disease, which they say is a minute bacillus forming colonies smaller than a human red blood corpuscle. The results of this discovery should be of great practical importance.

Levaditi and his colleagues have now shown that Encephalitozoon cuniculi, the first microsporidian proved pathogenic to mammals, is transmitted through the digestive tract. They suggest that hydrophobia may be due to an allied organism.

Besredka's heretical views on local immunity to infectious diseases have been taken up by the Health Section of the League of Nations, which is proceeding to carry out an investigation on a large scale in cases of cholera outbreak in Russia.

Professor MacLean delivered a discourse on insulin at the Royal Institution, and pointed out that "the evidence available at present suggests that the pancreas forms another hormone essential for the process of normal carbohydrate metabolism besides insulin, and unless this hormone is present, insulin alone will not sustain life for a long period."

Carrel, of the Rockefeller Institute, opened a discussion at the annual meeting of the British Medical Association at Bradford, on the method of tissue-culture and its bearing on pathological problems. De Beer has published a book on "Growth," written for the general public, which should prove a useful introduction to the experimental study of tissuegrowth; and, for the specialist, there are this year two useful works by Strangeways on the technique of tissue-culture in vitro.

The prevailing shortage of cotton is partly due to the ravages of the pink boll-worm. The work of Williams, who has published an account of the entire life-history of this moth, should do much towards making effective legislation possible in cotton-growing districts.

Plant pathology has probably made greater progress during the last ten years than has any other branch of botany. In his presidential address to the British Association (Agriculture Section), Sir John Russell pointed out that the best hope for the future lies in the combination of empirical and scientific methods. Mycologists from all parts of the Empire met in London in July, and a great deal of interesting discussion was held on diseases of tropical plantation crops. It was convincingly shown that the diseases of many valuable plants are primarily due to soil conditions, and that fungi are parasitic only when these conditions make the hosts susceptible. Professor Blackman's address to the Botanical Section of the British Association also dealt with parasitic diseases in plants. He explained that the practice of medicine among plants is far more difficult than among animals. The plant seems to respond in the same way to totally different invaders, whereas, in animals, if certain symptoms appear, it is much more easy to assume the invasion of one particular parasite. Plants show natural immunity, but none of the acquired immunity produced in animals after one attack of a disease; probably this is related to the lack of a circulating blood-stream.

Important works on the production of field-crops and grassland farming have been published by Hutcheson and Wolfe and by Malden. They are written on severely practical lines and illustrate the increasing attempt by scientists to put their special knowledge at the disposal of the farmer.

The first Scottish Cattle-breeding Conference held at Edinburgh proved a great success, but it became evident that there is much need of scientifically trained journalists who can interpret to the breeder the work of men of science. Many of the breeders' problems are no longer problems to the geneticist; but the science of genetics is at present made difficult of access to the "practical man" by an extreme technicality of language.

In the Government Pavilion at Wembley there was an exhibit by the Cambridge School of Agriculture which deserves especial mention. It illustrated fertility and sterility in domestic animals, and in connection with it an admirable explanatory memorandum was issued.

Stocker, of Bremerhaven, has issued an interesting account of his experimental work with Montfort on moorland plants. He claims to have shown that the water of moorland soils is not toxic to plants like heaths, and that transpiration and water absorption go on freely. The theory of "physiological dryness," if this view be accepted, becomes untenable, so far as such plants are concerned. Wilson's work on Australian xerophytes shows that in these also there are no special powers of accommodation when they are exposed to rapid increases of temperature or to hot winds. He claims that the average transpiration rate per million stomata has no apparent relation to the depth to which the stomata are sunk, or to the amount of protection which hairs and other outgrowths might be supposed to afford.

Orr, of Edinburgh, has found in the mucilage of the leaf-glands of Dioscorea macroura quantities of a bacterium which he has isolated in pure culture and proved to have the power of nitrogen fixation. Lipmann and Taylor, working in America on water-cultures of wheat and barley, claim to have shown that green plants are capable of fixing atmospheric nitrogen without the intermediation of bacteria.

The development of very powerful electric gas-filled lamps equipped with reflectors has made it possible to work on a large scale on the effect of artificial light on the growth of plants. American experiments show that the bloom in most cases can be accelerated by about eight days. Flammarion reports from France that plants grown under red light are four times as large as those grown under white; red, orange, and yellow rays stimulate plant life; blue rays have an arresting effect; ultra-violet rays in the right proportion are beneficial, but when in excess they cause shrivelling of the leaves and death.

