Leeches are common in the fountains and pools of Palestine, particularly in the northern parts, known to us familiarly as ‘Galilee,’ and further north in the district of the Lebanon. In the later summer and autumn months they are so plentiful in places that almost every horse and mule passing through these parts has a bleeding mouth. Under such conditions it is not wonderful that human beings from time to time are attacked. The domestic supplies of water are usually protected by the water-carrier's custom of straining it through a piece of fine muslin as he or she fills the pitcher. In some parts of the land the water at the source is kept free from leeches by means of fish; at Deishun, for example, a village in ‘Upper Galilee’ inhabited by Algerian settlers, the large stone tank into which the spring runs is full of a special fish—Capoëta fratercula, a kind of carp—which is there bred for the purpose and which is treasured by the inhabitants with superstitious reverence. Many of the springs in the mountains of Galilee and in the Lebanon are widely known for the multitude of leeches which lurk in their waters, but a thirsty traveller seldom has self-control enough to restrain himself from drinking, and when he does so, particularly at dusk or in the night, he is very likely to suck one in. It is stated in Allbutt and Rolleston's System of Medicine (2nd ed. Vol. II. Part II. p. 959) that the leech “remains in the stomach for a time and then begins to wander.” I have had a long experience of leeches as human parasites but have never seen nor heard of a case like this. The leech in every case I have met has attached itself to the mouth, throat, etc. in the process of swallowing, and I am convinced that once the leech reaches the stomach it is killed. I have never heard of any after symptoms from cases where to my knowledge a leech has been completely swallowed. Many patients can describe the actual moment (during deglutition) when the leech seizes on the throat. One would suppose from the great frequency of leeches in the mouths of horses, etc., that they must sometimes find a temporary resting place there in the human subject; such cases do not however come into the hands of a medical man—the patient or his friends readily removes such an intruder. In the cases, some three dozen or so, which I have had under my own observation the leech has been attached to the epiglottis, the pharynx, the nasal cavities, or—most common of all—the larynx. The frequency of the last situation in my clinical experience is doubtless due to the inability of the fellahin to do anything themselves for the relief of such cases.

In the literature relating to the Ixodoidea there are a number of cases recorded of injurious effects following the bites of ticks. We do not refer to diseases like piroplasmosis and spirochaetosis which are known to be tick-transmitted, nor to other infective processes which may start at the seat of tick's bite. The effects we refer to follow almost immediately upon the infliction of the bite and are distinctly toxic in character. These effects appear to have been more frequently observed following upon bites inflicted by species of Argas and Ornithodoros.

I owe to Prof. G. H. F. Nuttall and Mr A. E. Shipley the opportunity of examining three specimens of a West African leech sent by Dr C. Wellman from Benguella, Angola. They were described as land leeches ‘taken four or five miles from any water’ and were preserved in alcohol. A brown, vermiform object protruded from the mouth of the largest specimen.

In the course of their investigations upon different species of Piroplasma numerous observers have kept infected blood in the ice-chest, or at room temperature, for various periods of time prior to the inoculation of animals. On the evidence afforded by microscopic examination alone some observers have concluded that the parasites are capable of considerable multiplication in defibrinated blood kept in vitro. Under these conditions many corpuscles undergo haemolysis and in consequence the parasites appear to be more numerous. We believe that this source of error explains the conclusions arrived at by Lignières and others with regard to the multiplication of P. bovis in extravascular blood (see p. 253).

some hundred and ten years ago, Dr Gotthelf Fischer, in a communication dated from Vienna, described a Nematode living in the swim-bladder of the trout. He named this worm Cystidicola farionis and his description is accompanied by some rough cuts. Bosc (1802) re-described the same Nematode under the name Fissula farionis. The same worm was again described by Rudolphi (1819) under the name Spiroptera cystidicola. Dujardin (1845) mentions it under the name Dispharagus cystidicola. Later it was removed by Schneider (1860) from the genus Spiroptera and placed in Diesing's genus Ancyracanthus. von Linstow uses this generic name “with a difference”; he spells it Ancryacanthus.

Since the discovery of the parasite Kala Azar by Lt.-Col. Leishman, R.A.M.C., a number of investigators have endeavoured to reproduce the disease in the lower animals but without success. The recent discovery of Nicolle that dogs are susceptible to an allied human parasite (Herpetomonas infantum) has added a fresh stimulus to work along these lines, and in order to see whether the dog can be infected with H. donovani I carried out some inovulation experiments, which I propose recording in this paper.

