On November 14th, 1929, the writer examined a Royal Sturgeon, Acipenser sturio L., for trematode parasites. Up to the time of writing, this is the largest Sturgeon landed at Swansea, measuring 11 ft. long, 4 ft. 9 in. girth, and weighing 565 lb.; it was captured west of Lundy in the Bristol Channel by the steam trawler Conway Castle of the Consolidated Fisheries Ltd., Swansea.

The great importance of lice as parasites and vectors of disease in man led one of us (Nuttall), soon after the outbreak of the Great War, to undertake a detailed study of these insects. It was known, prior to the war (1909–14), that lice transmit typhus and relapsing fever and during the war (1917–18) it was established that they also serve as vectors of trench fever. Beginning with February 1917, a number of papers dealing with various aspects of the louse problem were published in Parasitology (see vols. X–XIII), the study of their structure, systematics and biology being actively pursued whilst the best methods of combating them were sought for with a view to aiding the armies in the field. Of these papers, that dealing with the structure and function of the genitalia in Pediculus (II, 1917) bears directly on the subjects to which this Iconography relates.

For the material herein dealt with, I am indebted principally to Mr G. A. H. Bedford of the Division of Veterinary Services of South Africa. Other material collected by the writer from bats in the United States National Museum some years ago and a specimen received from Dr C. R. Kellogg of Foochow, China, are also recorded.

1. Eleven new species of cercariae are described from China. Of this number ten have been obtained from species of bithynoid snails and one from Planorbis möllendorfi.

2. One of these species, Cercaria beatifica, a heterophyid larva, needs to be differentiated from the cercaria of Clonorchis sinensis, which develops experimentally in the same mollusc.

3. The forms described are much more common parasites of bithynoid snails than is the larva of Clonorchis.

4. Wherever it has been possible the larval characters, particularly those of the excretory system, have been utilised to show the relationship of the cercariae to adult groups.

In the course of my previous work on the structure of the head and mouth parts of the Streblidae (1929), I encountered some difficulty in identifying the different species of the genus Raymondia. A careful examination of the specimens in the collection of the British Museum and of my own specimens showed that the descriptions and figures given by the authors who studied these insects in the dried condition are not quite adequate. In dried specimens of these minute flies it is often impossible to distinguish clearly the chaetotaxy of the head and the thorax and the characters present in the wings, which are generally interlocked. Moreover, the parts of the male genitalia lying in the abdomen are absolutely inaccessible. When examined in the cleared specimens the genitalia of the different species have been found to possess distinctive characters.

The stem infestation of Oscinella frit in England is attacked by at least two species of hymenopterous parasites of considerable importance. The species are Halticoptera fuscicornis Walk. (Chalcidoidea) and Rhoptromeris eucera Htg. (Cynipoidea). It is also parasitised to a much lesser degree by Loxotropa tritoma Thoms. (Proctotrypoidea). These three species are described and figured in detail.

The three species named above have been reared by the writer from host puparia obtained in the Harpenden district; they have also been reared in the Leeds and Oxford districts by other observers. They attack the host in the larval stage of the latter and emerge from the puparia. All three species are characteristic parasites of cyclorrhaphous Diptera.

In the Harpenden district a parasitism of 27 per cent. was observed in 1926 and of 37 per cent. in 1927, Rhoptromeris eucera being the dominant parasite.

Evidence is brought forward which appears to indicate that the parasites, collectively, become more abundant as the season advances, with the result that Oscinella frit affecting late sown oats suffers markedly heavier parasitisation than when it attacks oats drilled earlier in the season.

The time of maximum emergence of Oscinella frit in out-of-door rearing cages during the years 1926 and 1927 coincided very closely with its period of greatest abundance in the field, as recorded by Cunliffe.

In a previous paper (1924) I have discussed the reasons why a division of the order Eugregarinida into Septata (Lank.) and Haplocyta (Lank.) is preferable to Cephalina and Acephalina or Polycystidea and Monocystidea. The object of the present paper is to review the genera of Haplocyte gregarines so far described, and to attempt a classification of the same into families.

The more important points that have emerged in the course of our investigations may now be assembled.

(1) An adhesion phenomenon has been described in which, in certain circumstances, red blood corpuscles adhere to trypanosomes.

(2) We believe this red-cell adhesion to be a manifestation of the adhesion phenomenon already described by other workers both with trypanosomes and spirochaetes.

(3) The substance responsible for this phenomenon of adhesion is designated in this paper adhesin.

(4) The red-cell adhesion test has been studied in relation to several strains of polymorphic trypanosomes, all of which were either recently isolated from naturally infected man or animals, or had been recently passed cyclically through tsetse.

