A consideration of the tick-activity data for South Wales reveals that there are usually two peaks of female activity in this region, one occurring in spring, the other in autumn. On an experimental area, divided into eight plots, on the Margam Moors, Glamorgan, significantly varying population levels are present on the different plots, although the peak of activity on all of them is attained around the same period. The seasonal activity of the nymphal and larval forms in South Wales is essentially comparable to that recorded by Milne (1945a) in the north of England. There is reason to believe that in mid-Wales a single summer peak of tick activity exists.

The engorgement period of female ticks on cattle varies from 7 to 13 days. The tick shows a distinct preference for the hind region of cattle for feeding purposes. The differences in the mean populations of ticks on different breeds of cattle are not statistically significant, at least, on the six breeds tested in 1944 and 1945. In the case of cattle, tick density and fecundity of the female are not correlated with the physiological condition of the host.

In South Wales, the populations of ticks on sheep are significantly lower than those on cattle, even where both hosts are pastured on the same ground for similar periods. The seasonal activity of female ticks on horses follows the same general trend as that noted on cattle.

1. Chickens were infected with Coccidia, considered to be Eimeria meleagridis, from turkeys.

2. Turkeys were subsequently infected with oocysts obtained from the chickens.

3. Slight variation from normal measurements of the coccidia in chickens is attributed to development in an abnormal host.

4. E. acervulina from chickens was not infective to a coccidia-free turkey chick.

The two filarial Nematodes known to parasitize dromedaries in Egypt are Dipetalonema evansi and Onchocerca fasciata, of which the first is the more common. Representatives of these genera also infect man and other animals and are known to be very common in endemic areas. Doubt has always arisen in the researches of those few who worked on this subject, as to the connexion of the adult Dipetalonema evansi with the microfilariae found in the blood of Camelus dromedarius and C. bactrianus.

In an earlier paper (1933) the writer drew attention to the inadequacy of the only existing description of Uncinaria lucasi, given, under the name of Uncinaria sp., by Stiles & Hassall (1899). Through the kindness of Dr E. C. Dougherty, it has now been possible to examine specimens of an Uncinaria from the type-host of U. lucasi (the Alaskan fur-seal, Callorhinus alascanus). These were collected by Dr V. B. Scheffer, of the United States Fish and Wildlife Service, from the small intestine of a furseal pup at Polovina, St Paul Island (Pribylov group), in the Bering Sea in July 1945. There seems to be no reasonable doubt that they are of the same species as those originally described by Stiles & Hassall, the principal evidence being the identity of the host and locality, and the length of the spicules of the male worms. A new description is therefore presented, which it is hoped will place the species on a more satisfactory footing.

The material used for the following description consisted of three worms obtained from the intestine of the oystercatcher, Haematopus ostralegus occidentalis Neumann, shot near Aberystwyth. This is the first record of a protogynous tapeworm from Britain. In the whole of the Cestoda the protogynous condition is known only in four other genera, namely, Progynotaenia Fuhrmann (1909), with six species, and Proterogynotaenia Fuhrmann (1911), Leptotaenia Cohn (1901) and Gynandrotaenia Fuhrmann (1936, 1936a), each with a single species. The six known species of the genus Progynotaenia have been recorded from Egypt and the White Nile, Proterogynotaenia rouxi Fuhrmann from the Aru Islands off the coast of New Guinea, Leptotaenia ischnorhyncha (Lühe) from the Mediterranean and Gynandrotaenia stammeri Fuhrmann from Germany.

1. When sporozoite-induced infections of Plasmodium relictum are treated with atebrin (mepacrine) in doses suppressive to blood-inoculated infections, for periods exceeding that of normal incubation, parasites devoid of pigment appear in the erythrocytes of the peripheral blood. A small proportion of these may develop into schizonts, but the number of merozoites produced is fewer than normal.

2. A similar phenomenon occurs when quinine is substituted for atebrin, but the drug appears to be excreted more rapidly so that the inhibitive effect upon growth is less marked.

