November 8, 1900J 



NATURE 



29 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.'^ 



Secondary Sexual Characters. 

 In his article on " Antelopes and their Recognition Marks" 

 in the number of Nature dated October ii, Mr. R. I. Pocock 

 suggests that the darker colour of the males in certain species is 

 the outcome or accompaniment of "male katabolism." As 

 generally used, this term seems to denote some peculiarity 

 universally associated with the male sex and giving rise to male 

 peculiarities, so that a character which is the outcome of male 

 katabolism does not require to be explained by the theory of 

 sexual or that of natural selection. This is the sense in which 

 Geddes and Thomson use the term in their " Evolution of 

 Sex " : " So brilliancy of colour, exuberance of hair and feathers, 

 activity of scent glands, and even the development of weapons, 

 are not and cannot be explained by sexual selection, but in 

 origin and continued development are outcrops of a male as 

 opposed to a female constitution." But if male katabolism is 

 always associated with the male sex, how is it that there are so 

 many species in which there are no secondary differences 

 between male and female, no outcrops of male katabolism ? 

 Either male katabolism, as something different from female 

 katabolism, does not exist in the males of all species, or it 

 sometimes exists without producing any visible effect. 



It is therefore evident that male katabolism in the kinetic, 

 and not merely the potential, state occurs only in the males of 

 those species which exhibit sexual dimorphism. After all, 

 katabolism is only a name for certain phases of physiological 

 activity, and we thus arrive at the hypothesis that male sexual 

 peculiarities are the result of the peculiar katabolism of the 

 males that possess them. Now we have a reason for such 

 peculiar katabolism, or metabolism, in the special nervous and 

 muscular activity which is observed in the sexual habits of those 

 males which possess secondary sexual characters. This excite- 

 ment and muscular exertion involves an increase of the meta- 

 bolism, which goes far to explain, among other things, an 

 increased production of pigment, and the consequent darker or 

 more intense colouring of the males in many instances. The 

 special metabolism is thus due to the habits of life, to external 

 conditions, not to any quality necessarily associated with male 

 sexuality. 



It seems to me that, regarding the subject from the point of 

 view I have indicated, we may arrive at the explanation of the 

 darker colour of certain male antelopes, and also of the presence 

 of horns in the males only. If the peculiarities of the male, in 

 particular its colour, are thus the necessary results of physio- 

 logical processes, they are sufficiently explained, without the 

 additional suggestion that the hornless female has been com- 

 pelled to adhere to the normal protective colouring of the group, 

 while the males, by reason of their horns and superior strength, 

 have been able to dispense with that advantage. Moreover, 

 Mr. Pocock maintains, in other cases in which horns are 

 developed in the male only, that the markings of the male are 

 protective, for instance, in the kudu. J. T. Cunningham. 

 Penzance, October 27. 



The Value of the Cylinder Function of the Second 

 Kind for Small Arguments. 



In investigating the propagation of electrical oscillations along 

 cylindrical conductors, the " K(, " function, which satisfies the 

 Bessel's equation and vanishes at infinity, is used to express the 

 vectors outside the wire. Under the conditions of the problem 

 the approximate value of this function for very small arguments 

 is needed. I wish to point out an error in this value, which 

 occurs in all three important memoirs in which the subject has 

 been discussed — viz. those of Prof. J. J. Thomson (" Recent 

 Researches," p. 263), Sommerfeld {IVied. Ann., Ixvii. p. 245, 

 1899) and Mie (Ann. d. Physik, ii. p. 211, 1900), an error 

 which can, I think, be traced to a misprint in Heine's " Kugel- 

 functionen." 



The formula given by Heine (vol. i. p. 245) yields as the 



approximate value Kq( j:) = log - - C -f \Tti. 



C is Euler's constant 05772 . . . but in the statement of its 

 NO. 1619. VOL. 63] 



value which follows - C is printed for C. This mistake, whi^dl . 

 is not corrected in the errata, is pointed out in the " Treatise'?; 

 of Gray and Mathews (p. 88, footnote). ; 



ii 

 If we put £''=■5772, we have Ko(j:) = log _. In tht' 



yx _ .;;., 



papers referred to, the 7 appears in the numerator, which wpuld, 

 correspond to the alteration in the sign of C. In Prof. Thomson's, 

 work the i in the numerator is omitted. 



The error has no effect on the theoretical conclusions reached 

 in the papers. The numerical results given by Sommerfeld and 

 Mie are subject to corrections, which will not, however, affect 

 the order of magnitude. For example, the attenuation constants 

 worked out by Sommerfeld are something like 10 per cent, too 

 small. W. B. Morton. 



Queen's College, Belfast, October 25. 



Mosquitoes and Diseases. 



At p. 627 of your issue of October 25, while noticing Profs. 

 Grassi and Noe's observations on Filaria immitis, you say 

 " Malaria is riot the only disease which is propagated by 

 mosquitoes." May I remind your readers of Dr. Patrick 

 Manson's important observations on Filaria sanguinis-hominis, 

 originally communicated to the ' Linnean Society by Dr. Cob- 

 bold, on March 7, 1878 ("On the Development of Filaria 

 sanguinis-hominis, and on the Mosquito considered as a 

 Nurse": Jottrn. Linn. Soc. Zool., xiv., pp. 304-311), and 

 amplified later in a paper communicated on March 6, 1884 

 (" The Metamorphosis of Filaria sanguinis-hominis in the 

 Mosquito" : Trans. Linn. Soc. Zool., ser. 2, vol. ii., pp. 367- 

 388, pi. xxxix.)? W. F. KiRBY. 



British Museum (Natural History), London, S.W., 

 October 30. 



OUR STELLAR SYSTEM. 



IN a recently published volume ^ I endeavoured lo 

 bring together the facts relating not only to the 

 distribution of stars generally, but to those which the 

 spectroscope has more recently brought before us touch- 

 ing the distribution of the various chemical groups of 

 stars. One of the interesting results of the inquiry was 

 that the Milky Way, which dominates the general dis- 

 tribution, is also the region of the heavens in which un- 

 doubted nebulae giving us bright-line spectra most do 

 congregate. Nor is this all. Those so-called " stars," 

 in the spectra of which bright lines are seen, " bright- 

 line stars " and " new stars," which I have elsewhere 

 shown are nebulae or stars associated with nebulas, are 

 also almost entirely confined to the Milky Way. The 

 new spectroscopic knowledge, although so priceless to the 

 student of the chemistry of space, tells us, however, 

 nothing as to the distances of the bodies from us ; it 

 only tells us that they lie in the galactic plane. If, 

 however, we combine with the chemical facts the results 

 obtained by Monck, Kapteyn and others touching the 

 proper motions of the various kinds of stars as defined 

 by their spectra, the results we obtain are most definite. 

 Dealing with the stars generally, it may be stated that 

 the latest inquiries have suggested the following very- 

 general classification of stars depending upon temper- 

 ature : — 



Highest Temperature. 



ry X r Proto-hydrogen stars. 



Gaseous starss /~.i •. ' '^ . 



\^Cleveite-gas stars. 



Proto-metallic stars. 



Metallic stars. 



Stars with fluted spectra. 



Lowest Temperature. 



Now to make the most general statement, we find that 

 the gaseous stars are not only confined to the Milky Way, 

 but they are the most remote in every direction, in every 

 galactic longitude ; all of them have the smallest proper 

 motion. The metallic stars are nearest to us, but they 

 are not confined to the Milky Way. The proto-metallic 

 stars are intermediate between these two great g^roups,. 



1 " Inorganic ETOludatl," pp. 124-143. 



