When examining the contents of the alimentary canal of caddis-fly larvae, I found that in addition to certain well-known gregarines, they generally harbour several other interesting protist parasites which have not hitherto been described. Chief among these are: (a) a tricho-mastix, (b) a spirochaete, and (c) a flagellate which appears to be related to Macrostoma caulleryi, Alexieff. The present paper deals with the trichomastix and the spirochaete: I hope to describe the other flagellate fully in a future communication.

1. Musca domestica and other non-biting flies frequenting similar feeding-grounds, are probably all liable to infection with a common flagellate. The great variability of this form is shown on comparing the flagellates in the larvae with those in the mature flies of Homalomyia, sp. and of Scatophaga lutama.

2. Infection is casual–i.e. by the mouth. In the case of the dung-flies examined, the larvae ingest faecal matter infected with herpetomonad cysts: the cysts develop into flagellates in the mid-gut, where they multiply with great rapidity: towards the close of larval life, when the larva stops feeding, they round up in the hind-gut, and are for the most part passed out as cysts. A few survive the pupal stage in a half-encysted condition, but it is probable that the infection of the adult fly is usually freshly acquired. The cycle in the fly is similar to that in the larva, and is in agreement with Patton's account of Herpetomonas muscae-domesticae. The parasite was never found in the ovaries or ova. Patton's suggestion that the degree of infection depends directly on the number of cysts ingested, is borne out by the much higher rate of infection in the larvae than in the flies: this is not surprising when we remember the complete restriction of the feeding larva to the infected area.

3. It is important to use some reliable cytological stain such as iron-haematoxylin as a control to Romanowsky stains where possible, seeing that very different results are sometimes given by the two methods.

4. The apparent double flagellum is produced in the course of longitudinal division. The new flagellum grows up alongside the old, and is not merely split off from it: this is best seen in the flagellate from the larva, where the body of the organism usually divides at an earlier period than in the fly. Study of the living flagellate is necessary to a clear understanding of the process of division.

5. I have seen no conjugation in the living herpetomonads. Occasionally flagellates were met with in Giemsa preparations devoid of a tropho-nucleus. Such individuals might be regarded as male gametes; it is more likely that they are simply degenerate forms. Sufficient consideration is not given to the possibility of degeneration in richly-nourished, rapidly multiplying protozoa, such as the trypanosomes and their allies.

6. In encystment the flagellum is not cast off bodily, but is drawn down into the cell by the kineto-nucleus, which moves to a position either alongside of, or posterior to the tropho-nucleus. In this way apparent Crithidia or even trypanosome forms are produced, but there is no hint of an undulating membrane. Small blunt “trypanosomes” were also produced occasionally by adhesion of the flagellum to the body-wall in the “stickiness” resulting from confinement under a cover-glass: the efforts of the flagellum to free itself raised up an undulating membrane, and produced a very deceptive appearance.

7. The early stages of encystment could be induced by keeping the flagellates under waxed-down cover-slips, where they would continue to live for 30—40 hours. Similar results were got by transferring flagellates to agar-agar, or by subjecting the larval host to starvation for a day or two.

8. From what I have seen, I do not agree with Chatton and Alilaire's suggestion to divide the genus Herpetomonas into Leptomonas and Herpetomonas proper. I do not think that these authors are justified in regarding the double flagellum and the presence of a long rhizoplast as generic characters.

Through the kindness of Mr Nelson Annandale, Director of the Indian Museum, I have recently had the opportunity of examining a small collection of Pentastomids from that Museum. The collection contains one new species of Porocephalus and affords examples of new hosts and new localities in which species already known have been found. In all there were four different species.

The organism, commonly known under the name of the Bottle-bacillus (Flaschen-bacillus; Bacille-bouteille), was first described by Malassez (1874, pp. 203 et seq.), whose observations led him to the following conclusions (p. 211): “Il existe dans la pelade un champignon parasite. Ce champignon occupe les parties les plus superficielles de la couche cornée de l'épiderme; on le trouve entre ou à la surface des cellules épithéliales de cette couche. Il ne se rencontre qu'accidentelle-ment sur les cheveux, et encore siége-t-il sur des cellules épithéliales, qui proviennent de l'épiderme cutané. Il est uniquement constitué par des spores sphériques très-petites.

In a previous paper which appeared in Parasitology, Vol. III. pp. 73–07, and the Journal of Tropical Veterinary Science, Vol. n. No. I, details were given of thirty-two cases of successful treatment of Surra in horses by means of arsenic and its derivatives.

During the rainy season of 1908–9 an outbreak of disease among cattle occurred over a somewhat widespread area of the Mombera district, causing considerable losses in herds owned by natives.