(5) It is shown that the adhesion phenomenon is irregular and uncertain in its appearance. A single or even a number of negative observations do not exclude trypanosomiasis. A positive reaction, on the other hand, indicates recent or actual infection with a trypanosome of the same group, but not necessarily specifically identical with that employed as antigen in the test. Thus T. gambiense adhesin bloods not uncommonly react with T. rhodesiense trypanosomes and also on occasion with the Damba strain: the converse is apparently of less common occurrence.

(6) Adhesins appear in an animal's blood in the course of its infection with trypanosomes, whether the animal be treated with trypanocidal drugs or not. When sterilising doses of such drugs are employed the adhesins gradually disappear in the course of a few months; but in untreated infections of T. gambiense they have been shown to persist in an active form for more than two years.

(7) With our material it was found impossible to distinguish between “passage” and “relapse” strains by means of the adhesion test. On the contrary it was found, at all events with T. gambiense, that the best way to call forth the reaction in the blood of animals long infected is to employ trypanosomes from a very early infection.

(8) Guinea-pigs have been found to be unsatisfactory animals in which to demonstrate adhesins; they are, however, useful as a source of sensitive trypanosomes. When only guinea-pig elements are present in a test a positive reaction is indicated by platelet not by red-cell adhesion.

(9) The presence of adhesins in the blood has no apparent relation to immunity against the homologous trypanosome.

(10) The test has been applied to over 200 human cases of trypanosomiasis in the Uganda Protectorate, and with six of these repeated observations were made. Some of these human cases reacted both to T. gambiense and T. rhodesiense, but none to T. rhodesiense alone.

(11) A partial analysis has been made of the mechanism of red-cell adhesion, which has been shown to be in some way associated with the presence of the red corpuscles of primates. This fact probably explains why other workers appear not to have noticed red-cell adhesion in the extreme form we have described in this paper.

In previous papers one of us (Keilin, 1915, 1917) has shown that among cyclorrhaphous dipterous larvae there is a remarkable correlation between the anatomical structure of the larvae and their mode of life. Although the mode of life of the larvae is in correlation with such anatomical features as thickness and hardness of the body-wall, the development of sensory organs on the head, and the structure of the alimentary canal, it is in the bucco-pharyngeal armature that the most obvious and important adaptations are to be found. The most important of these adaptations may be mentioned briefly. In certain cyclorrhaphous dipterous larvae the ventral wall of the basal sclerite of the bucco-pharyngeal armature has a number of longitudinal ridges projecting into the lumen of the pharynx. These ridges are usually Y-shaped at their free borders, and form a series of longitudinal channels in the ventral region of the pharynx. In other cyclorrhaphous dipterous larvae such ridges are absent and the ventral wall of the pharynx is smooth. This character allows the larvae to be divided into two groups—“all cyclorrhaphous dipterous larvae parasitic on the most diverse animals or on plants, as well as carnivorous larvae, and larvae which suck the blood of mammals, never have ridges in their pharynx; on the contrary, ridges are always present in saprophagous larvae” (Keilin, 1915). All the larvae which are devoid of ridges and are either parasitic, carnivorous, pass their whole life in the uterus of the female, or are phytophagous, may be united into the group of biontophagous; all larvae which have ridges are saprophagous.

Some species of very small flies belonging to the family Oscinidae have been accused of transmitting conjunctivitis and other diseases in different parts of the world.

In the first part of this paper some of the evidence apparently incriminating these flies is quoted, and in the second part an account is given of the anatomy of the mouth parts, which appear to be so modified that the flies are likely to cause minute punctures when they feed on the delicate conjunctival epithelium or on recent wounds.

1. A new variety of the trematode Harmostomum opisthotrias is reported from the North American opossum.

2. Body proportions in this genus are more constant than linear dimensions and are, therefore, considered more desirable as a basis for taxonomic distinctions.

3. The occurrence of this parasite in a host with a range as limited and a phylogenetic position as critical as that of the opossums suggests the possibility of valuable information to be obtained through host-parasite relationship studies in this group. Investigators who are working with this material should keep the problem in mind.

Bhalerao (1926) described a trematode from the common Indian frog, Ranatigrina, which he placed in a new genus Centrovitus and a new species pentadelphi. Mehra and Negi (1926) gave a fuller account of the same form, from the same host and practically the same locality, under the designation Tremiorchis ranarum n.g., n.sp.

This mite was reported by Hirst in 1923 to be causing damage to poultry in Bedfordshire. He states that, although it had previously been found in pigeons, it had not before been recorded as a pest of fowls in this country. In the United States of America it has frequently occurred, and is regarded as a dangerous parasite, but Hirst's record seems to be the only one of its occurrence as a pest in the British Isles.

Of all the commoner families of parasitic Copepoda, the Chondracanthidae has received perhaps the least systematic notice.