In the course of investigations conducted in Cambridge upon dogs infected with Piroplasma canis, a number of animals have been incidentally examined for intestinal parasites. In an unbroken series of 24 dogs, which died (March—September 1907) from piroplasmosis, the animals were autopsied immediately after death and the intestine examined by slitting it open along its whole length. We briefly record the results of these examinations, for the reason that similar reports do not appear to have hitherto been published in this country. All of the dogs harboured worms. Only three species of worms were encountered: Ascaris mystax, Dipylidium caninum and Taenia serrata.

The trypanosome to be described in this paper was discovered in blood films taken from the snake Erythrolamprus aesculapii (Duméril and Bibron) of tropical America. For these films I am indebted to Dr Leiper. In addition to the trypanosome there was present in the blood a haemogregarine. Though haemogregarines are very common in snakes, especially in the Tropics, where nearly every snake examined is found to harbour these parasites, the reverse is the case with trypanosomes. Several observers have recorded the presence of trypanosomes in snakes but hitherto no one has given an accurate description of one of trypanosomes of the whole group of reptiles is very limited when campared with other groups of vertebrata. On this account it seems of interest to place on record the characters of this trypanosome as it appears in the blood films mentioned above.

The nematode worms discovered by Mr Shipley in the swim-bladder of Trout belong to the species Cystidicola farionis, first described by Fischer, and considered by him to represent a new and distinct type in nematode structure for which he proposed the generic name Cystidicola. Later writers refused to accept the new genus and included it in various other groups (see Synonymy, p. 190). In accordance with an old nomenclatural practice the proposed generic name was adopted as the specific name in place of that originally given, thus Cystidicola farionis became, for Rudolphi, Spiroptera cystidicola. From a detailed examination of the various characters of C. farionis I have come to the conclusion that Fischer was correct in creating a new genus for the new forms, and I therefore propose the reinstatement of the abandoned name Cystidicola. It is also in accordance with modern nomenclatural ruling that the original specific name farionis should be adopted in place of cystidicola.

In two recent papersm Sambon and Seligmann (1907, 1908) have recorded some observations on the intracellular parasites of snakes, and have described no less than ten new species. The authors, in discussing the life histories of these parasites, have made the startling discovery that, “the life history of the haemogregarines like that of the haemoprotozoa is divided into two cycles: a schizogonic or ‘vegetative’ cycle spent in the blood of vertebrates and characterised by asexual multiplication, and a sporogonic or sexual cycle spent in the digestive organs of blood-sucking invertebrates and characterised by sexual reproduction.” The authors then go on to speak quite familiarly of young merozoites, adult schizonts, adult sporonts, and so on.

p. 48, second line from the bottom,

instead of “C. W. Andrews” read “Dr H. E. Durham.”

It is now an established fact that a number of blood-sucking arthropods and leeches are infected with flagellate organisms belonging to the genera Herpetomonas and Crithidia, and we believe that in more than one instance, these natural flagellates have been described as developmental forms of various trypanosomes which might be ingested by these sanguivora. As the whole question of the transmission of trypanosomes is intimately connected with these so-called developmental forms in invertebrate hosts, we propose reviewing in detail this important subject before recording our observations on the flagellate of Ctenopthalmus agyrtes.

The detailed structure of the spiracles in the Ixodoidea has hitherto received little or no attention at the hands of zoologists; at the same time, these organs are sufficiently extraordinary to make it a matter of surprise that, so far as our knowledge of the literature goes, not one of the numerous contributors to the subject of tick anatomy has found it worth while to undertake a complete description or to publish figures to illustrate it. Batelli (1891) gives a short account of the structure of the spiracle of a tick, presumably Ixodes ricinus, with a single figure, but with this exception we have been unable to find any further information on the subject.

In some notes on the Trematodes of Northumbria published in 1905 a few remarks were made on a larval Trematode inhabiting the liver of the common periwinkle Littorina littorea. The liver in two per cent. of the periwinkles from Budle Bay was full of rediæ containing cercariæ more or less developed, the latter agreeing in every way with an encysted Echinostomum larva which inhabits mussels, cockles and other bivalve mollusks in the same locality. So close was the resemblance that I had no hesitation in declaring them to be the same worm in different stages, but hoped for an opportunity of demonstrating this by experiment. In October 1908 through the courtesy of Professor Meek I had the opportunity of conducting some feeding experiments in the Dove Marine Laboratory, Cullercoats, which have given satisfactory results, and although it is not possible to state absolutely that the forms are identical yet the evidence is so strong that I think I am justified in regarding the young worm in the periwinkle as an earlier larval form of the encysted worm in the foot of the mussel and cockle.

