Febkxjaet 2, 1906.] 



SCIENCE. 



191 



ference between the sexes (the protoplasmic 

 mass being the same as far as can be observed) 

 it is the female, not the male, that has the 

 larger quantity of nuclear material. This 

 fact has recently been demonstrated by the re- 

 viewer in a dozen different species of hem- 

 iptera, representing eight genera, and the 

 structure 'of the spermatozoa shows that the 

 same is undoubtedly true of many other spe- 

 cies. The difference is here one of nuclear 

 constitution and is irrespective of temporary 

 changes of nuclear volume such as are com- 

 mon to all cells. But even here we can not 

 regard the quantitative difference of the nu- 

 clei as being primarily responsible for the 

 sexual differentiation, for in some of the 

 species of the same group no perceptible dif- 

 ference in this respect exists between the sexes. 

 Without questioning the interest and value 

 of Professor Hertwig's experimental results, it, 

 therefore, seems to us that his theory of sex- 

 production is without real foundation, and 

 that, in the specific form that he has given it, 

 it is untenable. E. B. Wilson. 



ASTRONOMICAL N0TE8. 



THE FIGURE OP THE SUN. 



Two articles by Professor Charles Lane 

 Poor have recently appeared in The Astro- 

 physical Journal dealing with a variation in 

 the figure of the sun. This research comes 

 with special interest at the present 'time, when 

 so many writers are trying to trace relation- 

 ships between various terrestrial phenomena 

 and different forms of solar activity. 



Among the remarkable photographic work 

 done by Rutherfurd was a series of photo- 

 graphs of the sun. These are still of such 

 unimpaired excellence that they permit ad- 

 mirable determinations of the sun's diameter. 

 From a series of such plates extending over 

 the years 1870-1872, measurements were made 

 of the polar and equatorial radii, from a dis- 

 cussion of which it appears that the polar 

 radius is sometimes greater and sometimes less 

 than the equatorial radius. The individual 

 determinations of this difference (polar radius 

 — equatorial radius) vary between + 0.77" 

 and — 0.72", and the means are as follows: 

 for 1870, September 22, + 0.50" ± 0.10", for 



1871, July 19, — 0.32" ± 0.16", and for 1872, 

 July 2, -f 0.22" ± 0.09". There is thus in- 

 dicated a change in the relative values of the 

 polar and equatorial diameters of the sun. 

 This conclusion, if true, is of great impor- 

 tance, and it is not strange that Professor' 

 Poor desired to verify his results by reference 

 to other and independent determinations of 

 the form of the sun. 



A large number of heliometer measurements 

 of the diameter of the sun were available from 

 a very thorough discussion, by Dr. Auwers, of 

 the transits of Venus, in 1874 and 1882. Dr. 

 Auwers reached the conclusion that the diam- 

 eter of the sun at distance unity is 1,919.26", 

 and that the polar diameter slightly exceeds 

 the equatorial diameter. This difference,, 

 however, was attributed by him to the personal 

 equation on the part of the observers between 

 measures of vertical and horizontal diameters. 

 The observations as discussed by Auwers gave 

 no indication of a variation in the relative 

 values of the different diameters, but were 

 rearranged in a form suitable for this dis- 

 cussion by Professor Poor. 



Measurements were also made of a short 

 series of photographs of the sun taken at 

 ISTorthfield by Dr. Wilson. Both the heliom- 

 eter determinations and the Northfield pho- 

 tographs seem to confirm the results obtained 

 from the Rutherfurd photographs. Professor 

 Poor thus sums up his conclusions : 



The present investigation would seem to 'show, 

 therefore, that the ratio between the polar and 

 equatorial radii of the sun is variable, and that 

 the period of this variability is the same as the 

 sun-spot period. The sun appears to be a vibra- 

 ting body whose equatorial diameter, on the 

 average, slightly exceeds the polar diameter. At 

 times, however, the polar diameter becomes equal 

 to and even greater than the equatorial — the sun 

 thus passing from an oblate to a prolate spheroid. 



In a second paper Professor Poor extended 

 his investigations to include the elaborate 

 heliometer determinations! of the sun's dimen- 

 sions, carried on at Gottingen by Shur and 

 Ambronn. These observations covered a full 

 sun-spot period, from 1890-1902. Ambronn, 

 who discussed the observations, gave his spe- 

 cial attention to the mean diameter of the 

 sun, sb that again it became necessary to 



