The following is a list of parasitic Copepoda collected by L. Harrison Matthews during a fortnight's visit to Iceland in the first half of July 1922, some thousands of fish being examined at the numbered stations (St.), viz.: (1) Veetmannaeyjav (Westmanna Isles) E. 10 m.; (2) Storknaes; (3) Portland (Iceland).

The following paper is part of the result of work done in the University Museum of Zoology, Cambridge, between Nov. 1922 and June 1923. The present writer has for some years been receiving specimens of Nycteribiidae for determination, and with them there had accumulated at Cambridge a small collection of another family of bat-parasites, the Streblidae. At the writer's suggestion, Mrs Kessel undertook a systematic examination of this collection, and with it of material kindly lent by the British Museum through Major Austen and Mr F. W. Edwards, by Professor Poulton from the Hope Museum, Oxford, by Dr G. A. K. Marshall from the Imperial Bureau of Entomology, and by Mr S. Hirst. To all these gentlemen thanks are tendered, also to the authorities of the British Museum for the gift of certain named duplicates, and to Mr Oldfield Thomas for checking the names of the mammalian hosts. Thanks are also due to Mr Gillings for the care exercised by him over the drawings, and to the editors of Parasitology for accepting this paper for publication.

The four distinguished German men of science to whom the following biographical notes relate: Robert Koch (1843–1910), Paul Ehrlich (1854–1915), Emil von Behring (1854–1917), and Friedrich Loeffler (1852–1915), form a group of singular interest because of the relations that existed between them and the various problems to the solution of which they devoted their remarkable talents and energies. Each of them has left an indelible mark upon the annals of research and discovery in relation to infective diseases of man and animals, their etiology, prevention and cure. If it were at all possible to reckon up the sum of human and animal lives that they have saved from premature extinction through their collective efforts, direct and indirect, the total would attain gigantic proportions. Mankind should ever keep these men in grateful memory.

It is perhaps unnecessary to introduce this series of papers with the remark that the chief interest in the study of the Mallophaga centres about the problems associated with their distribution and that these problems are in some measure at least coincident with the problem of the genetic relationship of their hosts. All this has been said very clearly, many times and by various writers. Yet I repeat it again, for it is this interest which is responsible for the papers to follow and it is as a contribution toward the study of these problems that they are intended, notwithstanding the circuitous route that may be followed in arriving at this goal.

Paedogenesis, or the multiplication of an animal in its immature stages of life, is a very rare phenomenon and is known to occur only in a few species of holometabolic insects.

When, in 1917–18, I made a microscopic examination of freshwater snails at Potchefstroom, Transvaal, I found 10 per cent, of the examples of Isidora schackoi Jickeli infested with eye-spotted cercariae which Dr E. C. Faust recognised as amphistomes. Some shells which I collected from the same pools and considered to be immature examples of Isidora schackoi have been identified as Sericima. It is possible that the two species are identical. I found Isidora forskali at Cato Manor, outside Durban, infested with amphistomes, and confirmed this observation by isolating similar cercariae from the same freshwater snail on the Umgeni flats. I have obtained examples of Isidora forskali from Amanzimtoti, Isipingo, Clairwood, Umhl-a-tazana, Cato Manor, Inchanga station, Umgeni, Tongaat, Nonoti, Umzindusi, at Pietermarizburg, Lourenço Marques and Beira. These places constitute several new localities for the species and no Isidorae had previously been recorded from Beira. This mollusc is common in small shallow spruits and is often attached to small plants or water-lily leaves. It is seldom more than 10 mm. in length.

Dr Woodland kindly submitted to me the majority of the worms recovered by him on dissecting the mice used in his very interesting experiment (see his paper that follows), with a request for my opinion as to the identity of the species. The material, which was handed to me preserved in formalin, consisted only in part of complete specimens, a number of the worms having been broken up during collection. I stained most of the whole specimens with dilute haematoxylin and mounted them in Canada balsam. Upon microscopic examination it became evident that the specimens were of various ages and degrees of maturity, and one specimen was of exceptionally large size. This individual, in a fairly contracted condition, measures (after mounting and without stretching) 36 mm. in length, and has about 650 recognisable segments. Mature segments (i.e. segments with testes and ovary both fully developed) begin to appear-at about the 320th segment from the scolex, and gravid segments at about the 490th. There are thus about 160 gravid segments. It will be evident from these details that this specimen agrees with my description of “Hymenolepis longior.” Two of the young forms among Dr Woodland's material also seemed to agree with “H. longior” rather than with what I had regarded as H. nana.