Increasing contamination of the air by London smoke has made it impossible to grow coniferous trees at Kew, and a new national pinetum has been started at Bedgebury in Kent, where experimental work can also be carried on.

A large aquarium was opened in April in the Zoological Society's Gardens at Regent's Park, London. There is a fresh-water hall with twenty-five tanks, a sea-water hall with twenty-five, and a tropical with forty tanks, most of which are small. A workroom, well equipped, is attached to the aquarium for zoological and economic research. Barret and Smith, in America, claim to have made successful cultures of an amoeba, Endamaba barreti, from the intestine of a turtle. medium employed was human blood serum one part, with nine parts of 0.5 per cent. salt solution. At the time of reporting, the work had been

The

carried on for nineteen months, and one strain was in its sixty-seventh sub-culture.

Another American worker, Cleveland, has confirmed by experiment the suggestion put forward by Grassi and Sandias some years ago that there is very close symbiotic connection between wood-eating termites and the trichonymphid protozoa living in their intestines. The termites furnish the flagellates with food and lodging, and the protozoa digest the fragments of wood and hand on some of the products to their insect hosts.

Woodruff and Moore cultivated the ciliate Spathidium spathula in standard beef-extract for 444 days; there was neither endomixis nor conjugation during this time, and the authors consider that this protozoon can reproduce by simple division indefinitely, given suitable environment.

A very interesting little crustacean, Thermosbæna mirabilis, is described by Monod from a Roman bath-cistern in Algeria. The creature lives in water coming from a hot spring with a temperature of 48° C. Allowing for peculiarities probably resulting from subterranean life, systematists consider that we have in Thermosbona the representative of a new order of crustacea linking the Mysidacea with the Tanaidacea.

So little is known about the physiology of invertebrates that Yonge's work, published this year, on the feeding and digestive processes of the Norway lobster is a very real contribution to biology.

Professor Teacher has published some interesting observations on the implantation of the ovum and the early development of the trophoblast in man.

The ovum has an entering or implantation pole and an adhering or closing pole, and this polarity determines the position of the embryonic rudiment in the blastocyst and the situation of the placenta.

Cannon has made a valuable addition to our knowledge of crustacean embryology by his work on the development of an estherid.

Pearl and Parker, in America, have studied the duration of life of Drosophila, the fruit-fly; they find that under conditions of feeding, the wild flies have an expectation of life three times as great as in the mutation with vestigial wings, whereas under starvation, the mean length of life is the same for both.

Investigations by Lloyd and his colleagues on tse-tse flies in northern Nigeria confirm the belief that Glossina morsitans and G. tachinoides breed almost solely in the dry season. There is some indication that postponement of grass-burning may interfere with free breeding of these tse-tses. This is to be tested, and an experiment is also to be made of excluding game and pig, by means of fencing, from one of the dry season haunts of the flies. Valuable information has been gathered as to their feeding habits.

In September the Cambridge and Royal Society Expedition set out to investigate the biology of the Suez Canal. The waters near the shores of the Bitter Lakes, which in 1882 Keller described as almost devoid of life, are now found to yield a rich and interesting fauna. The Expedition is studying organisms attached to ships, piles, and buoys in the Gulf of Suez, and has put out wooden floats which should eventually give valuable

information as to the factors helping in the distribution of such organisms and their growth.

The St. George Expedition reached the Isthmus of Panama in June, and very large zoological, botanical, and archæological collections are being made.

The Trustees of the British Museum have arranged to explore the deposits of deinosaur bones in Tanganyika Territory. The beds in which these occur date back to the early Cretaceous period, and before the war yielded the Germans some valuable deinosaur fossils. The work will occupy two years.

The Permian rocks have hitherto shown little evidence of insect life. Sellards and Dunbar announce this year that they have found thousands of very well-preserved specimens of may-flies, cockroaches, dragon-flies, etc., in the Lower Permian of St. Elmo, Kansas.

The first stalked crinoid of tertiary age ever described from the western hemisphere-a species of Balanocrinus-has been reported by Springer from the lower Miocene of Haiti.