3. When plasmoquine is given in the maximum tolerated dose to birds infected with sporozoites, parasites are not seen in the peripheral blood during treatment, though the infection is not sterilized. With smaller doses parasites, including a few small schizonts, are found in the erythrocytes during treatment.

4. Merozoites produced in the erythrocytes during drug treatment are not capable of further multiplication when inoculated into uninfected birds having a similar blood-concentration of drug, so long as treatment continues, though they develop normally when transferred to untreated birds.

5. No indication of drug resistance has been observed.

6. The possible mechanisms by which blood-inoculated infections are eradicated, or resist eradication, are discussed.

We wish to thank Miss Vincent (Mrs Thorpe) and Dr Parr Tate for access to their preliminary unpublished experiments, and the latter for helpful criticism.

(1) Ecdysis of the infective larvae of Trichostrongylus retortaeformis was induced by the action of pepsin.

(2) Exsheathment occurred by the loss of the anterior cap.

(3) pH 4−5 is shown to be the most favourable pH for eedysis and survival. This pH is within the range quoted for the stomach contents of rabbits.

(4)Eedysis was complete in the majority of larvae after 60 hr.

The plerocercoid larvae of the pseudophyllidean cestode Ligula intestinalie have been removed from the body-cavity of the roach, Rutilua rutilus, and cultured in vitro under aseptic conditions, using a technique similar to that successfully applied to Schistocephalus solidus.

In the larval condition, the genitalia are in a primitive, immature condition, with the testes, ovaries and yolk-glands only partially developed.

Larvae were cultured in peptone-broth in plugged tubes at a temperature of 40° C, i.e. the body temperature of birds in which the plerocercoids normally develop into adult worms.

Three of the nine larvae used became sexually mature after 7 days' cultivation, and oviposition took place. Copulation between successive genitalia of the same worm or with genitalia of another worm in the same culture tube was not observed.

Histological examination revealed that spermatogenesis, oogenesis, vitellogenesis and shell formation had apparently taken place in a normal manner. The testes contained giant polyploid cells as well as mature spermatozoa. The receptaculum seminis contained no spermatozoa, from which it was concluded that fertilization had not taken place. This was confirmed by the fact that attempts to hatch out the eggs were unsuccessful. The unfertilized eggs, however, underwent parthenogenic development within the uterus as far as the two-cell stage. Of the remaining six larvae, four developed sufficiently to undergo eversion of the cirrus, but died without oviposition taking place.

Four specimens of the pika (Ochotona rufescens Gray) were captured, and on dissection three of them were found to be heavily infested with a Nematode worm in the large intestine.

1. Stained specimens of two forms of a ciliate parasite resembling Lambornella stegomyiae Keilin which is probably Glaucoma pyriformis Ehrenberg are discussed. These were collected from the haemocoel of culicine mosquito larvae at Livingstone, Northern Rhodesia. The form previously referred to as type A (Muspratt, 1945) is the fast multiplying form which destroys the larva and that referred to as type B is considered to be either an encysting or degenerate form.

2. In nature the larva of Aëdes (Finlaya) fulgens Edw. is the most suitable host of the parasite because the normal (type A) parasitic ciliates are dependent on escaping from the larval host before death by the rupture of the anal papillae. This occurs most frequently in parasitized larvae of the above species.

3. The encystment of the organisms on the cuticle of the larvae is discussed with reference to statements by previous workers. Stages in the penetration of the cuticle by the organisms and the formation of cuticular resting cysts have been observed.

4. Larvae of A. aegypti used in laboratory experiments proved to be unsuitable as: (a) The anal papillae do not rupture easily. (b) After some time the reproductive power of the ciliates degenerates if they are transmitted from larva to larva of this species only.

5. Attempts to destroy anopheline larvae with the parasite were negative although the ciliates entered the haemocoel.

6. A suggestion as to the possible life-cycle is appended in the form of a diagram.