1. An account is given of Aproctonema entomophagum Keilin 1917, a Nematode parasite of the larvae of a Mycetophilid fly, Sciara pullula Winn., inhabiting decaying wood.

2. The life history of this parasite is remarkable in the following respects:

(a) The free-living stage is very short.

(b) Both sexes are parasitic.

(c) The usual host is the larva of the fly, from which the parasite escapes by actively breaking through the skin; but some parasites may be carried through to the imagines, from which they escape largely by the aid of the egg-laying movements provoked by them in the flies.

3. Metamorphosis of the Sciara larva is delayed by the parasitism, so that at least two generations of Nematodes may be found in one host.

4. All the parasitised imagines so far examined have been females.

5. The systematic position of Aproctonema is discussed, the conclusion being that this worm and its near relative, Tetradonema plicans Cobb 1919, represent two closely allied genera of the family Mermithidae, but are not synonymous with Mermis. It is proposed to dispense with the family Tetra-donematidae Cobb.

1. Accurate measurements were made of adults, larvae and eggs of Rhabditis pellio, representing an average selection for comparison with Johnson's figures.

2. The most satisfactory method of culturing the nematodes was in hanging drops, in a medium free from an excess of putrefying bacteria.

3. A medium poor in food was found to prolong life (up to 40 days), while a rich medium quickened up the life processes thereby causing death sooner. It is probably partial starvation which prevents the larvae from becoming mature while in the living earthworm.

4. In a medium favourable for prolonging life, the males were found to live about one-third as long as the females (F generation). It is probable that the females only live for about 4–8 days in a decaying earthworm after attaining maturity.

5. The maximum number of eggs laid per female was 257 (F generation) and 197 (F1 generation). It is probable that between 150 and 300 eggs are laid per female in the natural state. No information was obtained regarding the effect of the various media on egg production.

6. In most cases the females died when spent of eggs.

7. Vivipary is considered to be due to a favourable environment probably aided by a high temperature.

8. Larvae were found to be more susceptible to cultural conditions than the adults, especially those (F generation) which were not bred from females in culture media. The growth-rate of F1 generation larvae was found to be slightly faster in a natural medium, such as earthworm broth, than in peptone.

9. The chief food is considered to be bacteria.

10. During this work R. pellio behaved entirely as a bisexual species. A few cases of copulation were observed, showing that some of the males had not lost their “sexual instinct.”

11. Rhabditis pellio is considered to be a species in which hermaphroditism is just commencing and in which true males and females exist together with hermaphrodite females whose numbers fluctuate, the degree of hermaphroditism possibly bearing some relation to the sex ratio.

12. The sex ratio was about 1 ♂: 2 ♀♀, in both the F and F1 generations, but varied considerably. There were a few cases in which the male proportion was equal, or higher, than the female.

13. Four different species of British earthworms were examined, each being infected by Rhabditis pellio to a varying extent. Eisenia foetida was, however, rarely infected. Size of the earthworm, in proportion, played no part regarding the degree of infection. There is an indication that the head (segment I to the beginning of the clytellum) is the most heavily infected region.

14. A few specimens (larval stage) of an Ascarid, a species of Porrocaecum, a parasite of small mammals and birds, were found in three of the species of earthworms examined.

15. A probable course of the life history is given, based on this work and that of Johnson (1913).

Through the kindness of Dr S. W. Kemp, F.R.S., and of the Discovery Committee, the writer has recently had the opportunity of examining examples of a species of Uncinaria from the intestine of a sea-lion. These were collected by Mr J. E. Hamilton, of the Discovery staff, at Cape Dolphin in the Falkland Islands, in April 1931. The host was a sea-lion pup, about three months old, which was found dead on the beach, and it was suspected that the worms were concerned in the causation of its death.

1. The life history of Lecithodendrium chilostomum has been established; C. Lecithodendrii chilostomi penetrates a second intermediate host, the larva of Phryganea grandis, and unlike other stylet cercariae does not encyst, but feeds and grows in the host tissue as a mobile metacercaria. During pupation of the host in the following year these mobile forms migrate from the abdominal segments of the larva to the thorax, where they then encyst in the thoracic muscles in which they are also found in the imago. The largest metacercariae and the excysted worms are typical early adult Lecithodendrium chilostomum. No case of progenesis in the metacercaria was found.

2. It is estimated that the maximum swarming of the cercariae probably occurs during July, when first penetration of the intermediate host takes place. Subsequent diminished swarming and penetration proceed until November. The life of the larval trematode as a mobile metacercaria is approximately 8 months; the imagines of Phryganea grandis emerge during May and June, the infective period for the final host.

3. The metacercariae are not distributed throughout the body cavity of their larval host, but the majority are confined to the three posterior segments.

4. Limnophilus rhombicus may also serve as a second intermediate host, but the infection is very light and the metacercariae do not encyst during pupation of this host.

5. The excretory system has been determined in all stages of Lecithodendrium chilostomum; it is of the 2 (6 × 2) type. The occurrence of this type of system in other groups of cercariae is reviewed and since it is found in several widely separated families, it is suggested that its presence does not necessarily imply relationship, but is due to convergence.

6. The life histories of the following bat trematodes are indicated: Lecitho-dendrium lagena, Plagiorchis vespertilionis and Crepidostomum moeticus.

