Two species of the genus Stephanochasmus have been found in the fishes examined for parasites at the station of the Carnegie Institution of Washington, situated on the island of Tortugas in the Gulf of Mexico. These are S. casus Linton and S. sentus Linton. The anatomy of these worms contains several novel and interesting features, and that of the first named will be described here in detail.

The incidence of Helminthiasis at Mombasa is herein briefly dealt with chiefly in tabular form. The tables give the result of the first 100 examinations conducted on natives of indigenous races complaining of intestinal troubles, admitted into or attending hospital.

(1) There is very little, if any, abnormal destruction of erythrocytes in cases' of infection with East Coast Fever. This is proved by blood counts, haemoglobin estimations, and the condition of the bloodforming and blood-destroying organs, all remaining practically normal. This is in marked contrast to what obtains in piroplasmosis.

(2) The hypothesis advanced by Nuttall fits all the facts. According to this hypothesis the invasion of the corpuscles occurs in the internal organs where the parasites develop, and the corpuscles only act as carriers of the parasites in the blood, thereby conveying them to the tick which serves as the vector.

(3) Since few, if any, of the corpuscles are destroyed they rapidly become charged with an increasing number of parasites which are being continuously produced in the internal organs as evidenced by Koch's blue bodies which form and break up in the lymphatic glands, spleen, liver, bone-marrow, etc. (Gonder, Nuttall).

(4) There is a marked leucopenia in East Coast Fever, the polymorphs decreasing less rapidly than the other elements. This is in contrast with the leucocytosis observable in piroplasmosis.

Consideration of the outbreak of fever at Morib in Selangor, Federated Malay States, impresses us with the great practical importance of obtaining an exact comparative infectivity table of the various anophelines, compiled on a comprehensive basis; it is only by accurate study of a disease and the factors responsible for it, that it can be successfully combated.

At Morib we can only rely on general considerations and conclude that the species ludlowi has been causing most of the trouble.

It would seem that the reason that hill-land malaria in Malaya, and perhaps India, is so difficult to get, rid of is because it is conveyed by mosquitoes of high infectivity and low prevalence, whereas low-land malaria can be easily allayed because it is conveyed by mosquitoes of low infectivity and high prevalence. It is a corollary to this that if malaria in any community can be easily allayed, it is caused by mosquitoes which possess low infectivity.

A fertile source of error in protozoology is to be found in the overlooking of the occurrence of mixed infections in a host. Two organisms, each independent of the other, may happen to coexist in the intestine of an insect or the blood of a vertebrate, the result being that the investigator may confuse stages in the life-cycles of parasites which are not related to each other. This source of error has led to unwarranted generalisations which have impeded scientific progress for years. Two examples at once come to mind—the trouble wrought by Schaudinn in 1904 in confusing the life-cycles of the protozoa found in the little owl, and the impediment put in the way of progress by the omission of certain workers to recognise that Crithidia grayi was not a part of the life-cycle of a trypanosome. The existence of mixed infections was overlooked in each case.

I was much interested in the paper on Herpetomonads in mice in the June number of Parasitology (Fantham and Porter, pp. 128–132). In 1904 or 1905 when working at trypanosomiasis at Khartoum I came across a flagellate in the peripheral blood of a gerbil (Gerbillus pygargus) which was clearly not a trypanosome and the nature of which I was unable to identify.

Habitat and Record. The animal under consideration, a parasitic member of the Copepoda, and belonging to the family Lernaeopodidae, occurs commonly on the males, and much less frequently on the females, of Scyllium canicula. The point of fixation is just outside the cloaca, between the pelvic fins, the parasite remaining attached permanently by the second maxillae to the tissues of the host, and occasionally even to the claspers, on their sides, preferably in the groove. I have several times found as many as six specimens on one host (Fig. 1), while three or four is a usual number.

Introduction. In a previous paper (1914, p. 217) I gave, in tabular form, the features which serve to distinguish the two genera Calliobdella van Beneden and Hesse 1863, and Trachelobdella Diesing 1850, which Johansson 1898, pp. 672–675 has also given reasons for distinguishing.

Female (Fig. 1): Colour: scutum, basis capituli, coxae, distal parts of femur and proximal portions of tarsi and intervening articles are blackish brown, the remaining hard parts shading to yellowish-brown. (Dorsal aspect) Body (partly gorged) short and broad. Scutum about as long as broad, 0·87 × 0·85 mm., very slightly emarginated, with rounded scapular angles, antero-lateral borders almost straight, lateral angles situated at the anterior third of the length, posterior border rounded; cervical grooves deep, far apart, but slightly concave outwardly and slightly divergent, fading near the postero-lateral borders; surface glossy, somewhat rugose; punctations few, mostly fine. Capitulum with base roughly equilateral-triangular, short pointed cornua and sinuous dorsal ridge; porose areas not depressed, subcircular, near ridge, the interval less than their width and hollowed. Palps slender, article 1 small, articles 1–2 almost fused, broadest at the distal third of article 3 which is rounded distally; (Ventral aspect) hypostome club-shaped, 4|4 merging to 3|3 and 2|2 posteriorly where the median unarmed ridge broadens, teeth sharp, 12 per external file; basis capituli constricted where the short pointed recurved auriculae arise, posterior margin straight with rounded angles. Venter: vulva between coxae II; anal grooves form a small closed ring situate near the posterior border; spiracle ovoid, macula central. Legs slender; coxa I with short internal and stout external spur; stout external spurs on coxae II–IV progressively decreasing in size; trochanters with slight spurs; tarsus 4 tapering gradually, the distal pseudo-article about thrice as long as the basal; pads large but shorter than the claws.

This communication is the first of a series dealing with Mallophaga from Australian marsupials. We had hoped to prepare a single monographic work on the Family Boopidae, but the carrying out of this plan has been prevented by a variety of causes, and we think it advisable to publish piecemeal the notes and descriptions that we have accumulated during the last six years. There has of late years been a recrudescence of interest in the Mallophaga, and a considerable number of students are now investigating the group. Little has been published upon the very distinct family which is characteristic of Australian marsupials, and it is important that students of the group should have diagnoses of the family, sub-families, and genera, based upon an ample material, which includes all the known species, with a single exception, and more than an equal number of undescribed new forms. Such a material is at our disposal. Apart from our own collections, Mr A. S. Le Souëf has very kindly transferred to us all his Mallophaga from marsupials, including his types.

An examination of a considerable number of specimens of larval Ascarids from the peritoneal tissues of marine fishes has led me to the conclusion that the great majority of these young nematodes are referable to a single species, Ascaris capsularia Rud. The older descriptions of this form are inadequate and superficial, and even by the more recent writers it appears to have been assumed that, as a larval form, it was impossible, or not worth while, to define it more precisely. I believe, however, that by paying attention to the internal structure it is possible, even at this early stage, to discover characters of specific importance. The imperfect recognition of these characters has led, it appears, to considerable confusion, and to the inclusion in the species of some forms which should be regarded as specifically distinct. A full synonymy and bibliography has been given by Stossich (1896, pp. 55–57) and it is unnecessary here to review the literature in detail. It is desirable to point out, however, that some even of the comparatively recent descriptions intended to refer to A. capsularia seem, in reality, to belong to some other form. Thus É. Blanchard (1849) describes and figures under the name of A. salaris a small form, 20–35 mm. in length, having three lips already visible, a lateral caecum at the base of the oesophagus and female genital organs already developed.