Cis Bidentatus, which acts as host to this gregarine, is a small fungus-eating beetle. Almost all the beetles examined proved to be infected, but the parasites were never very numerous in each host. As a rule the infected beetles contained from four to eight of the sporont associations, and sometimes a few of the cephalont stages or cysts. The adult gregarines may be seen by transparency through the wall of the mesenteron: they lie either straight or else bent in the form of a U, but always with their long axis parallel to the sides of the gut. They are restricted to the posterior region of the midgut, and are never distributed along its whole length.

The pigeons of India are notoriously heavily infected with tapeworms and a cursory examination showed those of Rangoon to be no exception. A systematic investigation, the results of which are given in the accompanying table, was made of 20 pigeons taken from various parts of the town. Those from some localities were comparatively free from infection, others heavily parasitised. On the whole, those kept in cages and fed on corn had the greatest percentage of worms. The effect upon the health was very pronounced. Extreme emaciation and weakness were the usual accompaniment to a heavy infection. The worms were mostly situated in the duodenum, Hymenolepis nearer the stomach, Cotugnia and Raillietina further away, but this arrangement was liable to be altered. In one case, a bird on the point of death, the worms had moved nearly to the anus, some remaining free, others attached, indicating the probability under normal conditions of the cestode moving from place to place.

Although Parasitology, broadly interpreted, includes the study of parasitic bacteria within its sphere, bacteriology is excluded from consideration here because it is assumed that a knowledge thereof is sufficiently recognised as essential by those who deal with medical education. At any rate bacteriology is more or less adequately taught to medical students and candidates for the Diploma in Public Health, although it receives insufficient consideration in courses leading to the Diploma in Tropical Medicine and Hygiene. On the other hand, parasitology is taught to candidates for the latter diploma to the limited extent that is allowed in the too short courses of instruction that are at present given for the diploma. Medical students in general learn next to nothing of parasitology beyond what they pick up in the course of their preliminary zoological training. I base these statements on personal experience, extending over many years, as teacher and examiner. Similar conclusions to these have been reached by others who are able to form an objective opinion.

Although the common Filariid parasite of the Camel was identified as a distinct species more than forty years ago (Lewis, 1882), the recent memoir on Indian Nematodes by Baylis and Daubney (1923) contains the first intelligible account of the structure of the adult worm. Their description of the species, which they refer to the genus Acanthocheilonema, is based partly on some rather fragmentary material received from the Zoological Survey of India, and partly on notes and drawings supplied by Major F. H. Stewart, I.M.S.

1. Of 20 mice (previously ascertained to be free from Hymenolepis infection for a period of at least 42 days), artificially infected with Hymenolepis eggs, only one failed to show definite evidence of Hymenolepis infection when examined from three to 24 days after. Of nine control mice none showed infection during a period of at least 53 days and were found to be uninfected when killed. Of five further control mice which were subsequently artificially infected, four were found to be free from infection when killed.

These results prove conclusively that direct infection, i.e. the infection of one mouse by ingestion of the eggs laid by the Hymenolepis of another mouse, can take place without the intervention of any intermediate host. The one-host account of the life-cycle of Hymenolepis fraterna promulgated by Grassi and Rovelli and Joyeux is thus the correct one, though this does not exclude the possibility of the Hymenolepis egg occasionally developing into a cysticercoid inside the body-cavity of a flea and undergoing the rest of its development when the flea is eaten by a mouse. I have not ascertained whether or not a mouse can re-infect itself by swallowing Hymenolepis eggs contained in its own faeces.

2. Hymenolepis fraterna individuals of the same age (i.e. developed from eggs ingested at the same time) often but not always develop at very different rates in different mice and in the same mouse. Grassi and Rovelli's statement that Hymenolepis fraterna takes from 15 to 30 days to become mature is approximately correct.

Hymenolepis fraterna can become mature, i.e. possess ripe eggs in the hind proglottides, when only 6 mm. or 7 mm. long. In cases of heavy infection (e.g. 100–200 individuals in a single mouse) the worms probably always remain of small size (ca. 10 mm.) as compared with the worms in light infections where they attain a length of 20–25 mm.

Eggs can be shed as early as the fifteenth and probably on the fourteenth day of development.

3. It is probable that mature H. fraterna often sheds all its eggs within a period of a week and often less, the eggless and degenerate worm then being voided in the faeces.

4. In artificial infection of mice definite results can only be obtained with heavily-infected faecal material. Occasionally mice appear to be immune, but, judging from my experiments, such immunity is rare in mice of medium size. I cannot confirm Joyeux's statement that very young mice are most susceptible to infection. Out of some 200 mice examined I found that the smallest and largest mice were least liable to be infected, medium-sized mice supplying all my infected faeces. The largest mouse (over 35 gm.) in my experimental series, on the other hand, became infected with a weak concentration of eggs.

Eine besonders geeignete Gruppe zur Untersuchung verwandtschaftlicher Beziehungen und zur Feststellung der Wege, die bei der Art- und Gattungsbildung eingeschlagen werden, scheinen gerade die Zecken zu sein, da sie alle unter verhältnismässig gleichartigen Bedingungen leben und in nur wenige Gattungen zerfallen, die aber zahbreiche Arten aufweisen.

1. Out of 57 mice (previously ascertained to have been free from “H. fraterna”) 30 were fed on fresh eggs of Hymenolepis nana, the other 27 serving as controls. Out of the 30 egg-fed mice, only 7 were found to be infected (23·3 per cent.) when examined from thirteen to twenty-six days afterwards. None of the 27 control mice showed infection.

2. This low percentage of infection (when compared with the 90 per cent, infection obtained in my previous work when I fed 20 mice on “H. fraterna” eggs) is probably due to one or more of three factors: (a) change of host (Grassi records that he found it very difficult to infect wild rats with “H. fraterna” eggs obtained from tame rats and in this case the animals were of the same or closely allied species); (b) the full-grown adult condition of the mice; (c) the perfect health of the mice, due to having been supplied with vegetable food (Vitamin B) every day, this condition rendering the mice refractory to infection. In my previous work the mice were in poor condition owing to deficiency of Vitamin B.

3. The proof that rats and mice can be infected with H. nana eggs from Man, the identity of structure of the two parasites and their eggs and their uniform geographical distribution render it practically certain that H. nana and “H. fraterna” are one and the same species. The fact that up to the present there is practically no evidence that Man can be infected with eggs derived from rats or mice does not militate against this conclusion.

4. Mature specimens of H. nana found in tame mice vary enormously in size (as already indicated by Joyeux)—between 7 mm and 80 mm. (measured in balsam) in length. “H. longior” (Baylis, 1922) does not exist as a distinct species.

5. I failed to infect two Cercopithecus monkeys fed with a plentiful supply of fresh H. nana eggs (from Man).

6. Experiments are described which confirm Joyeux's statement that H. diminuta (of the mouse), unlike H. nana, does not possess a direct one-host life-cycle.

The anatomy of the bed-bug has been described many times by other writers. There is therefore no intention in the present paper of dealing with more than those parts of the anatomy which have been described incorrectly or insufficiently or have been omitted from the descriptions. Such are the mouth-parts, salivary pump, salivary glands and nephrocytes and with these subjects accordingly this paper deals exclusively.

The monogenetic trematodes have long been known as parasites of the lower aquatic vertebrates and many forms have been described from fishes, amphibians, and reptiles. They are largely ectoparasitic, although a few members of the group infest the oronasal cavities and urinary bladder of frogs and turtles. Up to the present there appears to be no record of their occurrence on either birds or mammals and consequently the unusual case here reported seems worthy of note. The material consists of five polystomes which bore the label, “from the eye of hippopotamus.” Presumably they were collected by the late Professor A. Looss from a Nile hippopotamus in the Giza Zoological Gardens of Cairo, Egypt, but unfortunately no particulars are available. The specimens were given to me for identification by Dr Edward Hindle, recently Professor of Biology, School of Medicine, Cairo, to whom I wish here to express my thanks. Grateful acknowledgments are due also to Professor George H. F. Nuttall, Director of the Molteno Institute for Research in Parasitology, where the study was made.

On June 10th, 1923, a practising veterinary surgeon brought into the Pathological Laboratory at the University scrapings that he had obtained from a herd of cattle which were suspected of being mangy. The sample was examined for mites without success. The veterinary surgeon said that the lesions were not typical of mange, but if it was not mange, it was some form of dermatitis which was unknown to him.

In Parasitology, vol. xv, p. 340 (20. ix. 1923), I described a genus of nematodes from the rabbit for which I proposed the name Obeliscus. Dr Paul Bartsch, of the Smithsonian Institution, has called my attention to the fact that this name is preoccupied, having previously been used for genera of Mollusca by Humphreys in 1797, by Agassiz in 1837, and by Beck in 1837. I therefore propose the new name Obeliscoides, type cuniculi, to replace Obeliscus Graybill, 1923.