April 6, 1905] 



NATURE 



545 



the interposition of a blackened brass disc slightly larger 

 than the solar disc. 



The resulting negatives showed distinct halos around 

 the disc, and, notwithstanding the fact that some time 

 elapsed between the successive exposures, these halos ex- 

 hibited the same form, thus testifying to their solar 

 origin. Some of the negatives were photographically 

 intensified by repeated copying, and reproductions of them 

 were submitted to the academy. In presenting the com- 

 munication M. Janssen — to whom M. Hansky acknow- 

 ledges his obligations for assistance and advice — stated 

 that " the photographs actually show the solar corona 

 with an intensity and a perfection only known on the 

 photographs obtained during total eclipses " {Coinplcs 

 rcndus, No. 12). 



Search-ephemeris for Tempel's First Periodic Comet 

 (1867 II). — Although Tempel's first comet has not been 

 seen during its last three perihelion passages, i.e. since 

 1879, M. A. Gautier, of the Geneva Observatory, thinks 

 that the probability of its re-discovery this year is great 

 enough to justify a careful search. For this reason he 

 re-publishes, in No. 4008 of the Astroiwmische Nach- 

 richten, the elements he prepared for the 189S apparition, 

 reduced to the mean equinox of 1905 o. .As the probable 

 time of perihelion is somewhat uncertain, he gives three 

 ephemerides, extending from March 31 to July 13, in 

 which this time is reckoned as May 25, .April 205, and 

 April 8-s respectively, the mean date being the most prob- 

 able. The declination varies from —16° to —31°, so that 

 the more southerly observatories are more likely to be 

 successful in the research. 



Right Ascensions of 2120 Southern Stars. — In an 

 appendix to " Observations made at the Hong Kong 

 Observatory during 1903," Prof. W. Doberck, the director, 

 publishes the right ascensions of 2120 southern stars for 

 the epoch 1900, as determined from observations made by 

 Mr. J. I. Plummer and himself during the years 1898 to 



'904- . , c.. 



The observations were made with a 3-mch Simms semi- 

 portable transit instrument, which, together with the 

 method of reduction and the comparisons with other cata- 

 logues, is briefly discussed in the director's preface. 



In the catalogue itself, the number of the star as given 

 in Lacaille, or Stone, or both, the R.-A., epoch and magni- 

 tude, the variation of the R.A. from .Stone's correspond- 

 ing value, the proper motion, and several other particulars 

 are given for each star. 



The Iris Diaphragm in Astronomy. — In a communi- 

 cation to the French Academy of Sciences, .M. Salet states 

 that he has recently and usefully adapted the iris 

 diaphragm to a telescope in which the magnification em- 

 ployed is 500. The diaphragm is placed very near to the 

 plane of the micrometer wires in front of the field lens, 

 and its ration d'etre is to prevent the light from the sky, 

 and from the illumination of the wires, from reaching the 

 eye when feeble objects are being observed, the diaphragm 

 being closed by an external cylinder when the object has 

 been brought to the centre of the field. By reducing the 

 extent of the micrometer wires, the diaphragm also re- 

 duces, or eliminates, the effect of astigmatism when 

 observations of double stars are being made (Comptes 

 rendiis, No. 9). 



Constancy of " Spark " Wave-lengths. — A question 

 which is of first importance to those observers engaged in 

 stellar line-of-sight work, viz. that of the constancy of 

 wave-lengths in spark spectra taken under various con- 

 ditions of discharge, has recently been re-investigated by 

 Mr. G. W. Middlekauff at the Johns Hopkins University. 

 A detailed description of the apparatus and methods em- 

 ployed, together with the results obtained, appear in No. 2, 

 vol. xxi., of the Asirophystcal Journal. 



Mr. Middlekauff used a concave Rowland grating of 

 20,000 lines to the inch and a focal length of 21-5 feet. 

 The self-induction in the spark circuit could be varied from 

 0-00007 to 0-00I2 of a henry, and the capacity from 0-0085 

 to 0-0739 of 3 microfarad, and the results obtained afford 

 strong evidence that in the case of a spark discharge in 

 air, at atmospheric pressure, no " shift " in wave-length 

 is produced by variations of self-induction or capacity 



NO. 1849, VOL. 71] 



within the above limits. A further result obtained was 

 that the analogous wave-lengths in the arc and the spark 

 spectra of the same elements are not measurably different. 



