The acephaline gregarine, Gonospora varia Léger, from the coelomic cavity of the Polychaete worm Audouinia (Cirratulus) tentaculatus (Montagu) exhibits an interesting phenomenon, in which the life-history of the parasite is closely bound up with the sexual cycle of the host. It is characteristic of the acephaline gregarines that they are, for the most part, inhabitants of the coelom, and, as a consequence, frequently live in very close association with, if not actually parasitic on, the reproductive cells themselves. The familiar Monocystis from the seminal vesicles of the earthworm is an example which is at once called to mind. So, in the case of gregarines such as Gonospora, it is a common feature for them to spend the greater part of their existence free in the body cavity among the host's genital products. Naturally, they are reliant on the host's method of expulsion of the ova or spermatozoa for the dispersal of their spores. We therefore find that the periodic annual spawning of the worm is accompanied by a corresponding periodicity in the life-history of the parasites, which probably results in the reproductive bodies of both parasites and host being expelled together. In this point there seems to be a somewhat greater degree of specialisation than in Monocystis, where it is generally accepted that the spores are shed only on the death of the earthworm, either naturally or as the prey of some bird.

1. Egg masses of Limnaea truncatula collected in March 1925 were isolated and hatched in the Laboratory. The average number of ova per mass (for 20) proved to be 9·75.

2. The hatching period lasted 12 to 26 days, with an average of 20–21 days (for the Spring generation).

3. On hatching, young snails were isolated, reared, and again oviposited during the first week of July. Ova from these snails again hatched during the first week of August.

4. It is thus shown that L. truncatula is self fertile; that oviposition can commence at a shell altitude of 4 to 4·5 mm.

5. Further data on growth-rates were obtained, showing that two (and probably three) generations occur between March and October.

Since the publication of the original paper by Audouin and Milne-Edwards (1826, Ann. Sci. Nat. vol. IX), no investigator appears to have thoroughly examined Nicothoe astaci. It therefore seemed to me desirable that this Copepod should be reinvestigated by modern methods in respect to the morphology of its appendages.

The material for this paper was obtained partly at Allahabad and partly at Nagpur from Rana tigrina. In those dissected at Nagpur Centrovitus pentadelphi n.g., n.sp., was found in the duodenum and in the intestine and but once in the oesophagus. This species was also found in the duodenum and intestines of the frogs at Allahabad, but there in addition was obtained once from the stomach and once from the rectum. Ganeo glottoides (Klein, 1905) was found but twice in the intestines of frogs at Allahabad.

In a collection of the early stages of Simuliidae, made by Mr F. W. Edwards, in the summer of 1923, from the rapids above Tännforsen waterfalls, Sweden, there are representatives of 11 species of Simulium: larvae and pupae of S. venustum Say and S. tredecimatum Edw., larvae of S. morsitans Edw. and S. reptans var. galeratum Edw., pupae of S. tuberosum Lundstr., larvae and pupae of S. pusillum and pupae of S. pallipes Fries and S. lyra Lundstr., besides pupae of three other indeterminable species. In a previous paper I have already described, in detail, the early stages of the first five species, and in the present paper I deal for the first time with the remaining six species and the early stages of S.ferruginum Wahlgr. The pupae of S. pusillum Fries, S. pallipes and S. lyra were identified by Mr Edwards, by dissecting out the male genitalia, but those of the remaining three species, herein described as species I–III, are indeterminable owing to their immaturity. It seems inadvisable to give the pupae new specific names as further investigation may prove that they belong to well-known Continental species.

Tremiorchis ranarum nov.gen., nov.sp., was first found in the small intestine and duodenum of thirty-six out of one hundred and two specimens of Rana tigrina examined for the purpose. Subsequently many more frogs have been examined and we have obtained these parasites in one out of every three frogs. Rana tigrina being the commonest species of frog available in Northern India is used as the type for dissection in every laboratory and it appears, therefore, strange that this common Trematode parasite should have remained unknown till now. The number of parasites in a host is very variable. Three hosts were found infected with one parasite each, one had 4, one had 5, one 16, one 18, one 196 and one as many as 204.

