Feb. 6, 1890] 



NATURE 



3^0 



effected only by diminishing its height ; in which case it 

 would hardly correspond to his description of its form as 

 that of an egg cut in two. The question can only be 

 fairly tested by the weighment of a model constructed as 

 nearly as possible in accordance with Tavernier's figure, 

 and of such lateral dimensions as to be capable of in- 

 cluding the Koh-i-noor. It may be that such a model, of 

 the specific gravity of the diamond, would be found much 

 to exceed Tavernier's reported weight of the stone, in ' 

 which case the importance of his figure as an item of 

 evidence, would be greatly invalidated. 



Whatever may be the final outcome of this controversy? 

 Mr. Ball has done a good service to literature and science 

 in re-translating Tavernier's work, in its careful editing, 

 and in throwing light on much that has hitherto remained 

 obscure. The result will certainly be that which he has 

 anticipated, the vindication of Tavernier's claim "to be 

 regarded as a veracious and original author." 



H. F. B. 



OUR BOOK SHELF. 



Star Land. By Sir Robert S. Ball, LL.D., F.R.S. 

 (London : Cassell and Co., 1889.) 



The author of this work is now so well known as a 

 popular expounder of astronomical subjects that it is 

 quite sufficient praise of his new book to say that it fully 

 sustains his reputation. The book is described as " talks 

 -with young people about the wonders of the heavens," 

 being founded chiefly on notes taken at his courses of 

 juvenile lectures at the Royal Institution. Astronomy 

 gives plenty of scope for the exercise of the imagination, 

 and Dr. Ball takes full advantage of this. The book 

 abounds with anecdotes and homely illustrations, calcu- 

 lated to impress the facts on the memory as well as to 

 ■excite wonder at them. The startling figures dealt with 

 in astronomy are, as usual, converted into railway train 

 notation, and otherwise illustrated. One new illustration 

 of the distances of the stars is that it would take all the 

 Lancashire cotton factories 400 years to spin a thread 

 long enough to reach the nearest star at the present rate 

 of production of about 155,000,000 miles per day. The 

 irregularities in the motion of Encke's comet are explained 

 in an interesting dialogue between the " offending comet" 

 and the astronomer, in which the comet explains that 

 his delay was due to the fact that Mercury was "meddle- 

 some." 



The only disappointing parts of the book are those 

 which deal with astronomical physics. One point not 

 sufficiently insisted upon is the now generally acknow- 

 ledged meteoritic constitution of comets ; a connection is 

 certainly suggested, but that comets are now supposed to 

 be simply dense swarms of meteorites is not stated at all. 

 Nebulae, again, are described as " masses of glowing gas," 

 notwithstanding the recent researches on the subject. 

 The theory that meteorites are the products of ancient 

 terrestrial volcanoes is also still adopted by Dr. Ball, 

 without any consideration of the objections to such a view. 



The book is well illustrated, and will undoubtedly 

 awaken an interest in the subject in all intelligent 

 readers. 



The Magic Lantern : its Co7tstruction and Use. By a 

 Fellow of the Chemical Society. (London : Perken, 

 Son, and Rayment.) 



The third edition of this little book has been issued, 

 and will be exceedingly useful to those who work with 

 the lantern. Descriptions are given of the various 

 lights used in lanterns, from the oil lamp to the electric 

 arc ; the methods of making simple slides are entered 



into, and a few experiments, illustrative of elementary 

 scientific principles, are well included. The work is 

 thoroughly practical ; none of the little details so 

 necessary to beginners have been omitted, whilst many 

 of the hints it contains may be of service to all who use 

 this optical instrument, whether it be for lecture purposes 

 or for recreation only. 



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. ] 



Acquired Characters and Congenital Variation. 



I PO not see that the Duke of Argyll's last letter in any way 

 strengthens his position. The questions at issue with regard to 

 evolution are now, I believe, thoroughly understood by biologists. 

 Nothing, in my opinion, can solve them in the direction the 

 Duke desires but the evidence of fact. And that, I can only 

 repeat, is precisely what is not forthcoming. I am equally of 

 opinion that the discussion has been worn threadbare. I should 

 not myself have interfered in it, had it not seemed desirable to 

 show that the motives attributed by the Duke to those who 

 accept Darwinian principles were destitute of foundation. 



This part of his position the Duke does not attempt to defend. 

 As to the rest he merely restates what he has said before. His 

 remarks fall under two heads, and I shall content myself with 

 the briefest possible comment upon these. 



(i) Acquired Characters. — The Duke gives what I presume 

 he intends as a logical proof of the theorem that acquired 

 characters are inherited. It may, I think, be formally expressed 

 as follows : — 



" It is always possible to assert " that acquired characters are 

 developed latent congenital characters. 



It is admitted that congenital characters are inherited. 



. ■ , Acquired characters are inherited. 



It will be observed in the first place that this is a mere a 

 priori argument. And next that, while it is not denied by Dar- 

 winians that the organism is a complex of congenital tendencies, 

 limitations, and possibilities, this is entirely beside the question. 

 From Lamarck to Darwin, Weismann, and Lankester, the mean- 

 ing of "acquired characters" has been clearly defined. They 

 are those changes of hypertrophy, extension, thickening, and the 

 like, which are obviously due to the direct physical action of the 

 environment on the body of the individual organism. It was 

 these changes which Lamarck asserted were transmitted to the 

 offspring ; and it is this transmission which it is now maintained 

 needs demonstration as a fact. 



Let me give another illustration, I read the other day in the 

 newspapers that the police of Paris have carried out an extremely 

 interesting investigation. They have carefully ascertained the 

 recognizable changes in the normal human organism produced 

 by the prolonged pursuit of any particular occupation. The 

 object was to obtain data for the identification of unknown dead 

 bodies. The changes proved more numerous and characteristic 

 than could have been supposed. They supplied, in fact, diagnostic 

 marks by which the occupation of the individual could be 

 accurately inferred. It seems to me impossible to have a more 

 admirable case of the direct action of external conditions. I 

 ask. Is there any reason to suppose that these acquired characters 

 would be transmitted ? 



This appears to me an extremely plain issue, as it is certainly 

 an extremely important one. There is not the least reluctance 

 on the part of Darwinians to face it squarely. But the Duke 

 appears to me to deliberately evade it. 



(2) Prophetic Germs. — It seems to me that we are somewhat 

 at cross- purposes. The Duke admits that I have correctly 

 quoted him as saying : "All organs do actually pass through 

 rudimentary stages in which actual use is impossible." When 

 Prof. Lankester challenged the Duke to produce a single in- 

 stance, he guarded himself by the remark: "The stages here 

 alluded to are — if I understand correctly — ancestral stages, not 

 stages in the embryological development of the individual." 

 The Duke has never repudiated, as far as I am aware, that 

 limitation of his meaning, if it be a limitation. And as he has 