7. The life history of Dicrocoelium dendriticum is discussed.

On the skin of the dorsal surface, and particularly on the dorsal fins of Scyllium canicula at Plymouth, occurs a parasite which appears to be identical with Paracotyle caniculae Johnstone 1911. In British waters it was first noticed by Scott (1906) who queried it as a species of Epibdella. Johnstone (1911) gave an account of the species but his specimens were immature, being in the male phase of their development and considerably smaller than those found at Plymouth.

The present paper deals mainly with some new species of cestodes collected from birds commonly occurring in and near Nagpur, C.P., India.

The life history of Onesia accepta Mall. is described. This species is parasitic on the earthworm Microscolex dubius Fletcher. The first and second larval instars are passed under the skin and the third instar in the body cavity of the host. The feeding period of the maggot is approximately 20 days, and the pupal stage about 12 days.

The external morphology of the three larval instars and of the puparium is described in detail.

On March 7th, 1931, the writer collected numerous ticks (six species) from an adult tapir, Tapirella, bairdii (Gill), soon after it had been killed near Summit, Canal Zone, Isthmus of Panama. By far the greater number belonged to a species somewhat resembling Amblyomma cajennense in general appearance, but showing characteristics readily separating it from that species. Two young tapirs, of the same species as the foregoing, that were examined more recently were also found to be heavily infested with this species of tick. Since this species is apparently a new one it is herewith described under the name of Amblyomma tapirellum.

This paper contains an account of four new Coccidia from Uganda: Caryospora legeri sp.n., from a snake, Psammophis sibilans; Isospora dirumpens sp.n., from a snake, Bitis arietans; Wenyonella africana gen.n., sp.n., from a snake, Boaedon lineatus; and Eimeria urnula sp.n., from a bird, Phalacrocorax carbo lugubris. Eimeria dukei. Lavier 1927, is recorded from a new host, Chaerephon (= Nyctinomus) limbatus (bat).

The characters of the new Coccidia are summarised in the diagnoses (pp. 364, 369, 373, 378). There is a list of all the known species of Isospora found in snakes and lizards. It is noted that I. coelopeltis Galli-Valerio 1926, is actually an Eimeria, and its name is amended to E. coelopeltis. The diagnostic characters of the three species of Caryospora are given in tabular form.

The discovery of a new type of Coccidia, with oocysts containing sixteen sporozoites, divided between two sporocysts in Dorisiella Kay 1930, and between four in Wenyonella gen.n., necessitated a revision of the systematics of the Eimeriidea.

When the genera comprising this suborder (with a few exceptions) are arranged in the ascending order of the number of structural elements (sporocysts and sporozoites) contained in their oocysts, they form parallel series or groups in the horizontal and vertical directions, which consist of homologous members, as represented graphically in Fig. VI (p. 383). The oocyst characters of each genus are determined by those of its four neighbours in the horizontal and vertical groups.

This scheme serves as the basis for the new classification proposed, which is represented in Table III (p. 385). The higher systematic units (subfamilies) are distinguished from each other by the number of sporocysts within the oocyst, while the genera of each subfamily differ from each other in the number of sporozoites within each sporocyst, thus forming a homologous series.

Two species of coccidia have been found in captive Felidae examined by us in Russia:

(1) Isospora felis Wenyon 1923, in lion, tiger and lynx.

(2) Isospora rivolta (Grassi 1879), in tiger, leopard and jungle cat.

My observations on Lankesteria culicis, as it appears in Aedes albopictus in Calcutta, show that the trophozoites are intracellular in the anterior and extracellular in the posterior regions of the mid-gut, with epimerite rudimentary in the former and well developed in the latter condition. Full-grown forms measure 150–200 × 31–41μ. Association is lateral. Sporocysts measure about 10 × 6μ and are broadly spindle-shaped with slightly flattened ends, with a-residual body situated more toward one pole than the other.

Septate eugregarines in general, excepting the Stenophoridae Léger and Duboscq, grow extracellularly with the epimerite attached to the host cell. Therefore, judging from the foregoing description, we are no longer justified in retaining Lankesteria culicis among the Haplocyte gregarines (Acephalina) and in the family Diplocystidae Bhatia (1930). The presence of a well-developed epimerite and what I consider to be a rudimentary protomerite, clearly distinguish it from any of the Acephalina. Its place should be among the septate gregarines (Cephalina), and perhaps a new genus may have to be erected to receive it there.

The writers (1932) have previously reported on the surprisingly great individual variability in susceptibility to infection with Eimeria miyairii which they encountered among white rats taken at random. It was learned in the study that young rats of from 65 to 149 g. in weight would eliminate from 14 to 169 million oocysts during immunisation produced by inoculation per os with 1500 sporulated oocysts daily over a period of 5 days. The question naturally arises whether different strains of the host exhibit differences in susceptibility similar to those noted in individuals.

In 1930 Ray published a valuable paper on the genus Selenidium Giard, in which he described sporogony in S. spionis Koll. and S. foliatum Ray. He did not observe schizogony in either of these two, but he confirmed Brasil's account of intracellular schizogony in S. caulleryi Brasil from Protula tubularia Mont, and recorded it for the first time in S. mesnili Brasil from Myxicola infundibulum Mont. After seeing association of gametocytes in both these species he was unable to continue his observations, so I have taken up the work where he left it, choosing S. mesnili rather than S. caulleryi, since it is more easily obtainable. My search for gamete and sporozoite formation has been successful, but I have not been able to make the sporozoites hatch, or in studying sections of Myxicola have I seen sporozoites entering the epithelial cells of the gut.

This volume, p. 252, line 16, for “Jajonetta n.g.” read “Ceratotrema n.g.”