X-ray photographs of mummies have been taken in America, and by their means it is possible to learn what has been buried with the body and whether it is advisable to proceed with unwrapping or not.

The value of the cinema as an instrument in education is more and more fully realised. The Field Museum of Natural History, Chicago, arranged this year a series of twelve free programmes of moving pictures with occasional lectures for children on Saturday mornings. The films shown dealt with aspects of botany, zoology, and geology, and printed museum stories" were given to the children at each entertainment, telling them more about the animals and plants they had seen and explaining how to find further information from appropriate cases in the

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museum.

Talks on biological subjects are becoming more frequent on the programmes of the British Broadcasting Company. In the right hands, the possibilities for popular education in science by means of wireless are

enormous.

The controversy between the Mechanists and the Vitalists dies down only to rise again with fresh vigour. Of recent years the vitalists have been somewhat in the ascendant. Interesting therefore is the opinion expressed by such an authority as Professor A. V. Hill in the Joule Memorial Lecture delivered at Manchester on "Thermodynamics in Physiology"-"There is no good evidence that the ordinary laws of physics and chemistry, including those of thermodynamics, do not apply to the living cell and animal. When proof to the contrary is alleged, it is always found to be of the kind which requires a high degree of credulity, an emotional preference for the miraculous, an imperfect appreciation of the canons of scientific thought, or an actual ignorance of the principles involved."

THE PHYSICAL SCIENCES.

The year has been chiefly notable for an unusual number of conferences and anniversaries. The most important of the former was the World Power Conference held at Wembley, June 30-July 12; while

among others held in London were the Fourth International Congress of Refrigeration and the Empire Mining and Metallurgical Congress. Conferences in other countries attended by British delegates included the International Mathematical Congress at Toronto, the International Union of Geodesy and Geophysics at Madrid, the International Commission on Illumination at Geneva and an International Conference on Soil Physics in Rome. The anniversaries in chronological order were (1) the jubilee of the formation of the Physical Society of London which was marked by a series of meetings on March 20-21, an exhibition of historic apparatus, and a banquet, attended by H.R.H. the Duke of York and the Prime Minister, on March 22; (2) the centenary of the birth of Lord Kelvin which was celebrated on June 26 and again in July in conjunction with the World Power Conference; (3) the centenary of the Franklin Institute, Philadelphia, in September, and (4) the jubilee of the Yorkshire College of Science, known for the last twenty-one years as the University of Leeds, in December.

The British Association, with Sir David Bruce as President, met in August at Toronto. The choice of meeting-place was, perhaps, rather unfortunate when so much of scientific interest was to be seen at the Empire Exhibition. Nevertheless, in spite of this counter-attraction the overseas party at Toronto numbered 573 out of a total enrolment of 2600 which included 300 members from the United States.

From the public view-point the developments in wireless telegraphy have again excited most interest. The success which had attended the attempts of the British Broadcasting Company to relay speech and music transmitted from America by waves of only 100 metres wave-length concentrated attention on the possibilities of short wave transmission. The results obtained in 1924 by Senatore G. Marconi (and indeed by amateur experimentalists also) have been of an even more notable character. Continuing experiments which he had commenced in 1916, Marconi carried out a series of investigations between Poldhu, in Cornwall and his yacht Elettra, using wave-lengths varying from 32 to 92 metres, and found that the daylight range of practical communication increases very rapidly as the wave-length diminishes. Thus when the power used at Poldhu was 12 kilowatts the 32 metre wave was regularly received all day at Beyruth, 2100 miles away, while at Madeira, 1100 miles distant, the 92 metre wave could not be detected for many of the daylight hours. Later in the year Poldhu was received for 23 hours out of the 24 at Sidney although the power used was only 15 kilowatts, and similar success has been obtained with the stations at Cape Town, Bombay, Rio, and Buenos Ayres. To appreciate precisely the nature of this achievement it is only necessary to remember that the new Empire Station which is being erected by the Post Office at Rugby is designed to employ 1000 kilowatts with a wave-length of from 12,000 to 16,000 metres. The use of short waves has made it economically possible to construct reflectors which tend to restrict the waves to one selected direction-the Beam Systemso that further economies in power consumption are possible while some degree of secrecy is obtained. Finally it may be noted that Marconi estimates that the practicable speed of signalling with short waves will prove to be as much as 100 times that with waves of the order of 10,000