This survey records the intestinal protozoa found in 611 hospital cases in Sweden, 1244 mental asylum cases in Sweden, and 159 medical out-patients in Finland. Only one examination was made of each case.

In each of these three groups the following protozoa were found: Entamoeba histolytica, E. coli, Endolimax nana, Iodamoeba bütschlii, Giardia intestinalis, and Chilomastix mesnili. In hospital and asylum cases in Sweden Dientamoeba fragilis was encountered, Trichomonas hominis and a small flagellate were found in the asylum group, and in this group as well as in the series in Finland, Balantidium coli was met with. In one case cysts of this protozoon were found.

In a group of 46 cases, formed stools as well as loose stools obtained after administration of a purgative were examined. The loose samples revealed the presence of Trichomonas hominis, Balantidium coli, and a small flagellate, none of these having been found in the formed specimens. The percentage of Dientamoeba fragilis rose from 8·7 per cent, in the formed stools to 23·9 per cent. in the loose stools. All the other species were more abundantly present in the loose than in the formed samples.

In Sweden, mental asylum cases show a much higher incidence of infections than do the hospital cases.

Intestinal protozoa seem to be more common in Finland than in Sweden.

Among hospital cases in Sweden the residents of Stockholm show a lower incidence of infections than do the people living in rural districts.

At admission, asylum cases are not infected to a higher degree than are the general hospital cases. The rise in incidence of infection is directly proportional to the length of time spent in the institutions up to ten years, after which time no further increase occurs. The male patients show throughout considerably higher percentages of infections than the female patients. Chilomastix mesnili shows a very high incidence in the asylums, whereas the percentage of Giardia intestinalis remains practically the same throughout the time of confinement in the institution.

In 1916 Dr J. C. Becker made the interesting discovery of Bilharzia infection in Physopsis africana collected at Nijlstroom in the Transvaal and obtained the adult flukes in some guinea-pigs he had exposed to infection with the cercariae. The town of Nijlstroom is situated at the source of a tributary of the Limpopo river at an altitude of 3924 feet above the Indian Ocean into which it flows. In 1917 I collected2 infested examples of P. africana at Magaliesburg, a popular picnic place for Krugersdorp residents, situated on a branch of the Little Crocodile river which later joins the Limpopo. Magaliesburg has an altitude of 5000 feet above sea-level. I also obtained infested examples from Rustenburg, thus revealing a further source of infection from tributaries of the Little Crocodile river, at an altitude of over 4000 feet.

The investigation deals in detail with the structure of the immovable and movable parts of the head of the Nycteribiidae. The muscles of the head are also studied.

The head capsule is modified from that of the Hippoboscidae. The vertex is not subdivided into several anatomically differing subregions. The occiput is represented by the border of the occipital foramen only. The postgenae are separated by the median membranous region of the head, as in the Hippoboscidae. The ptilinum serves as a flexible joint connecting the fronto-clypeus with the vertex and the genae. The fronto-clypeus is much more modified than that of the Hippoboscidae and is movable. The eyes are reduced to one or two facets, or are entirely absent. The greatly modified ocular sclerites are present in Cyclopodia only.

The antennae consist of the pedicle and the flagellum, the latter being concealed in the cavity of the former. They have the same structure as those of the Hippoboscidae parasitising birds.

The proboscis has much in common with that of the Hippoboscidae though it differs greatly in detail. It is composed of the rostrum, the haustellum and the labella.

The rostrum belongs morphologically to the head and is formed of the same parts as in the Hippoboscidae. All the parts of the rostrum, with the exception of the tormae, have the same arrangement as in that family. The tormae are separate and are attached at the lateral borders of the fronto-clypeus.

The haustellum is composed of the theca, the labial gutter, the labrumepipharynx and the hypopharynx. The two former parts belong morphologically to the labium, but differ in detail from those of the Hippoboscidae. The very short labrum-epipharynx is enclosed in the posterior part of the labial gutter.

The hypopharynx is very slender and as long as the theca; it is enclosed in the cavity formed by the dorso-lateral parts of the labial gutter.

Labial glands are present in the bulbous part of the theca; their ducts open into the food canal. All the muscles of the bulbous part of the haustellum are homologous with those of the same part of the proboscis of the Hippoboscidae.

The labella are entirely membranous, are armed with two inner and six prestomal teeth and their surfaces have serrated ridges. There are six gustatory sensillae on the membrane of each labellum, which are connected by the intralabial canaliculi with the sense cells of the bulbous part of the theca.

The cutting action of the teeth of the labella depends upon the protractions and retractions of the narrow part of the theca. When this part retracts it everts the inner membranous walls of the labella, and the teeth, being attached to these walls, perform protrusible divergent movements.

The two genera here considered agree with one another and differ from all the other members of the Lernaeopodidae in having the abdominal appendages dorsal to the eggstrings; and all their species so far described are parasitic upon some species of ray.

Parasitology, 20, 87. The legend to Fig. 7 should read: A 1. = antennules; A 2. = antennae.

The following report deals with a considerable collection of Nematodes made by Prof. A. S. Pearse, of Duke University, Durham, N.C., U.S.A., in various parts of Nigeria, and very kindly sent by him to the writer for study and determination.

Among Helminth material collected in the Sudan by the late Dr A. J. Chalmers, I have found some eight or nine mounted specimens of a Cestode, from the intestine of Gyps rüppelli, which has not, so far as I am aware, yet been described, and which apparently belongs to a new genus.

A few specimens very badly preserved and pigmented: coating them was a deposit which entirely obscured the internal anatomy and could not be removed. The internal anatomy therefore could not be removed. The internal anatomy therefore could not be elucidated. Length 10*, greatest breadh 0·47. Scolex 0·54 dia. As the only species without a rostellum recorded from this host is A. vaginatus the specimens are listed under that name.

The genus Crenosoma was founded by Molin in 1861 for two species of nematodes, Strongylus canis vulpis Rud., 1819, from the lungs of a fox (Vulpes vulpes L.), and Strongylus striatus Zeder, 1800, from the bronchi of a hedgehog (Erinaceus europaeus L.).

The modern history of the group of parasites of which this paper relates begins with the unfortunate publication on the same day—December 28th, 1899—of two simultaneous revisions of the Trematoda by Looss and Lühe, which has led to endless confusion and difficulties of nomenclature. In the present instance both writers described new genera under the same name—Telorchis—placing in each somewhat similar assemblages of species, yet not sufficiently close in character to be accepted as synonymous genera; at the same time each writer wisely selected a type species and thereby rendered the task of unravelling this knot in systematics very easier. The position will be at once apparent on comparing the two descriptions, and in order to facilitate this I have rearranged the translated clauses of each so that they appear in the same order: