NA TURE 



[June 



1 90 1 



into air have been determined. The following examples have 

 been taken from Landolt and Bernstein's tables :— 



Gas or Vapour. 

 Water vapour 

 Carbonic acid gas 

 Alcohol 

 Ether 



Coefficient of Molecul: 



Diffusion into Air. Weight. 



.. o-iqS ... 18 



0'142 ... 44 



O'lOI ... 46 



0-077 ... 74 



In the above we .'^ee that the coefficients of diffusion follow 

 the inverse order of the molecular weights. In cases of the 

 simpler gases it has been shown experimentally that the coeffi- 

 cient of inter-diffusion is approximately inversely proportional 

 to the square roots of the product of the molecular weights. If 

 we apply these considerations to the emanations we see that it 

 is a gas or a vapour of molecular weight (allowing a wide 

 margin) probably lying between 40 and 100. These numbers 

 exclude the possibility of the substance being a vapour of 

 radium, for it has already been shown by M. and Mme. Curie 

 that the atomic weight of radium is greater than that of barium. 



We must, therefore, conclude that the emanation is in reality 

 a heavy radio-active vapour or gas. 



On account of the rapid decay of the radiating power of 

 thorium emanations it is not possible to determine its coefficients 

 of diffusion in the same way ; but special experiments show 

 that it diffuses rapidly, and is also probably gaseous in character. 

 The physical properties of these emanations or gases are most 

 remarkable. The radium emanation not only continues for long 

 intervals to be a source of radiation which is apparently similar 

 in character to easily absorbed Rbntgen rays, but in some way 

 manufactures from itself a positively charged substance, which 

 travels to the negative electrode and becomes a source of 

 secondary radio-activity. 



Space is too short to enter into the interesting question of the 

 possible explanation of these complicated phenomena. 



McGill University, Montreal, May 30. E. RuTHEKtORr). 



Long-tailed Japanese Fowls. 



A LITTLE while ago in your columns Prof Lankester referred 

 to this breed as " a magnificent sport,'' and considered the 

 occurrence of genius in mankind as a case of the same kind. In 

 Newton's " Dictionary of Birds," article " Feather," it is stated 

 that in these Japanese poultry the moult is checked or prevented 

 by some means unknown to Europeans. It is obvious that the 

 latter statement, if correct, is not compatible with Prof. 

 Lankester's description. If the breed really arose as "a mag- 

 nificent sport," I presume that the excessive growth of the tail 

 coverts would be due to a spontaneous variation, and not to some 

 artificial method of preventing the annual moult. After a great 

 deal of trouble I have succeeded in obtaining evidence, which 

 seems to ine unimpeachable, concerning the means taken by the 

 Japanese to produce this extraordinary elongation of feather in 

 the cocks of the breed in question. 



I will quote the words of my informant. He writes : — " With 

 regard to the treatment of these birds, in order to ensure very 

 great length of tail, they ought after they are six months old to 

 be kept on a perch as much as possible, and the tail feathers 

 should be pulled gently every morning, grasping the centre bone- 

 like part firmly with the finger and thumb, and, pressing steadily, 

 draw downwards towards the tip, each feather being done several 

 times; this softens the quill and causes it to lengthen. They do 

 not moult the feathers, but if one or more come out others 

 immediately grow in their place. The Japs themselves, those 

 who take great pride in their birds, always roll the long feathers 

 up, like a lady rolls up her hair, and tie them, whenever they are 

 let off their perches to walk about, which is about twice a day 

 for an hour at a time. . . . 



" I have often seen them thus treated in Japan, and the man 

 who brought mine over treated them in this way on the voyage 

 over, and I sent them (to purchasers) in their regular perch 

 cages." 



I think this, being the evidence of direct observation, is 

 enough to prove that the length of feather in these birds is not 

 correctly described as a "sport," but has been produced by 

 special artificial treatment. The effect of the treatment is 

 doubtless to irritate the papilla from which the feather grows, 

 and so cause increased growth, rather than to soften and 

 lengthen the already formed quill. The feathers appear to grow 

 throughout the year, so that when the moulting season is 

 reached they are not shed, but continue growing. 



