August io, 1916] 



NATURE 



479 



and mangrove swamps seem to be little different 

 from others in the same region. No fresh light 

 is thrown on their origin. They differ mamly 

 from Indo-Paciiic reefs m the shallowness of the 

 lagoons — seldom more than ten fathoms — within 

 the barrier reefs, but, unfortunately, in an other- 

 wise well-got-up book, the chart given is totally 

 inadequate. 



Some of the party were more interested in the 

 land than in the sea, and much of their time was 

 spent in hunting for land-shells. It is upon the 

 great limestone ridges (sierras) which stretch 

 through Cuba from east to west that that island's 

 astounding wealth of land moUusca is found. In 

 addition, there are isolated mounds of limestone 

 ^mogotes), rich in peculiar genera and species. The 

 author is an authority on these, and we are sorry 

 not to hear much more of them. Clearly he con- 

 siders that the land moUusca reached their climax 

 after the elevation of the limestones, apart from 

 which they cannot maintain themselves. Later, 

 abrasion has been at work, and their original range 

 has dwindled as continuous limestone areas were 

 replaced by broken sierras and isolated mogotes. 

 Isolation in plastic genera gave rise to the forma- 

 tion of new species. The widely distributed 

 families, genera, and species are hence the ancient 

 forms, the isolated genera and species their 

 modern descendants. 



The Statesman's Year-Book. Statistical and His- 

 torical Annual of the States of the World for the 

 year 1916. Edited by Dr. J. Scott Keltic, 

 assisted by Dr. M. Epstein. Pp. xliv+i56o + 

 maps 4. (London : Macmillan and Co., Ltd.) 

 Price I05. 6d. net. 

 The "Statesman's Year-Book" makes its ever- 

 welcome appearance. The editors. Dr. Scott 

 Keltic and Dr. Epstein, have been able to obtain 

 much statistical information regarding the belli- 

 gerent countries, and, in- the case of Germany, to 

 include facts and figures based upon the latest offi- 

 cially published information. Maps show the rail- 

 way schemes in Asiatic Turkey and in Africa 

 respectively, and the distribution of Germans both 

 in the world as a whole and, in greater detail, in 

 :he United States. The introductory tables pro- 

 vide a world review of the production of wheat, 

 sugar, ships, etc., and usually include the year 

 -inder review. There is an illuminating summary 

 vhich deals with the Great War in regard to 

 jopulation, books, loans, and war finance. The 

 iVllies outnumber the Central Empire Alliance by 

 j> to I ; the war has cost already more than 

 1 10,000,000. oooL, of which a quarter has been 

 -pent by Britain, nearly a quarter by Germany, 

 md a fifth by Russia. Mr. John Leyland has 

 evised the information concerning the navies of 

 I he world in succession to the late Mr. Fred T. 

 ane. We cull a few facts at random : There is a 

 olunteer corps among the 2328 males in the 

 <land Islands; Oregon University, organised 

 1876, has 108 professors; the Free City of 

 >rtmen in 191 3 exported goods valued at 

 o.iio.oooZ. to Great Britain, about 9 per cent. 

 t the total exports of the port. 



XO. 2441, VOL. 97] 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the 'juriters oj, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



is Proto-Oxygen the Principal Constituent of the 

 .A toms ? 



.As from Moseley's experiments we know the num- 

 ber of rare-earth elements between La and Ta to be 

 15, the mean difference between atomic weights is, 

 from Mg on, for 6 atomic numbers, 16 exactly. 

 So for Mg (Atw. 24, N 12) and Th (.\tw. 232, N 90) 

 we get (232 — 24)/i6 = (90— I2)/6=I3. Between U 

 and Nt this difference of 238 — 222 = 16 is known 

 to be a difference of 40+ 2^ particles. But 

 if the a particle is the real constituent of the atoms, 

 40+2^ is the inner part of the oxygen atom (the 

 additional 6 /3 particles being electrons of valency). 

 That atomic weights are not twice the atomic num- 

 bers would be due thus to the formation of 04^; = ^ 

 particles, or proto-cxygen, within the nucleus, and 

 radio-activity should be the disintegration of these 

 6 particles into their constituents. It may be remarked 

 that aiP2 = 6 is similar to H + fii = a (which might be the 

 formula for the o particle). A. van den Broek. 



Gorsel, Holland, July 17. 



International Commission on Zoological Nomenclature. 



Opinions on the following subjects are before the 

 International Commission on Zoological Nomen- 

 clature for final vote : — 



Opinion 70.^ — The case of Libellula americana, L., 

 1758, vs. Libellula americanum, Drury, 1773. 



Opinion 71. — Interpretation of the expression 

 "typical species" in Westwood's (1840) synopsis. 



Opinion 72. — Herrera's zoological formulae. 



Opinion 73. — Five generic names in Crinoidea, 

 ninety-two generic names in Crustacea, and eight 

 generic names in Acarina, placed in the official list 

 of generic names. 



If anyone is interested in these opinions and has not 

 alreadv been reached bv the Commission, and there- 

 fore has not had an opportunity of being heard upon 

 them, he is cordially invited to send his views to the 

 Secretary' of the Commission, and if any new point is 

 raised that is likely to alter the opinion of the Com- 

 mission, the data will be forwarded to the Commis- 

 sioners for consideration. 



C. W. Stiles, 

 Secretary to the Commission. 



Office of Secretary to International Commission 

 on Zoological Nomenclature, 

 Smithsonian Institution, Washington. D.C., 

 July 13. 



The Magnitude of 6 Eridani. 



The arguments of Mr. E. J. Webb (Nature, vol. 

 xcvii., p. 341) seem conclusive as to this star having 

 been of the first magnitude at the epoch of Ptolemy's 

 catalogue, but are perhaps less conclusive as to its 

 magnitude at any other time, though the reviewer of 

 Peters's and Knobel's work is surely wrong in assum- 

 ing that" .-M Sufi would find any difficulty in judging 

 between a first and a third magnitude star at an 

 altitude of 10°. Have astronomers considered the 

 possibilitv of Eridani having been practically a tem- 

 porary- star at Ptolemy's epoch? Do Peters and 

 Knobel come to any conclusion as to the magnitude 

 of thi^ star? T. W. Backhouse. 



West Hendon House, Sunderland, .August 4. 