In a recent paper (1927) Leigh-Sharpe and I divided the Chondracanthidae into two sub-families, the Lernentominae and the Chondracanthinae, and gave a full description and commentary on the three genera which form the Lernentominae. The present paper is an attempt to summarise our knowledge of the remaining sub-family, and introduces five genera and one species new to science.

Habitat and material. By the courtesy of Prof. W. M. Tattersall of University College, Cardiff, I have been able to examine what proved to be a new species of Chondracanthus, the material consisting of a female with a male attached anterior to the abdomen as is usual. The host, Malacocephalus laevis, was taken in deep water from S.W. Ireland by the fishing fleet of M. H. Neale, Esq., the eminent Cardiff naturalist, after whom this species is named.

A detailed description of the anatomy of the proboscis of the blow-fly, C. erythrocephala, and of the functions of the structures found in it is given. Attention is particularly directed to the fact that the fly can feed in several ways. It can filter the larger particles out of its liquid food, or can scrape chosen surfaces, moistened with vomit or saliva, with its prestomal teeth and subsequently ingest the emulsion produced, or can suck up materials, such as thick sputum or faeces containing helminth ova, without the intervention of its filtering apparatus or the application of its teeth. The relation of these modes of feeding to infection is very briefly indicated.

There have been described in detail adaptations of dilution egg counting and direct centrifugal flotation for use on sheep faeces for the ova of Haemonchus contortus, together with certain data on their comparative efficiency. It is suggested that extension of the methods as given, or with appropriate modifications, would permit studies from a variety of angles on the helminthic infestations of the gastro-intestinal tract and its diverticula among domestic animals.

1. A ciliate occurring in the caecum of about 25 per cent, of the cattle that were examined at Jeanerette, Louisiana, is herein classified as Buxtonella sulcata Jameson (1926) and it is proposed that it be removed from the Class Aspirigera, Family Isotrichidae, and included in the Class Spirigera, Order Heterotrichida.

2. The ciliate is characterised by the position of the cytostome near the permanently open cytopyge and within the peristome which continues from the cytostome around the oral end of the body to the extreme aboral end which during locomotion is anterior.

3. The infections were detected in slaughtered animals by examining faecal material in Syracuse watch glasses under the binocular microscope, this method of faecal diagnosis having advantages over the smear method.

4. By the administration of Epsom salts the ciliates may be obtained from living cattle.

5. A pipette is described and figured for the isolation of Protozoa.

6. Death of Buxtonella sulcata in an unfavourable environment occurred by disruption of the endoplasm through the cytostome.

7. Buxtonella sulcata disappeared from faecal material at room temperature more quickly than balantidia from the pig, but withstood manipulation under the microscope better than the balantidia.

8. The passage of an individual between two obstructions suggested a means of intercellular tissue penetration by ciliates.

9. The oral plug and the centralised neuromotor system described and figured by McDonald in Balantidium coli could not be differentiated by the writer, but McDonald's other morphological observations on the above ciliates were confirmed.

Ten larval Cestodes, eight from aquatic and two from terrestrial hosts, have been described. Of these, eight species are new, and in the case of Cysticercus “A,” both larva and adult are new. By direct animal experiment the life-histories of three forms have been definitely established, while by careful comparison of the hooks of the scolex two larvae have been related to known adults. Cysticercus Hymenolepidis setigerae, previously recorded only from Copepods, is described here from an Ostracod host.

Effect of the parasite on the host. It is difficult to estimate the effect of Cestode larvae parasitic in Invertebrata, especially in the smaller forms such as the Entomostraca. In the latter, I have found that the intestine and musculature suffer most, and that the reproductive organs remain unattacked. The same remarks also hold for Oligochaete hosts. Dady (1901) considers that the influence of these cystic stages on their hosts is considerable, particularly on the musculature, sexual organs and intestine, and that death of the host may follow. Lindner (1921) states that little or no harm is done to Ostracods by the presence of tapeworm larvae, and also that the ovary of the female remains unattacked. The same author considers that, among the Entomostraca, destruction of the intestine occurs only in Copepods, the body cavity of Ostracods being so roomy that a harming of the intestine by growth of the parasite is unlikely. Schmidt (1894) finds that for Cysticercus Hymenolepidis anatinae, the host, Cypris ovata, was not particularly affected.

Among the Sporozoa inhabiting the gut of Scolelepis fuliginosa Claparède at Plymouth, I have often found an organism that I believe to be a peculiar coccidian, although certain important stages in the sexual part of the life cycle have hitherto escaped me. If I am right in my opinion, then this sporozoan is a new form, belonging to no genus of coccidian hitherto described: I propose for it the name Dorisiella scolelepidis.