STATISTICS OF VARIATION.^ 

 A PAPER consisting mainly of a large number of 

 ■^ elaborate records bearing on the important subject 

 of variation has recently been issued by the Washington 

 Academy of Sciences. The data, which have been collected 

 with much care and industry, cannot fail to be of high 

 interest to all students of evolution. They afford an 

 excellent e.xample of the peculiar value of insect studies in 

 reference to many difficult problems in biology — a point 

 which has lately received fresh emphasis from Prof. 

 Poul ton's valedictory address as President of the Entomo- 

 logical Society of London. 



'(he aulhcrs start with an " Introduction," in which 

 they declare thrir " belief in the marked betterment and 

 effectiveness of practically all variation study when pursued 

 from the point of view of the biometrician " ; adding, how- 

 ever, that " from the writers' point of view the study of 

 variation is a phase of biology, and not of mathematics." 

 Dealing with the special advantages presented by insect 

 data in this inquiry, they assert that the phenomena of 

 complete metamorphosis afford a icady means of distin- 

 guishing " variations which are strictly blastogenic from 

 others which may be in large part acquired." This, it 

 may be remarked, is only true under certain limitations. 

 It is not the case, for instance, as the authors appear to 

 think, that the imaginal colour-patterns of lepidoptera are 

 uninfluenced by the conditions obtaining during individual 

 development. 



Coming now to the main substance of the paper, we 

 find a series of short articles or sections giving statistics of 

 variation in some two dozen species of insects. Among the 

 structures thus dealt with are the venation and costal 

 wing hooks in bees and ants, the venation in gnats, the 

 colour-patterns of sundry beetles, wasps and bugs, the 

 eye-spots of certain butterflies, the tibial spines, tarsal and 

 antennal segments, tactile hairs and elytral striffi of other 

 insects of various orders. In the case of the hive bee it 

 is incidentally shown that the parthenogenetically pro- 

 duced drones are as subject to variation in their wings as 

 are the workers of biparental ancestry. The results are 

 in many cases graphically summarised in the form of the 

 frequencv polygon; and the "mode," "standard devia- 

 tion," "'index of variability,"- and " coeflicient of varia- 

 tion " are duly reckoned and recorded in accordance with 

 approved biometrical methods. It is interesting but not 

 surprising to observe that the frequency curve is usually 

 in fair correspondence with the law of error. 



The paper ends with a section devoted to " general 

 results." Here we think that too much is made of the 

 difticultv of distinguishing between congenital variation 

 and acquired modification. For practical purposes the 

 distinction is usually obvious enough. A little later the 

 authors observe, " The most satisfactory answer to the 

 question of the hereditary transmission of acquired char- 

 acters will come as the result of a quantitative (statistical) 

 study of variations known to be blastogenic compared with 

 a similar study of variations known to be acquired, both 

 studies to be made on complete series of individuals bred 

 under quantitatively determined life conditions." This 

 seems to us somewhat like using a steam-hammer to crack 

 an egg. It is not astonishing to find that there is little 

 or no evidence of differing selection-value in the variable 

 number of spots on the elytra of a ladybird ; but it hardly 

 seems clear that the authors are justified in claiming this 

 fact, together with an apparent change of " mode " 

 between the years 1895 and iqoi, as evidence in favour 

 of "determinate variaUon." Before any such inference 

 can properly be drawn, the question of possible correlation 

 ought at least to be considered. The authors, however, 

 arrive on the whole subject at the satisfactory conclusion 

 that natural selection " is after all a logical necessity and 

 undoubtedly an actual actively-regulative factor " in the 

 formation of species. F- A. D. 



1 " Stutlies of Variation in Insects." By Vernon L. Kelloes and Ruby 

 G Bell, of Leland Stanford Tnnior University. From the Prcceedinss of 

 the Washington Academy of Sciences, vol. vi. (Washington, D.C., 1904 ) 