At the present time Ankylostoma infection in man and disability resulting therefrom has aroused much concern. The geographical origin and present distribution of the two species of Ankylostoma known to be parasitic to man are of considerable interest, even though it be only academic. It is, therefore, probable that the following note may be worthy of publication.

The specimen of the larva of H. canicalaris was obtained from the stool of an adult man, who gave the following history:

He had been in good health and had not been conscious of any intestinal disorder. On the morning of the 28th of May he happened to look down into the pan of the closet after passing a motion and noticed that there was considerable movement taking place in the motion, which was partially formed. This movement was due to the presence of a large number of larvae, several of which crawled up the edge of the pan. He secured one and brought it to me in a bottle, and it was then alive and moving vigorously about the bottle. It maintained its vitality so long as it was in my possession, and until it was despatched to Cambridge for identification.

The following case of Intestinal Myiasis occurred in a boy about twelve years of age, in normal health, who brought to me in September 1909 what he took to be “worms” discharged with his faeces. He said he did not feel anything abnormal but saw a mass of the creatures upon and in his freshly-voided faeces. He called his mother, and she stated to me afterwards that the “worms were in a cluster like a swarm of bees,” they were crawling about the faecal mass which was loose in character, as had been the case for several days. They varied considerably in size, as did the specimens brought to me. The mass of creatures would have filled one or two tablespoons.

I Have been much interested in Professor Nuttall's paper in the April number of Parasitology (this volume, p. 113) and especially in his description of a parasite found by him in blood smears from a buffalo sent to England from British East Africa. He has named this organism Spirochaeta bovis caffris though he is evidently somewhat doubtful as to its nature. I write to say that early in 1909 I received from Captain Hadow one blood smear from a Jackson Hartebeeste which he had shot in the Bahr-El-Ghazal and on the body of which he found G. morsitans in the act of feeding. In this smear I found organisms which answered very closely to those described and figured by Professor Nuttall. They were somewhat smaller, having an average length of 16·5 μ and a breadth of 0·7 μ but presented the same appearance, stained in the same way and in some instances showed the achromatic transverse bands which he mentions. From its shape I mentally termed one variety the buffalo-horn type and I made drawings of the different forms encountered. On April 18th 1909 I sent the slide to Dr Wenyon at the London School of Tropical Medicine with a note directing his attention to these curious parasites and stating that, to me, they looked more like spirochaetes than anything else but that I was unable to classify them. Unfortunately, though my letter was safely delivered, the box containing the slide was never seen again. Dr Wenyon, however, wrote and told me that he had come across similar forms in the blood of big game which had been shot, and recorded his opinion that the forms in question were not blood parasites at all but were derived from the intestine and had been carried into the exit wound by the bullet or by discharges finding their way along the bullet track. One recognised the possibility of such an occurrence and the fallacies to which it might give rise and, on meeting Captain Hadow, I asked him if he remembered where the animal had been shot. To the best of his recollection the bullet had passed through the neck severing the gullet and it is quite possible that in the last throes stomach contents might have regurgitated through the wound of exit. The presence of very thin thread-like spirochaete forms in the film and of some bodies which suggested yeasts made me refrain from publishing any account of the case until I had more evidence regarding Dr Wenyon's hypothesis.

Dr Balfour's note raises the question whether Spirochaeta bovis caffris is a blood parasite or an organism derived from the alimentary canal owing to the entry of intestinal contents into the blood or blood stream consequent upon the effects of gunshot wounds. I must confess that this source of error did not occur to me in this case.

The material on which the following notes are founded was collected during a short residence at the Marine Biological Laboratory, Millport, in August, 1908. A comprehensive survey of the marine fauna was impossible in so limited a time, but a fair idea of the parasites of some of the common fishes was obtained. I have to thank the Government Grant Committee of the Royal Society for enabling me to undertake this work. It is also necessary to gratefully acknowledge the courtesy of several members of the West of Scotland Marine Biological Association and of Mr Elmhirst, the director of the Millport Laboratory.

From the results of our experiments we may conclude that the development of T. lewisi outside the invertebrate host is not confined to one species or genus, but may take place at least in the rat louse and the rat flea and also (though perhaps more incompletely) in the bed-bug. We see further that development needs not always to be combined with longevity in the invertebrate host, but that sometimes life without development may be longer than with it (behaviour in the tick compared to that in the louse).

When we compare the behaviour of T. lewisi in the four invertebrate hosts studied here, we see that the most complete cycle takes place in the flea, where forms are produced which are never found in cultures. In the louse the development may be truly described as a natural culture; in the bug, the development (as far as we could judge by our incomplete experiment) does not even produce all the cultural forms (only the crithidiae) and at last in the tick the trypanosomes do not develop at all but are only preserved for some time.

We finish this paper by thanking Professor Nuttall for the liberal way in which he enabled us to carry out these experiments, and for the keen interest he always took in our work.