428 



NA TURE 



[Sei'TEmber 3, 1903 



other farms ; (5) next to variety, season, and then soil, most 

 affect the composition of swedes; the influence of manurmg 

 is not marked. The fourth conclusion is warranted by the 

 facts which Mr. Collins brings forward, but this point is 

 one on which further information is wanted, for it seems 

 probable that the relative position of different varieties 

 might change if the varieties were exposed to markedly 

 different conditions. 



A Bulletin recently issued by the U.S. Department of 

 Agriculture, entitled " The Mango in Porto Rico," dis- 

 cusses the prospects of mango cultivation on the island. 

 Porto Rico grows mangoes in abundance; the climate is 

 very favourable, and the trees are free from disease, but 

 hitherto seedling trees only have been grown, and one is 

 not surprised to read that the mangoes have met with but 

 little favour in the American markets. The fame of the 

 Bombay mango is due to the fruit of grafted trees, and it 

 is rarely that trees raised from seed produce fruit worth 

 eating. Seedling trees abound in every village, but first- 

 rate trees are very uncommon. The short list given in 

 Woodrow's " Gardening for India " shows how rare really 

 good seedlings are. When the Americans import fine 

 strains and take to growing grafted mango trees the in- 

 dustry is certain to make rapid progress. We gather from 

 the Bulletin that this subject is likely to engage the atten- 

 tion of the local experiment station. We hope it may, for 

 if the matter is taken up with the energy characteristic of 

 the American stations, there is every prospect of a great 

 increase in the supply of the finest of tropical fruits. 



REPORT OF THE MALARIA EXPEDITION 

 TO THE GAMBIA. 



THE Liverpool School of Tropical Medicine has just 

 issued a most important and practical report upon the 

 prevention of malaria in the tropics.' Dr. Dutton, who 

 conducted the expedition with conspicuous success, shows 

 with striking clearness how a great deal of disease is due 

 to the want of knowledge of the nature of malaria, and 

 that during the dry season the residents are largely to 

 blame for the appearance of the disease. It is one of the 

 most hopeful reports ever issued by the school, and it shows 

 that the governors and others in authority upon the coast 

 are fully alive to the importance of stamping out malarial 

 diseases. The report is an immense step forward in pre- 

 ventive medicine. 



The object of the expedition was to investigate the con- 

 ditions under which mosquitoes were propagated in the town 

 of Bathurst and at the principal stations of the colony, and 

 to suggest methods of destroying these insects. Malaria 

 was found to be prevalent in the colony ; 80 per cent, of 

 the native children examined harboured malaria parasites in 

 their blood. The liability to infection of the Europeans com- 

 mences soon after the rains are established, lasting up to the 

 end of November. The various breeding places of mosquitoes 

 are described in detail in chapter iv. of the report, particular 

 mention being made of the wells, canoes, boats, lighters, 

 cutters on the foreshore, and of the grass-clogged trenches 

 in many of the streets, which together supply Bathurst 

 with the majority of its mosquitoes during the wet season 

 and for part of the dry season. The number of mosquito 

 breeding places present in compounds was found to vary 

 with the social position of the occupier. They increased 

 in extent and number in proportion to the wealth and posi- 

 tion of the occupier. 



An account of the examination of one of the large com- 

 pounds illustrates to what extent mosquitoes are bred by 

 the white man in the tropics on his own premises. 



In one factory yard were found six barrels, and in the 

 garden there were seventeen tubs and eight small wells, all 

 breeding quantities of Culex, Stegomyia, and Anopheles 

 mosquitoes. Besides these dry season breeding places, dis- 

 carded domestic utensils were scattered about the yard and 

 garden which, in the wet season, would have acted as 

 breeding plates. It is pointed out that during the dry 

 season, from November to May, natural breeding places for 



i " Report of the Malaria Kxpeiition to the Gambia. 7902, of the I iver- 

 pool School of Tropical Medicine and Medical Parasitology." By J. E. 

 Button, M.B , and an appendix by F. V. Theobald, M.A. Pp. 46+xi! 

 (Liverpool: University Press, 1903.) 



