtaining in Stilesia hepatica Wolffhügel, in other respects a very closely related species. The necessity for a re-examination of Stilesia globipunctata (Riv.) in order to decide whether the differences really exist, or whether they were supposed to do so, on account of the material examined by Stiles being rather macerated (loc. cit. p. 74), was all the greater as Stilesia globipunctata (Riv.) is the type species of the genus Stilesia. Through the kindness of Mr Littlewood, Chief Inspector of the Veterinary Department, I was able to obtain living examples of Stilesia globipunctata (Riv.) at the Cairo abattoir on Jan. 27, 1912. These worms have been fixed with Zeuker's solution, hardened and cut.

I propose in this paper reviewing very briefly the work which has been done on the Ceylon pearl-inducing worm, during the last ten years. This is particularly appropriate at the present time as the Pearl Banks—which have been under lease to a London Syndicate, who have spared no pains or money in the investigation—may at an early date revert back to the Government. It remains to be seen to what extent the Ceylon Government will profit by these investigations, and whether they will continue the work with the vigour which has characterised the Company's administration.

In September, 1908, an opportunity was afforded me of examining some of the larger food-fishes brought in to Aberdeen fish market. For this I have to thank the courtesy of Professor J. Arthur Thomson, who kindly provided the necessary laboratory accommodation, and was of great assistance to me in various other directions. I have also to thank the Government Grant Committee of the Royal Society for defraying the expenses of procuring specimens.

History. Trypanosomes have been cultured from the blood of cattle in many parts of the world; in Germany, Denmark, Greece, Holland, France, Russia, Japan, the Philippines, Siberia, Algeria, Tunis, the United States and Brazil. But in only a few cases have the actual parasites been found in the circulating blood. From the scanty literature at my disposal, but especially from the Sleeping Sickness Bulletin, I find that the following observers have found and described the trypanosomes in the blood.

The following generic names of animals reported as parasites of man have been submitted to the International Commission on Zoological Nomenclature, by the Helminthological Society of Washington, for inclusion, in the “Official List of Zoological Names”:

In the last issue of Parasitology a description is given by Wenyon (5) of the developmental cycle of Leucocytozoon canis in the tick Rhipicephalus sanguineus. Wenyon refers to the description of the development given by me (2), but rightly points out that one stage, that of the large compound cysts, was overlooked. The surmise, however, that these large and easily ruptured cysts were overlooked owing to their having been broken up in the preparation of films is only part of the truth. A full explanation involves facts in regard to the development of this parasite which have not been touched upon by Wenyon; it is possible, as will be seen shortly, that Wenyon's description of the cycle, like mine, involved a considerable error. In this respect, as a result of work not yet published, I am able to supplement what has been written on the subject.

1. All stages of Argas persicus are negatively phototropic. In addition, they are also susceptible to pronounced differences in the intensity of the illumination and select the darker places.

2. In the gorged state, the ticks are slightly positively geotropic. In the unfed state, this property is not developed.

3. At all stages the tick endeavours to bring as much of its surface as possible in contact with its surroundings.

4. A. persicus is attracted by heat.

5. In all stages an olfactory sense is well developed.

6. “Haller's organ” is olfactory in function and constitutes a means by which a tick is able to recognise its host. By depriving ticks of this organ it is possible by suitable means to cause them to feed on media other than blood, thus showing that a sense of taste is absent. Argas persicus, Ornithodorus moubata and Hyalomma aegyptium have all given similar results with regard to the latter point and we believe that this constitutes a method by which perhaps other blood-sucking arthropods, after being deprived of the organ or organs necessary for the recognition of their hosts, may be made to feed on any desired medium.

I have been following the valuable contributions which Hindle has recently been making to the literature of spirochaetosis and I have been specially interested in his paper on the above subject which appeared in Parasitology, vol. IV. p. 463. I wish to make a few comments upon some of his findings and conclusions.

Die unter diesem Titel in Vol. iv, No. 4 dieser Zeitschrift erschienene Arbeit V. Huffman's gibt mir Anlaß zu folgenden Bemerkungen, nicht weil ich ihre Ansichten nicht teilte, sondern weil sie geeignet ist, über meine Stellung zu der Frage der Kurloff-Körper einen unrichtigen Eindruck zu erwecken. Im ersten Absatz der Arbeit steht der Satz: “Therefore it is not with surprise that we find Ferrata, Patella, Goldhorn and Schilling and others believing these bodies to be protozoan in nature. Patella however is the only one who claims to have observed a flagellate develop from a Kurloff-body and of course this observation would put an end to all dispute if it could be verified.” Die Arbeit wendet sich indessen nur gegen die Patella'schen Anschauungen, obgleich im Literaturverzeichnis meine Arbeit über die Aehnlichkeit dieser Einschlüsse mit Chlamydozoenkörpern zitiert ist. Die gegen Patella angeführten Beweisgründe decken sich im wesentlichen mit den meinigen (abgesehen von durchaus negativen Flagellatenuntersuchungen, deren Zugehörigkeit von vornherein sehr unwahrscheinlich war), sind aber gerade im morphologischen Teile weit weniger eingehend und führen zu dem gleichen Ergebnis, daβ die Kurloff-Körper sicher keine gewöhnlichen Protozoen sind. Statt aber meine ihm bekannten Resultate zu bestätigen, erwähnt der Autor mich kurz unter den Anhängern der Protozoennatur der Kurloff-Körper. Mit der von mir betonten Aehnlichkeit mit Chlamydozoenkörpern ist keineswegs gesagt, daß sie wie diese noch ziemlich zweifelhaften Gebilde nun wirklich Erzeugnisse einer Infektion (höchstens mit ultravisiblen Erregern) sein müßten; ich habe ausdrücklich ausgesprochen, daß das, was von den Kurloff-Körpern dargestellt wird, eine Reaktionsstruktur der Zelle selbst vielleicht ihres Kerns auf eine unbekannte Ursache zu sein scheint.