Bowl Of Water Research Articles

On the Effect of DDT-treated Surfaces on Adults of Anopheles gambiae and A. funestus

1. Certain experiments intended to throw light on problems arising from the practical application of DDT against A. gambiae and A. funestus are recorded. These refer particularly to the action of larvicidal DDT on adult mosquitos; to the effect of varying periods of exposure; and to the possibility of repellence of adults by DDT treatments.(a) Solutions of DDT on water surfaces produce an appreciable mortality, particularly on laying mosquitos, but also on ♀♀ in earlier stages of ovary development, when confined in cages with a bowl of water so treated.(b) The greatest effect is produced by a DDT solution in a heavy oil film of long persistency.(c) The presence of a DDT solution on the water, particularly when applied in a heavy oil, appears to have produced an appreciable inhibition against laying.3. With a 5-months-old residual film of 200 mgms. DDT per sq. foot on smooth wood, a 60-minute exposure killed 22 per cent. immediately and 100 per cent, within 3 hours. After a 5-minute exposure none was killed immediately, but 17 per cent. were dead within 3 hours, and 73 per cent. at 12 hours. Intermediate periods of exposure gave corresponding results.4. Anopheles exposed in inter-connecting treated and untreated cages showed characteristic restlessness as a result of contact with a treated surface. When inserted first into a treated cage, and subsequently allowed access to untreated cages, a higher mortality was recorded than when the procedure was reversed. The degrees of mortality and of restlessness appeared to be closely connected.

Studies on Aedes aegypti Infected in the Larval Stage with the Virus of Yellow Fever.

During the course of general transmission studies with Aedes aegypti, it became of interest to see whether these mosquitoes could be infected in the larval stage, and retain the infection into adult life. To this end, half-grown larvae were placed in a bowl containing a mixture of blood serum from a Rhesus monkey at the height of infection with the Asibi strain of yellow-fever virus, and an equal quantity of physiological salt solution. This was shown, by titration in mice, to contain 30,000,000 minimum lethal doses for mice per cc Pupation commenced after 48 hours. The pupae were washed and suspended individually in tubes of clean water, and the adults began to emerge 4 days after the first contact with the virus. The first 28 males to emerge were ground up and injected into a Rhesus monkey subcutaneously on the day of emergence. The monkey responded 4 days later with fever, and had virus in its blood stream. It was killed when moribund on the sixth day. Necropsy findings, both macroscopic and microscopic, were typical of yellow fever. Four days later, 15 females, varying in age from one to 4 days, were fed on a normal Rhesus, but failed to infect it. However, 10 days later 29 females from the same lot were able to produce yellow fever by bite in another Rhesus monkey. To confirm this observation, half-grown larvae were again placed in 50% serum from an infected Rhesus, This mixture was shown to contain 7,600,000 M.L.D. for mice per cc. In order to prevent the mosquitoes from pupating in the viral suspension, the larvae were washed 3 times in water at the end of 24 hours, and placed in a bowl of clean water.

Nutritional Value for Planarian Worms of Vitamin Depleted Mammalian Tissues.

The planarian worm has proved itself a useful instrument for demonstrating changes in the composition of mammalian tissues resulting from changing conditions in the animal as a whole. (Bahrs.) This research was undertaken to ascertain what the planarian worm could reveal as to modification of the nutritional value of tissues derived from animals fed diets with and without the recognized vitamins. Guinea pigs and white rats were used to furnish the tissues. The animals received standard basal diets for a month or more. (For diets used, see Table I.) When definite signs of vitamin A deficiency and polyneuritis were apparent in the respective groups of rats, the planarian worm experiments were started. Guinea pigs showed definite signs of scurvy before their tissues were used in the planarian worm experiments. The guinea pigs maintained upon the vitamin D-free diet, of course, appeared entirely normal when their tissues served for the planarian worm diets. Each group of planarian worms (probably Planaria agilis) consisted of 30 newly regenerated worms, all of the same length. Experimental groups were kept in finger bowls of heat-sterilized river water, and maintained at a constant temperature, 23°C-24°C. The worms were fed twice per week on thoroughly mashed tissues of freshly killed guinea pigs or rats, taken from groups fed the specified vitamin diets. They always ate the tissues well. Spleen, lung, liver, heart and in one case kidney cortex were the tissues used.

XIII. Bakwiri, British Cameroons

Witches are people believed to possess invisible powers, that nobody can explain, to do harm to others. This power is said to be in the heart of one so accused and it is not quite certain whether he knows of it himself. To prove that one is a witch or wizard the root of a certain herb (pwave) is mixed with water in a bowl and given to one to drink of it. If he does not vomit he is said to be a witch, but if he does he is not a witch.

AN ANALYSIS OF THE SPAWNING HABITS AND SPAWNING STIMULI OF CUMINGIA TELLINOIDES

1. The spawning season of Cumingia extends from the middle of June until the middle or end of September. The most active spawning usually includes the last week in June and ends about August 20. Each female spawns more than once and the production of gametes is practically continuous.2. The spawning is heaviest from full moon to new moon and least at first quarter thus showing a lunar periodicity.3. Cumingia is greatly affected by shock and rough treatment so that sexually mature individuals spawn promptly when brought to the laboratory, after being placed in a bowl of quiet sea water.4. There are apparently no chemical stimuli by which the sexes stimulate each other to sexual activity as is the case in Nereis limbata and the oyster. They spawn as readily when isolated as when in close proximity.5. It is shown that temperature is not the only factor which determines the duration of the spawning season and periods of spawning.

The life-cycle of cladocera, with remarks on the physiology of growth and reproduction in crustacea

In a paper on the life-cycle of Moina rectirosiris , published in 1913 (5), it was shown by the late Mr. G. H. Grosvenor and myself that it was possible to inhibit entirely the production of the sexual forms by isolating the parthenogenetic parents soon after birth, and keeping them at a constant high temperature of 25-30° C. It was proved that for a succession of eight generations the isolated parents at this temperature gave no males or ephippial females, while parents of the same generations kept crowded at a temperature of about 14° C. or 5° C. gave about 50 per cent, males. We were unable to determine how the effect of isolation and crowding of the parthenogenetic parents influenced the production of the sexual forms, but two alternative suggestions were made, either that in the crowded glasses the animals were unable to obtain sufficient nutriment and were partially starved, or else that some excretory matter accumulated in the crowded glasses which influenced the production of males and sexual females. In order to confirm the above results and to throw some light on the processes involved, breeding experiments have been carried on for some time with another species of Claclocera, the common Daphnia pulex. Mr. Robert Gurney very kindly gave me some dried mud from a pond winch was known to contain the resting eggs of these animals, and, on placing the mud in a bowl of water, after some weeks some young Daphnia hatched out. One of these was kept until it had produced young, and the offspring of these young ones were used to start the first experimental generation.