1. The assumptions underlying the current methods of determining the efficiency of drugs or a mixture of drugs as an anthelmintic are set out.

2. The method of assessing the efficiency of a given drug or mixture of drugs, as used by Seddon and Ross, is cited and objections to its value are given.

3. A method is suggested whereby the mean efficiency of a drug or mixture of drugs can be assessed, in terms of the initial and residual infestation of selected animals.

4. In the light of the suggested method, Roberts' data for the efficiency of various drugs and mixtures of drugs, as specifics against H. contortus infestation in sheep, are fully investigated.

The author wishes to express his sincere thanks to Dr Shen Tseng of Shantung, Tsingtao, China, for supplying diagnostic characters of three species of Aploparaksis Clerc 1903. All measurements are given in mm.

Observations have been made on the survival of unfed rat-fleas, both newly hatched and wild-caught, under controlled conditions of temperature and relative humidity, and further observations on oviposition, hatching of eggs and emergence of adults under the same conditions.

The results show that, of the three sets of conditions employed, a temperature of approximately 20° C. and relative humidity of about 100 per cent. are the most favourable for survival of adults, hatching of eggs and production of a further generation of adults. The two other sets of conditions (temperatures of 15 and 30° C., with relative humidities of 60 and 100 per cent. respectively) are entirely unsuitable for the breeding of the species of fleas used.

At 20° C. and relative humidity 100 per cent. the whole pre-adult life of Xenopsylla brasiliensis and X. cheopis is, on the average, approximately 8–9 weeks, the minimum being 6 weeks. The female in both species is shown to have a distinctly shorter larval and pupal life than the male.

That part of the physiological life history of the tick, Ixodes ricinus, which is dealt with in the present paper, falls into three distinct phases: maturation of the gonads, oviposition, and development of the egg; these three are collectively referred to as “reproduction”.

1. A strain of Culex pipiens which is autogenous and stenogamic has been found at Hayling Island, England, and compared with British anautogenous strains.

2. Definite characteristics in adults of both sexes and in larvae have been found which separate the autogenous from the anautogenous British strains of C. pipiens.

3. The autogenous strain differs from the anautogenous strains in (a) the lighter colour of the thorax of the adults; (b) the greater average number of hairs on the ninth tergite of the adults; (c) the relative shortness of the male palps in comparison with the proboscis; (d) the larger average number of branches in each of the four siphonal tufts of the fourth instar larvae; (e) the lower siphonal index of the fourth instar larvae; and (f) the greater width of the egg relatively to its length.

1. Chilomastix from Bufo vulgaris has been grown in culture media but a “pure” strain was not obtained. Division and encystment occurred.

2. Two types of division were found. In one type the original cytostome and flagella persisted and a new set was formed from one pair of basal granules. In the other type the original cytostome disappeared and two new ones were formed from the two pairs of basal granules. This second type of division is similar to that of Chilomastix aulastomi from Haemopis sanguisuga.

3. It is therefore probable that two species of Chilomastix are present in Bufo vulgaris.

4. Cysts of Chilomastix from Bufo vulgaris and of Chilomastix aulastomi were studied. Nuclear division was never seen in them.

I wish to offer my best thanks to Mr Clifford Dobell, F.R.S., for kindly reading through the manuscript.

In October, 1934, several specimens of a tick belonging to the genus Ornithodoros were forwarded to the Bureau of Animal Industry for identification by Drs William Thompson and N. E. Dutro. These ticks were first observed by Mr F. E. Swan of the Bureau of Entomology and Plant Quarantine in a carload of bat guano originating at Linares, Mexico, and held in quarantine at Matamoros, Mexico.

An account is given of the preparation of Elford's gradocol membranes and their application in the study of plant viruses. The technique is discussed step by step and the chief sources of error are indicated. It is shown that plant virus suspensions clog the membranes, and suggestions are made for the preparation of those suspensions for filtration. The effect of virus content, purification and pH of virus fluids upon their filtration is discussed.

1. The distribution of the larvae of Simulium spp. in the River Tees area is discussed.

2. The dominant species of

(a) the upper Tees are S. monticola and S. variegatum;

(b) the lower Tees are S. equinum and S. reptansvar. galeratum;

(c) the Skerne is S. ornatum.