Although Filaria volvulus was first described by Leuckart IA 1893, very little was known or taught of this particular nematode when, ten years later, I became a goverament official in Northern Nigeria. While other members of the Filaridae have received a good deal of attention during the present decade, Filaria volvulus seems to have been comparatively ignored. I am inclined to think, however, that this Filaria is far more common in certain parts of Africa than is generally supposed; and, by publishing the cases that have come under my notice, I hope that something may be added to our knowledge of the obscure disease it causes and that other workers will become interested in the subject. Up to the present time I have seen five cases, and ali of these carne under observation at Lokoja—a large government station in Northern Nigeria, situated at the confluence of the Niger and Benue rivers. To my knowledge this is the first time that cases of Filaria volvulus have been reported from Northern Nigeria.

1. The term Schizogregarinae Léger (1900) is the name now given to a sub-order of the Gregarinida, the remaining members of which are known as the Eugregarinae. The Schizogregarines were formerly known as Amoebosporidia Aimé Schneider (1884), a name given in misapprehension of the character of the cytoplasmic processes, fixative in function, present in the genus Ophryocystis. Two species of Ophryocystis (0. buetschlii and 0. francisci) were the only members of this sub-order known before 1900.

2. At present the sub-order Schizogregarinae contains five families: Ophryocystidae, Schizocystidae, Selenidiidae, Merogregarinidae, and Aggregatidae.

3. All these organisms show well-marked schizogonic stages in their life-history, and—with the possible exception of the Aggregatidae—follow after the Eugregarinae in their methods of sporogony.

4. In Ophryocystis and Schizocystis the schizogony is extracellular, that is, these forms are ectoschizous. The life-cycle of the former is shown in Fig. 1. In these parasites the number of the nuclei in the schizont increases simultaneously with its volume.

5. In Selenidium and Merogregarina the schizogony is intracellular, in other words these forms are endoschizous. The life-cycle of the former is illustrated in Fig. 3. In these forms the schizont is uninucleate during its growth, only becoming multinucleate at the end of the growing period.

6. Ophryocystis forms only one sporocyst, a fact which has been emphasised by Léger and Duboscq (1908), by the placing of the Ophryocystidae in a special section, the Monospora. However, this apparent peculiarity is easily explained by a process of reduction and degeneration having taken place, affecting with one exception all the gametes formed from each gametocyte. There is good morphological evidence in support of this explanation (see p. 382, and Fig. 4, D).

7. Figures of the interesting form Schizocystis gregarinoides (Léger, 1900) are not yet published, but a paper dealing with this organism is promised by Prof. Léger at an early date.

8. Aggregata differs from other Schizogregarines in that its schizogony takes place in one host (crab), while its sporogony occurs in another (Cephalopod mollusc). In this respect Aggregata resembles the Haemosporidia. The schizogonic phases in Crabs were formerly regarded as belonging to a gymnosporous Gregarine, Aggregata Frenzel, while the sporogonic phases were considered to belong to a Coccidian, Eucoccidium (Benedenia) in cuttlefishes and Octopus. Regarding this, Léger and Duboscq (1908, p. 102) write “…Aggregata, avec un changement de cycle coïncidant avec un changement d'hôte, c'est à dire qui soient à la fois digénétiques et hétéroïques.”

9. It is evident therefore that the Aggregatidae stand apart. On this account, I suggest a division of the Schizogregarinae into two sections, termed respectively, the Homoïica (to include the first four families discussed in this paper, wherein schizogony and sporogony take place in the same host) and the Heteroïca (for the Aggregatidae).

10. Among the Homoïca we have extracellular schizogony (ectoschizous forms) in the Ophryocystidae and Schizocystidae, and intracellular schizogony (endoschizous forms) in the Selenidiidae and Merogregarinidae. This difference is not merely superficial, it requires to be emphasised, and for this reason I would divide the section Homoïca into two sub-sections, termed respectively Ectoschiza and Endoschiza.

11. The classification of the Schizogregarines, which I would propose, is as follows:

12. Much further research is needed on the life-cycles of the Endoschiza, especially among the Selenidiidae, which occur so frequently in the Annelida. Sporogonic stages are at present unknown in Eleutheroschizon and Siedleckia.

13. In connection with the Aggregatidae, and to a less extent with the Selenidiidae, stress is laid upon the necessity of carefully distinguishing between “coelomic” and “gut” parasites. (See pp. 397 and 387.)

14. The Schizogregarinae form a most interesting link between the Eugregarinae and the Coccidiidea.