The classification of the nematodes occurring in the lungs (and related forms) of land mammals has always been one of considerable difficulty, in large part because of the existing very inadequate descriptions of many of the commoner forms. Most systematic helminthologists have followed and amplified the classification adopted by Railliet and Henry in 1907, a system which divided these nematodes into three main groups — those found in the blood-stream (Hæmostrongylus); those found in the larger bronchi (Dictyocaulus, Metastrongylus and Crenosoma); and those found in the minute bronchi and alveoli (Synthetocaulus). While the first two groups contain four well-defined zoological species, an examination of the forms included in the genus Synthetocaulus shews that it consists of a heterogeneous collection of species, which, although possessing a common habitat, are by no means so closely related as has been supposed, and, indeed, belong to several different genera.

A Preliminary outline of the life history of the lungworm of the cat and its confusion with that of Ollulanus tricuspis, has been given in a previous paper. Since that paper was published, the name of the family of lungworms has been changed to Protostrongylidæ by Professor Leiper; and an examination of adults of the lungworm from the cat, shewed that it belonged to a different genus from the type of the old genus Synthetocaulus. To this new genus, the name ælurostrongylus has been given.

While carrying out an intensive survey of the helminths parasitic in domestic animals at Aberystwyth, an opportunity was Afforded the writer to examine the dogs and cats taken to the local police station for destruction by the lethal chamber process. These animals comprised the unclaimed “strays,” the incurably wounded or maimed, the vicious and the aged. Healthy but unwanted animals, also, were occasionally destroyed.

Although it was known that certain diseases of domestic animals in wales were caused by parasitic worms, the systematic study of the economic importance of these worms did not begin until 1874, when Dr. Cobbold and a Mr. Rees Lloyd from Brecon investigated the “disastrous epizoöty” in the case of welsh mountain ponies.

Until recently, it had generally been accepted that the life history of Ollulanus tricuspis was a complicated one involving an intermediate host, the mouse. Last year, however, I drew attention to the fact that the larval stages, both in the cat and in the mouse, believed by Leuckart to belong to Ollulanus, were really those of Ælurostrongylus, the lungworm of the cat. Subsequent work has enabled some of the details of the life history of Ollulanus to be elucidated—although by no means all—and these are considered in this paper.

This eelworm, only just visible to the naked eye, and quite common in vinegar in all parts of the world, has long been known to zoologists, and indeed was an object of keen interest and discussion to the naturalists of the seventeenth century. Petrus Borellus [3], for instance, enthusiastic over the recent adoption of the microscope for researches in natural history, published in 1656 his “Observationum Microcospicarum Centuria,” in which he leads off with a note “De Vermibus aceti.” In the twelfth edition of the “Systema Naturae” (1767), Linnaeus included a species redivivum in that final genus of the Regnum Animale so appropriately named Chaos. This species of animal he says, “Habitat in Aceto & Glutine Bibliopegorum.”.

Free-living nematodes commonly occur in cultures of fæces, and as Looss (1911) showed years ago they have frequently been mistaken for the developmental stages of parasitic nematodes. For this reason it is important that detailed knowledge of the morphology of such free-living forms should be available. With this end in view the following illustrated account of what appears to be a new genus of nematode has' been prepared. The worms occurred originally in a culture of the fæces of a brown rat, Rattus norvegicus, made for the study of the free-living stages of the Strongyloides of the rat; and as after detailed study it has been found impossible to find any existing description of nematodes which agree with the structural appearances shown by the worms, it has been decided to create a new genus for their reception.

In the extensive literature devoted to this worm axe many anatomical descriptions, the earlier of which are, according to modern standards, vague and superficial. But among recent authors de Man (1910) has given a full and illustrated account with detailed measurements of some forty specimens, an account to which it might seem difficult to add anything of importance. However, the present writer is preparing a paper on the bionomics of the worm, and therefore considers a brief anatomical description to be desirable, particularly as de Man's paper may not be easily accessible to those interested

A Considerable number of specimens of this parasite were collected from the small intestine of a genette which died in the Gardens of the Zoological Society of London.

The cuticle of the cephalic extremity is dilated anteriorly. This swelling is terminated posteriorly by the cuticle incurving to meet a raised ring on the body-wall, about the level of the junction of the anterior and second fifths of the œsophagus. There are no cervical papillæ present, and it is probable that this ring may be regarded as replacing them. Just anterior to the middle of the œsophageal region and at the level of the excretory pore is a cervical groove which completely encircles the body. Laterally the cuticle on the anterior margin is thickened; it is also thickened on the ventral side, but less so than laterally. These thickenings are reinforced by a granular inclusion in the cuticle. The posterior margin is thickened only in the region of the excretory pore.

