756 



NATURE 



[August 12, 1920 



uniovulate, the latter type having a single chorion, 

 and it is found that about i per cent, of all human 

 births are plural births. But in the relatives of 

 mothers who have repeated twins tfeis proportion 

 rises to 4-5 per cent., indicating the inheritance of 

 twinning in the strain. Twinning is, however, almost 

 equallv frequent (4-2 per cent.) in the near relatives 

 of the fathers of twins. The tendency to repetition 

 of identical twins is even higher than when both 

 types are considered together. Double ovulation is 

 far commoner (frequency 5-10 per cent.) than twin 

 births, and here the male factor comes in, for it has 

 now to be recognised that human germ-cells fre- 

 quently contai*! lethal factors which arrest develop- 

 ment at an early stage, or may even prevent more 

 than one egg being fertilised. In relation to this is 

 the fact that highly fecund families more frequently 

 have twins. Human beings thus possess the biovulate 

 type of twinning found in carnivora, herbivora, and 

 r'odentia, and also the uniovulate type found in the 

 armadillo, which regularly produces four young of 

 the same sex at a birth by budding from the young 

 embryo. 



That the Philippine hawksbill turtle {Eremochelys 

 imbricata) is in dire need of stringent protection is 

 evident from the account of this species given in the 

 Philippine Journal of Science (vol. xvi.. No. 2) by Mr. 

 * E. H. Taylor, of the Bureau of Science, Manila. 

 Practically all the Philippine tortoiseshell is brought 

 into the market by the native fishermen, who are so 

 eager to secure their prizes that they wait for 

 days for the arrival of the female to lay her eggs 

 on the beach. Often she is speared before a single 

 egg is laid. Should they have patience enough to 

 allow her to fill the "nest" the end is the same, for 

 every egg is eaten. Obviously it will not be long 

 before this source of revenue is lost for ever. 



The August number of Conquesi, a magazine 

 devoted to the popularisation of science, is a model 

 of what such magazines should be, for not only are 

 its contents designed to appeal to a wide circle of 

 readers, but also every article is lucidly written and 

 well illustrated. Taking subjects at random — for it 

 would be difficult to make a deliberate choice — one 

 may mention the essay by Mr. R. I. Pocock on the 

 common animals of the sea-shore, that on wild white 

 clover by Mr, J. J. Ward, and the article on the 

 Davon micro-telescope by Mr. F. Talbot. Besides 

 these are not less fascinating talks on the ships of the 

 future bv Mr. W. Horsnaill, on seaside meteorology 

 by Mr. Joseph Elgie, and on the sands of the sea- 

 shore by Mr. C. Carus Wilson. 



The attention of those who are interested in the 

 campaign against rats may be directed to the second 

 edition of Mr. M. A. C. Hinton's pamphlet (67 pp., 

 2 plates and 6 text-figures) which has been recently 

 issued by the British Museum (Natural History). 

 This work contains an excellent summary of the 

 characters, habits, and economic importance of rats, 

 and of the relation of rats to the spread of disease in 

 man and animals. In this edition additional details 

 are given on the rate of increase of rats, and refer- 

 NO. 2650, VOL. 105] 



ence is made to the occurrence in the rat of Spiro- 

 chaeta icterohaeinorrhagiae, the organism of spiro- 

 chaetal jaundice (Weil's disease) in man. After 

 emphasising the urgent need for action against the 

 large rat population of Great Britain, Mr. Hinton 

 gives a concise account of the chief repressive 

 measures. Barium carbonate is recommended as the 

 safest poison, mixed in the proportion of one part 

 with eight parts of oatmeal, and made up with a 

 little v/ater into a stiff dough. Among other methods 

 to which attention is directed are trapping, which 

 should be continuous and systematic, and placing in 

 the run-ways of the rats birdlime trays with an attrac- 

 tive bait in the centre — a method which has given 

 good results in Liverpool, London, and elsewhere. 



Italian biologists are to be congratulated on their 

 enterprise in founding, in difficult circumstances, a 

 new biological publication, Revista di Biologia, which 

 is published bimonthly in Rome, and is edited by 

 Profs. Gustavo Brunelli and Osvaldo Polimanti. 

 The review is to be devoted largely to the considera- 

 tion of problems of general biological interest, but its 

 pages are also open to record the results of researches 

 in special subjects. Six fascicles, forming the first 

 volume of 744 pages, have recently reached us. Prof. 

 Brunelli contributes to the first fascicle a vigorous 

 article on the place which science, and especially 

 biology, should occupy in the national life of Italy. 

 He points out that the future of Italy is essentially 

 bound up with agriculture and problems of the land, 

 and that in the economic development of the nation 

 biology must therefore take a leading art. He pleads 

 also for more attention to hydrobiology, and for a 

 closer co-operation between medical practitioners and 

 biologists — for instance, in anti-malarial measures 

 and in social hygiene generally. Among the special 

 articles two may be briefly referred to : the first 

 by Prof. Pierantoni on physiological symbiosis, with 

 special reference to the part plaved by symbiotic 

 organisms in light-production in luminous organs, and 

 the second by Prof. Enriques on the results of experi- 

 ments in breeding blow-flies {Calliphora erythro- 

 cephala), in which he shows that while some of the 

 pairings give rise to a high proportion of living 

 offspring, other pairings produce larvae about one- 

 fourth of which, although kept under optimum condi- 

 tions, cease to feed after two or three days and die. 

 Prof. Enriques does not consider that the explanation 

 of Morgan, in his important work on lethal factors 

 in Drosophila, holds for Calliphora. The Revista 

 will not only fulfil its object in stimulating and en- 

 couraging biological research in Italy, but will also 

 afford workers in other countries a ready means of 

 keeping in touch with the chief lines of research of 

 Italian biologists, and we cordially wish it success. 



Dr. R. Ruggles Gates has given (Proc. Rov. Soc. 

 London, B, vol. xci., 1920, pp. 216-23) a preliminary 

 account of the meiotic phenomena in the pollen 

 mother-cells and tapetum of lettuce, in which several 

 matters of genera! bearing on cytological conceptions 

 and on problems of genetics are considered. The 

 chromatin of the nuclei of the tapetal cells, particu- 

 larly of the binucleate cells, exhibits the synaptic knot 



