88 



NATURE 



[September i6, 1920 



the Guaharibos rapids. The traverse is checked by 

 more than forty astronomical stations, where time was 

 obtained by field wireless from Darien and Washing- 

 ton. Magnetic observations were taken at more than 

 twenty of the stations. Meteorological readings were 

 taken four times daily in conjunction with similar 

 readings at the same hours at Para. Much attention 

 was paid to geological research. Finally, Dr. Rice 

 says that the survey of the diseases encountered will 

 form one of the not least valuable results of the 

 expedition. 



The problem of suitable maps for aviators con- 

 tinues to attract much attention and is (ar from 

 being satisfactorily solved. In the Geographical 

 Journal for Augfust (vol. Ivi., No. 2) Capt. H. A. 

 Lloyd has a short paper, illustrated by many admir- 

 able photographs, on the classification of the ground 

 from the air. Experience on the Western front during 

 the war convinced Capt. Lloyd that the whole area 

 could be divided into distinctive zones differentiated 

 by the shapes of fields or by the industries carried on 

 in particular localities. A recognition of these types 

 of terrain was found to enable a pilot to determine 

 his approximate position. This was particularly 

 valuable in the case of a pilot losing his wav owing 

 to clouds or in flight over the country for the first 

 time. Thirteen types of ground were recognised and 

 taught to pilots in the area of the Western front 

 between the sea and the River Oise. Under war 

 conditions this classification had its limitations 

 because the destructive effect of battle, as a rule, 

 removed all features visible to the eye and generally 

 to the camera. It is also noted that, under normal 

 conditions, while the shape of the fields and other 

 features remain constant, the height of the vegeta- 

 tion affects the appearance of the photograph. Thus 

 a field of ripe corn may look almost as dark as a 

 row of trees. These seasonal variations would need 

 to be taken into account in making use of such a 

 classification in map-construction. Capt. Lloyd 

 also discusses the classification of landmarks, and 

 insists that small-scale maps, such as are used in 

 flying, should portray the chief features of towns so 

 , that a glimpse of a town would be enough for an 

 aviator to locate his position. These considerations 

 entail the omission of much of the detail shown on 

 maps for land use, so that the features conspicuous 

 from the air may stand out boldlv. 



A PROSTRATE variety of potato has been found in 

 the breeding experiments of Messrs. R. N. Salaman 

 and I. W. Lesley {Journal of Genetics, vol. x.. No. i), 

 which, it is suggested, may be useful for potato- 

 growers in semi-arid climates, since the foliage, lying 

 on the ground, has a considerable effect in conserving 

 the soil moisture. This variety breeds true, and is 

 shown to differ from the upright type in a failure to 

 form secondary xylem in the stem. A procumbent 

 variety, the stems of which turn up at the end, has 

 also appeared. Anatomically, it agrees with the pros- 

 trate variety. In both these types the crop of tubers 

 is unaffected. 



NO. 2655, VOL. 106] 



In an interesting further study of melanism in 

 moths, Mr. J. W. H. Harrison (Journal of Genetics. 

 vol. X., No. i) discusses crossing experiments with 

 Tephrosia bistortata, T. crepusciilaria, and their 

 melanic varieties. The melanic variety of T. crepuscu. 

 laria behaves as a simple Mendelian dominant to the 

 type, and the same has been shown to be true of 

 various other melanic varieties. But in crosses of 

 T. bistortata with the melanic form of the other 

 species a great range of colour forms was obtained in 

 Fj and Fj, with no indication of Mendelian segrega- 

 tion. The results are interpreted as showing that the 

 unit factor for melanism has been modified, and in 

 some cases broken up so that it has practically dis- 

 appeared. 



As a first study of inheritance of egg-weight in 

 fowls, Philip Hadley and Dorothy Caldwell (Bull. 181, 

 Rhode Island .^gr. Expt. Station) make an analysis 

 of the normal distribution of egg-weight in White 

 Plymouth Rocks. Egg records from a flock of thirty- 

 nine hens through eight years showed that individual 

 hens differed markedly in the weight of eggs laid in 

 any period. The first eggs of any year are smaller, 

 increasing to a maximum in April, then falling to a 

 minimum in July or .August, followed by another 

 maximum and minimum in September and November 

 respectively. After the second laying year these 

 maxima appear less clearly, and after the fourth there 

 is a progressive decrease in the weight of eggs pro- 

 duced each year. There apjjears to be a slight ten- 

 dency for heavier hens to lay larger eggs. 



The attention of workers on Diptera is directed to 

 Mr. E. Brunetti's catalogue of Oriental and South 

 Asiatic Nemocera, which has been published as 

 vol. xvii. (300 pp., June, 1920) of the Records of the 

 Indian Museum. Mr. Brunetti states that he has 

 included in his catalogue all the names of species 

 available up to the middle of 1919. In nomenclature 

 his policy has been to retain the names employed by 

 the principal dipterologists of the last century ; he 

 believes in "continuity before priority," and does not 

 agree with the general overturning of generic and 

 specific names, suggested by strict priorists, which 

 arises out of the much discussed "1800 paper" of 

 Meigen. For each species the author gives the 

 essential bibliographical references and synonyms, and 

 indicates the distribution. The location of the type- 

 specimen, where this is known, is stated. The Culi- 

 cidae (mosquitoes) receive careful consideration, and 

 the list of these extends over ninety-six pages of the 

 catalogue. 



In view of the present scarcity in the supply of 

 cotton, the attempts now being made to establish 

 cotton-growing on a large scale in Mesopotamia are 

 of particular interest. Cotton has been grown in 

 Mesopotamia from very ancient times, and is still 

 cultivated in small quantities by the Arabs in con- 

 junction with food-crops along the banks of both the 

 Tigris and Euphrates. The fibre is used locally for 

 spinning and as a stuffing material for pillows and 

 mattresses. The country possesses a soil and climate 