A Ciliate, which seems to be new, has recently been discovered in the caecum of cattle in Cambridge. Out of 8 cattle examined 5 were found to be heavily infected, while in 10 sheep and 4 goats there was no infection. I have given the name Buxtonella to the new genus that has had to be established, as it was through the kindness of Prof. Buxton, Director of this Institute, that I obtained the material in which it was first found. The specific name refers to the grooved ridge or furrow which forms the most conspicuous feature of this species.

Sieboldiellina planariarum is a large astomatous ciliate parasitic in the gut of the freshwater Triclad Planaria torva. The writer's attention was first called to it at Cambridge in 1923 whilst demonstrating the structure of Planarians collected from ditches in the neighbourhood.

The specimens herein described were obtained from the gills of Somniosus microcephalus Block, at Excursion Inlet, Alaska, in 1909. This shark is also the host of Onchocotyle borealis, the species most closely resembling the new species, and is known in European waters as the Greenland Shark. To quote Goode: “This species, also called by our fishermen the ‘Gurry’ or ‘Ground’ Shark, is a native of the Arctic Seas, but on our coast ranges south to Cape Cod, and in the Eastern Atlantic at least to England, while in the Pacific it has been observed from Puget Sound northward.”

Parasitology has now become a vast subject, and it is impossible for any parasitologist to have a complete knowledge of the classification of all the groups of parasites with which he may be expected, from time to time, to deal. Almost all helminthologists, for example, are obliged to confine their special studies to one of the main groups—one dealing chiefly with Nematodes, another with Trematodes, another with Cestodes, and so on. Even within these large groups many findit impossible to keep in touch with the literature concerning more than one or two special families. But whether the field they attempt to cover be large or small, it is probable that most parasitologists find the name of the host a very valuable clue to the identity of the parasite which they are endeavouring to determine. For some groups more or less comprehensive host-lists have been published from time to time, and authors frequently include such lists even in short memoirs, presumably for the assistance of their fellow-workers. In all probability many workers find it useful to attempt to compile for their own use some kind of host-list.

It is now recognized, by all competent observers, that emetine is a specific therapeutic agent for the treatment of amoebic dysentery; but although it is known that a thorough course of emetine, in some form, will eradicate an infection with Entamoeba histolytica from most human beings, there is still complete ignorance as to how the cure is effected. The obvious hypothesis, that emetine is a specific poison for E. histolytica, has not hitherto been supported by adequate experimental evidence. It is true that observers have described experiments in which the alkaloid, in high dilution, has apparently killed various amoebae in vitro; but these experiments either ignored the peculiarly specific action of emetine in vivo on E. histolytica, or were carried out without adequate controls.

The animal under consideration, or one very like it, has been observed by most collectors of parasitic Copepoda since the publication by Grant appeared in 1827. All authors subsequent to Grant have placed it in the genus Lernaeopoda. Whilst there is a singular unanimity that the area of fixation is the eye, there is a considerable divergence with regard to the host: thus, while Grant originally found it upon the Greenland shark, Scott (1912) records the principal host as Lamna cornubica (which he also calls the Greenland shark), and quotes Norman as having obtained a specimen from Mustelus vulgaris at Polperro. Wilson (1915), an accurate observer, has no record of the host for most of the specimens he examined but stated that one came from a shark. It does not however follow that all these animals are of the same species. The following description is based on two specimens taken from the Arctic shark Squalus borealis = Somniosus microcephalus (Syn. Laemargus and Scymnus) off Greenland on 11. viii. 1923, by W. S. Bristowe.

The following paper lists the species of cestodes, not hitherto described by the author, obtained from Burmese animals during the years 1923–5. Many of the specimens were collected by Miss I. K. Reynolds while working in the Zoological Department of University College: the writer wishes to acknowledge his indebtedness to her for the use of data, material and slides. He also wishes to express his thanks to the Trustees of the Victoria Memorial Park for permission to collect helminths from animals dying in the gardens.