3. The causes of these differences are unknown, but it is suggested that geological structure, the distribution of water plants and the hardness of the water are important factors.

Many workers must have asked themselves whether a malaria parasite of bird or mammal has any harmful effect on the mosquito in whose body it grows and multiplies so remarkably; but though various opinions have been expressed, I cannot discover that any conclusive answer to this question has been given.

A Parasite which proves to be the cysticercoid of a Cestode was discovered by one of us (A. M. G.) in the course of work on the locust problem in British Chad in 1933–4. The material was sent to the Imperial Institute of Entomology, London, where the other author (A. G. H.) undertook the microscopic examination, measurement and description of the specimens and determined their nature. This is the first time a Cestode larva has been recorded in Acrididae and, as far as can be ascertained, in Orthoptera generally. The original slides have been deposited at the British Museum (Natural History).

1. Phaonia mirabilis eggs are laid on the surface of water in tree holes. The eggs are white and have lateral flanges and a ventral keel.

2. Trimorphism is absent during larval life, and, except for size, the newly hatched larva resembles the mature larva, having anterior spiracles, triforous posterior spiracles and complete buccal armature.

3. The larvae are carnivorous and capture and devour mosquito larvae.

4. Eggs hatch in 3–4 days. The duration of larval life is about 4 weeks and that of the pupal stage about 2 weeks.

In “A Brief Guide to the Varieties of Anopheles maculipennis” which was published in the Quarterly Bulletin of the Health Organisation of the League of Nations, 3, No. 4, December 1934, it is recorded that five varieties of this species are considered valid and that there is in addition the closely allied species—or a further variety— A. elutus. The provisional key to identification given in the Guide is based on the characters of the eggs of the different forms, but information on other characters is added in parentheses. It includes pro-visional information on the characters of the external spine of the harpago.

(A) Enteromonas hominis Fonseca, 1915 (emend. Dobell, 1921) is the correct designation of the flagellate first adequately described as Tricercomonas intestinalis by Wenyon and O'Connor in 1917.

Organisms morphologically indistinguishable, at all stages in the life-cycle, inhabit various macaques (M. rhesus, M. sinicus, M. nemestrinus). I have grown the simian species in “pure” cultures, and have obtained all stages in vitro and in vivo: and I have also obtained evidence—not “experimental ”, but from observed spontaneous spread of infection—that the species in M. rhesus and M. sinicus, at least, are identical.

An attempt to infect a man experimentally, by oral administration of cysts from a pure culture of the simian species (from M. sinicus), was unsuccessful.

(B) Embadomonas intestinalis [ = Retortamonas Wenrich nec Grassi] is probably the correct designation of the flagellate described by Wenyon and O'Connor (1917) as Waskia: and it is the only intestinal protozoon of Man which can be readily cultivated at all temperatures from 15° to 38° C. This species closely resembles several others described from other vertebrates—both warm-blooded and cold-blooded—but the identity of them all is still questionable.

A species similar to E. intestinalis has been observed in macaques by several workers, and has been assumed to be identical on insufficient evidence. Two attempts which I have made to infect macaques (M. rhesus and M. sinicus) experimentally, by feeding on cysts in pure cultures of E. intestinalis from Man, were completely negative.

(C) Consequently, while it seems probable on general grounds that both the Enteromonas and the Embadommas of men and macaques are specifically identical, it is still premature—with only negative evidence for their transmissibility from host to host—to assert this conclusion as a fact.

In 1892 P. J. van Beneden described and figured among some caligids from Africa and the Azores a new genus and species to which he gave the name Pupulina flores. He claimed to have found both sexes of the new parasite, but acknowledged that he had described as male and female of his species two copepods which had previously been designated by different names. They were found upon the same host, a devil-fish, and he believed that they were of the same species. In this, however, he was mistaken, for the specimen he described as the male was really a young female of an entirely different species. Owing to this mistake, together with the very imperfect description of both sexes, Bassett-Smith in 1899 denied the validity of the new genus and transferred Beneden's species to the well-known genus Lepeophtheirus. Following this lead the present author placed it in a key to the species of Lepeophtheirus published in 1905, and it has remained there up to the present time.