During the pursuit of field work in the neighbourhood of Warwick in which the collection and examination of insects was involved, it was observed whilst carrying out dissections of dung-infesting beetles that several of them had attached to various parts of the exoskeleton collections of what were at first taken to be fungus spores. On close examination, however, these adherent bodies were discovered to be encysted nematodes which were using the beetles as carrying agents, whereby their transference to fresh dung, required for further development, would be assured.

Our attention was drawn to a short note, written by Christie (1925), in which this author discusses the finding of what was either Rhabditis coarctata Leuck. or a closely related species on a number of species of dung beetles in America. With this information in mind, it was decided to culture the worms in order to follow out the life-cycle, determine the species, and make observations on the behaviour of the nematodes in relation to the insects on which they were found attached.

It is well known that free-living nematodes are of frequent occurrence in various kinds of rotting organic materials both animal and vegetable under natural conditions. In a recent investigation of the nematodes occurring in a variety of substances such as pig-manure, sheep droppings taken from pastures, soil from a chicken run, decaying leaves from a drain, etc., the writer has made use of the Baermann method (Cort and others 1922) with a good deal of success. Amongst several interesting forms obtained from samples taken from a heap of pigmanure were six worms, four females and two males, belonging to the genus Aphelenchus, which at once attracted attention by reason of certain peculiarities in their appearance. They closely resemble Aphelenchus tenuicaudatus de Man (1895) in certain anatomical features, but differ on certain points, and the writer regards them as belonging to a hitherto undescribed species.

This small species of Ankylostome worm was found in the small intestine of a golden cat (Felis temmincki) from Sumatra, in association with numerous specimens of Ancylostoma caninum, A. braziliense and Strongyloides sp. It has been experimentally transmitted to the domestic cat.

The cuticle shews not only transverse striations but numerous very fine longitudinal striations.

Like Ancylostoma, the body shews a distinct longitudinal torsion, and when the dorsal aspect of the cephalic opening is facing upwards, the posterior extremity is displaced laterally. The body is narrowed anteriorly, terminating in a pyriform buccal capsule which, as in Ancybostoma, opens dorsally. The anterior end does not form a hook– like bend as in Necator and forms allied to it.

This paper forms a preliminary account of the occurrence of some helminths parasitic in sheep and pigs in South-Eastern England. The rocks of the Wye district are mainly Cretaceous, while Romney Marsh, with its extensive sheep population, is alluvial. Earlier workers have already considered certain helminthic parasites of this region. The present writer uses Morgan's technique. Thirteen helminths parasitic in the gut of sheep and lambs are listed with notes, and a record is made of some other observations, including the identification of Ascaris lumbricoides and Œsophagostomum dentatum from swine.

The classification of the Trematode family Opisthorchiidæ presents some difficulties to the systematist. These difficulties arise partly from the fact that a number of the existing species appear to lack any real morphological characters by which they can be differentiated, slight variations in measurements, together with a difference in host, having been considered sufficient to justify the making of new species. This view has resulted in the placing of undue importance on somewhat minor differences when they do occur in other species, such differences being considered sufficient for creating new genera.

The systematist is further confronted with the difficulty of forming definite opinions on the systematic position of some of the species made by earlier workers. Their descriptions and figures are often inadequate owing to the fact that characters which, in the past, were considered of minor importance are now given much closer attention. Examples of the confusion which has arisen from such a position will be referred to in this paper.

A certain amount of confusion still exists as to the terminology to be adopted in discussing the various stages in the life cycle of the nematoda. This appears to be largely due to a difference of opinion as to the termination of each stage.

After a larva has reached a certain size, it commences to change in form and completes this process by shedding its cuticle. This change in form is the lethargus. It may or may not immediately escape from the cast cuticle, but when it does, the ecdysis is complete. The form which emerges is morphologically identical with the form inside the cuticle after the completion of the lethargus.

This accordingly gives a double choice as to the exact end of the stage. It may be during the lethargus, when the morphology of the form is changing, or it may be at the moment when the larva leaves the cast cuticle. The interval between these periods is slight in some cases but is considerable in the case of the infective stage. As the physiological end of the stage seems to coincide with the lethargus, I have accordingly based my nomenclature on it.

This description of a new species of Paraspidodera is based on material from the Helminthological collection of the London School of Hygiene and Tropical Medicine which was handed to the writer for examination by Professor R. T. Leiper, F.R.S. The parasite had been collected by Dr. Sells from the wild pig in Uganda; no indication of the habitat is given. The writer wishes to thank Professor Leiper for placing this material at his disposal.

Hardy (1850) gave a description of some eelworms occurring in leaf-galls on the grass Festuca ovina and named them Vibrio graminis.