NO. 1650, VOL. 64] 



There is no doubt that the peculiarity is to a certain extent 

 hereditary, but extreme length of feather cannot, I believe, be 

 produced without the special treatment. These fowls have been 

 bred in England, and I have seen specimens which had tail 

 coverts (and also hackles) longer than those of any European 

 breed, but so far as I know no specimens bred in Europe have 

 produced the extraordinary length of feather that is known to 

 occur in Japanese specimens, for example in the two stuffed 

 specimens in the hall of the Natural History Museum. It seems 

 to me reasonable to conclude that the hereditary effect is due to 

 the artificial irritation applied to a long succession of generations. 



Penzance, June 5. J. T. Cunningham. 



Variation in a Bee. 



0.\ September 24, soine years ago, I collected at Mesilla, 

 New Mexico, four examples of a wild bee of the genus Epeolus, 

 the species being probably identical with Epeolus bardns of 

 Cresson. In every one of these specimens the second transverso- 

 cubital nervure is incomplete, its lower half being wanting, on 

 one or both sides. In one example only is the nervure incom- 

 plete on both sides : in the other three it is incomplete on the 

 right side only. Such aberrations are not very uncommon 

 among bees, but they usually occur in single examples, and this 

 is the best instance known to me of their being inherited by a 

 number of individuals. What is here clearly a sport seems in a 

 fair way to become a racial character, and we seem to have a 

 good example of Bateson's "discontinuous variation." In the 

 genus Halictus certain species have only two submarginal cells, 

 instead of the usual three, and the same is true of Andrena. 

 These peculiar species are related to different groups of the 

 genera to which they belong, so that if it is proposed to regard 

 them as pertaining to distinct subgenera (or genera) by reason 

 of their venation, it becomes necessary to propose several sub- 

 generic names instead of one, because of the independent 

 evolution of the species. That this evolution has resulted from 

 the perpetuation of sports such as that described above we can 

 hardly doubt, but we are not thereby compelled to admit that it 

 may not also be beneficial to the species. 



T. D. A. COCKERELI.. 



East Las Vegas, New Mexico, U.S.A., May 2?. 



Foreign Oysters Acquiring Characters of Natives. 



The facts contained in Mr. Tabor's letter, however in- 

 teresting, supply no evidence for or against Lamarckism. 

 When at Whitstable, the individual French oyster has certain 

 characters impressed upon it by its environment. The next 

 generation, when compared with the natives, show certain 

 peculiarities, such as greater thickness of shell and greater 

 growing power. But this also we are able to interpret as the 

 reponse of the individual to the environment. If the pecu- 

 liarities appear in many successive generations, the same ex- 

 planation will account for the facts. If, however, Lamarckians 

 could show that the effect of the environment, as the generations 

 succeed one another, is cumulative, that the characters in ques- 

 tion become progrissively accentuated, then they would prove 

 their case. But it does not appear that they have any such 

 evidence at their command. F. W. Headlev. 



Haileybury College, Hertford. 



ITALIAN EXPLORATION IN ARCTIC 

 REGIONS. 

 'X'HE recent success of the Duke of the Abruzzi's 

 ■I- expedition, which carried the Italian flag nearer the 

 North Pole than ever flag flew before, has doubtless pre- 

 pared a public in Italy for the literature of Polar explora- 

 tion. The firm of Hoepli, who have conferred many 

 favours on Italian-speaking geographers, have just pub- 

 lished a history of Polar exploration in the nineteenth 

 century by Signer Hugues.' The book makes no clain> 

 to originality, being merely a condensed popular descrip- 

 tion of the Polar voyages of the late century, and although 

 more detailed on account of the shorter range of time 

 dealt with, and coming down to the year 1900, it cannot 

 compare with General Greely's compact handbook as a 

 work of reference for the student. The most serious 

 drawback is the want of a bibliography or a uniform 



1 "Lulgi Hugues-Le Esplorazioni Polarl nel Secolo XIX." Pp. xx -I- 

 374. Maps and Illustrations. (Milano : Ulrici Hoepli, iqoi). Price 12 lire. 