NO. 1766, VOL. 68] 



mosquitoes in Bathurst cease to exist, and from this period 

 the people breed mosquitoes solely in their own compounds. 



In chapter v., which deals with the prevention of malaria 

 in Bathurst, a campaign against the mosquito is advocated ; 

 the town is judged especially suitable for its success. Thus 

 Bathurst is situated on a practically isolated piece of land 

 surrounded on nearly all sides by a broad expanse of sea 

 water. The amount of land to be dealt with is compara- 

 tively small, viz. about a square mile. The surface is fairly 

 level, sandy, absorbing water readily. In this area the 

 breeding places of mosquitoes are a known quantity, the 

 artificial, or those made by man, being in excess of the 

 natural. The rainfall is very small, and rain occurs only 

 during four out of the twelve months of the year. 



The probability of the introduction into Bathurst of 

 yellow fever from Senegal is pointed out as another reason 

 for attacking the mosquito. The expedition was informed 

 by His Excellency the acting Governor, H. M. Brandford 

 Griffith, of the intention on the part of the Colonial Govern- 

 ment to enter upon a crusade against the mosquito, and 

 on November 18 the preliminary removal of rubbish from 

 houses and compounds began ; a sanitary inspector was 

 appointed, and received special instruction in the work. 

 Under him worked a gang of labourers, and at the time of 

 the departure of the expedition (January 10) 363 houses and 

 compounds had been inspected. From these 131 cartloads 

 of old tin pots and other rubbish were removed. On the re- 

 turn of His Excellency the Governor, Sir George C. Denton, 

 the inspector and a sufficient staff of labourers were 

 appointed permanently, and a grant of 200J. per annum 

 was given for the special anti-mosquito work. Anti- 

 mosquito regulations have been drawn up by the Colonial 

 Government. These are given at the end of the report. 



An apoendix, bv Mr. F. V. Theobald, is attached to the 

 report ; in it are described the various species of mosquitoes 

 collected by the expedition, many of which were new to 

 science. 



ZONES IN THE CHALK. 

 TN Nature for August 8, 1901, attention was directed to 

 ■^ the second part of Dr. A. W. Rowe's researches on 

 the zones of the White Chalk. We have now had the satis- 

 faction of receiving the third part of this most interesting 

 and important work, which deals with the Chalk of Devon 

 {Proc. Geol. Assoc, vol. .xviii. part i., 1903). 



Working the palaeontology with such aids as can be 

 gathered from the local stratigraphy and lithology, the 

 author, assisted as before by Mr. C. D. Sherborn, has 

 added extensively to our knowledge of the successive forms 

 of life that are met with in the Chalk between Sidmouth 

 and Lyme Regist Whether or not the limits of the 

 zones happen to coincide with definite stratigraphical 

 limits, these latter afford useful data, and one marl band 

 to which the author directs special attention, forms the 

 plane of division between the zones of Terebratulina gracilis 

 and Holaster planus. Such definite and continuous bands 

 of rock (so far as they can be traced) must afford 

 even more precise evidence of contemporaneity than 

 the presence of this or that fossil. Even a tabular flint- 

 band has proved " an .almost constant feature throughout 

 th'' coast " — an interesting fact, and one that was not to 

 be expected. It is admitted that the name-fossils are not 

 always confined to their zones. Holaster planus is found 

 by Dr. Rowe throughout the zone of Terebratulina gracilis. 

 But the guide-fossils, the general assemblages associated 

 with the name-fossils, while they exhibit here, as else- 

 where, local variations, tell the same story of the successive 

 zones or stages of life, and indicate their approximate limits. 

 Perhaps too much importance is given to the effort to fix 

 a precise divisional plane between zones. When such 

 divisions depend on the forms of life, and the succession 

 of life is continuous though gradually varying, there can 

 be no absolute planes of division, except through the 

 absence or erosion of strata belonging to a particular period 

 of time. 



The work before us is rich in its stores of interesting 

 facts. The zone of Rhynchonella Cuvieri presents noteworthy 

 features in the presence of Micraster cor-bovis and M. 

 h'skei, the zone of Terebratulina gracilis^ is " singularly 

 rich in fossils," while in the zones of Holaster planus and 