It has been shown by references to the writings of other workers, and some personal observations in the early part of this paper, that destruction of certain species of bacteria takes place in the alimentary canal of flies—especially in the early developmental stages of the insect—and ticks. In addition, emphasis has been laid on the remarkable sterility of the gut-contents and faeces of some parasitic and semi-parasitic blood-feeders.

That these conditions result from the operation of several factors is possible, and the bactericidal principle described in this paper may reasonably be accepted as one of these factors.

The investigation has been limited to the adult stage of the insects Stomoxys calcitrans, Musca domestica, Anopheles bifurcatus, Aëdes cinereus, Cimex lectularius and Rhodnius prolixus, and the arachnids Argas persicus and Ornithodorus moubata. In all of these a bactericidal principle has been demonstrated in the gut-contents, and, in the case of the insects, also in the faeces.

The bacteria most affected were the common sporing aerobes and the staphylococci, but B. anthracis was destroyed by gut-contents of Stomoxys, and M. catarrhalis and S. haemolyticus by those of Argas.

It may be inferred, from the results of the bactericidal and absorption tests, that the active principle in any one species of arthropod is single, but that different groups of bacteria exhibit differences in susceptibility to its action; some, such as the subtilis group, being very susceptible, are destroyed by concentrations too weak to affect other species, while others, as the staphylococci, require relatively high concentrations for their destruction, and many bacteria appear to be wholly resistant.

The bactericidal principle occurring in different arthropod species showed some differences in the groups of bacteria susceptible to its action, and in the degree of susceptibility of particular groups. Thus, the widest range of action was shown by gut-contents of Argas and Stomoxys, and the least by those of the bugs. The sporing bacilli seemed to be affected more by material from Stomoxys than by that from Argas, but, on the other hand, the staphylococci were apparently more susceptible to the action of Argas material than to that of Stomoxys. The gut-contents of the ticks had a feebly destructive action on B. pestis, while those of some insects actually enhanced its growth. This last observation is of some interest in connection with the case of the plague flea.

With regard to the properties of the active principle, bactericidal action is greater and more rapid at 37° C. than at room temperature. This action is not accompanied by any visible bacteriolysis. The bactericidal principle retains its activity unimpaired for at least six months when kept in the dry state. It is very thermostable, resisting temperatures as high as 120° C. It is not destroyed by tryptic digestion. It is precipitated from solution with proteins by alcohol or acetone, but is not itself affected by these reagents. It is not soluble in the common fat-solvents, ether, chloroform, alcohol or acetone. By allowing it to act upon repeated small doses of bacteria, it rapidly becomes exhausted, and it can be inactivated, possibly through adsorption, by large doses of killed bacteria; even those species which are not destroyed by it. It may also be adsorbed in small amount by bibulous paper.

It exhibits none of the properties of the bacteriophage, and it differs from lysozyme.

In the bactericidal action it is clear that no vital process is involved, in fact it very closely resembles the action of an antiseptic.

Regarding the source of the active principle, there is no doubt that it is formed in the stomach, but whether as a secretion of the gastric cells or as a result of the processes of digestion is not clear. (Nuttall (1908) showed that the destruction of Spirochaeta duttoni in the gut of the bed bug was definitely related to digestion.) An examination of material collected from ticks, kept at 25° C. at various stages of digestion seemed to point to an increase in bactericidal activity during the first two weeks after feeding, and a decline after the sixth or eighth week, but the activity of material from individual ticks, taken at similar intervals after feeding, often varied greatly. Control tests with the blood of the hosts, on which the arthropods were fed, showed that this was not the source of the active principle.

In a recent number of Parasitology Dobell (1926) has expressed disagreement with certain views put forward by me (1923) in a paper dealing with the coccidia of cats, dogs and man. His criticisms deal particularly with the name Isospora belli1 given by me to the coccidium discovered in man during the war, but my observations on the coccidia of cats and dogs also come under review. As regards the coccidia of these animals Dobell's criticisms would undoubtedly have been considerably modified if he had referred to a note written by myself and Sheather (1925). He has apparently overlooked this note entirely, an omission which is all the more unfortunate in that it has a very direct bearing on many of the statements made in his article.