April 1 6, 1874] 



NATURE 



461 



them, by attracting in like manner also the attention of insects, 

 which, visiting the flowers for their own profit, at tlie same time 

 unconsciously bring to the plant the great advantage of cross- 

 fertilisation. Hence we understand that l>right-flow-ered varieties, 

 whenever produced by any cause, might be preserved by natural 

 selection, and at last remain the only survivors among all the con- 

 currents of the same species. Thus, the occasional appearance 

 of gaily -coloured varieties granted as a matter of fact, and the 

 peculiarities of colour supposed to be hereditable, we are 

 enablfd by Darwin's theory to explain the variety of 

 colours met with in flowers. But we should always bear in mind 

 that we are at present quite ignorant of the chemical processes 

 by which certain colours are produced in the flowers, and of 

 the physical or organic causes by wliich these chemical pro- 

 cesses were effected when they first ajipeared and are effected 

 in every subsequent generation. Reflecting on the first origin of the 

 adaptation of flowers to the cross-fertilisation by insects, and con- 

 sidering that the oldest and most primitive phanerogamous plants 

 wliich slill exist, the Gymnosperma^ are exclusively fertilised by 

 the wind (are ancmophiloiis], whilst the enormous majority of 

 Angiosperma; is provided with flowers adapted to cross-fertilisa- 

 tion by insects {eiitomopliilous), we cannot doubt that the original 

 manner of fertilisation of phanerogamous plants was fertilisa- 

 tion by the wind, and that the first plants which adapted their 

 flowers to cross-fertilisation by insects were anemophilous ones, 

 either Gymnosperma; or the next descendants of them. Never- 

 theless the flowers of many Gymnospermaa (Abietina;) present a 

 beautiful colour, which attains its culmination during the disse- 

 minating of the pollen.* This beautiful colour is aDparently 

 neither of any use to these plants, which are regularly cross- 

 fertilised by the wind, nor can have been inherited from an- 

 cestors to which it was useful. We may therefore also in this 

 case, without hesitation, regard the colour as a merely accidental 

 phenomenon, which, secondarily produced by the more active 

 chemical processes during the time of flowering, disappears again 

 in the same degree as the intensity of development decreases in 

 the cones. Probably the gaily-coloured perianths of the cntomo- 

 philons Angifjsperma? have originated in a similar manner. 



Independently of possible physical effects, natural selection is 

 evidently without any influence as to colouis, imless animals are 

 a'tracted or repelled by them. Consequently not only the first 

 origin of bright-coloured flowers, but also the change ot colour in 

 the flowers after the ovaries are set, is altogether foreign to 

 the effects of natural selection. It is as indifferent to an eniomo- 

 philous plant wdiether its flowers, after having been (ertilised, 

 grow paler or darker, as it is to an anemophilous plant v/hether 

 Its flowers are attractive to insects or not. In most cases, indeed, 

 flowers change while fading into palercnd less conspicuous colours, 

 but often also their colour remains unaltered or even grows more 

 conspicuous. Old flowers of Mdampyyu'ii pratcnsc, for instance, 

 which, not having been cross- fertilised by insects, regu- 

 larly fertilise themselves, are always reddish-yellow, whilst 

 younger ones are yellow. 



As to Fumaria caprcohiin, alluded to in Mr. Moggridge's 

 letter (Nature, vol. ix. p. 423) I have neverhad the opportunity of 

 observingits flowers myself, but from Ilildebrand'saccount ("J ahrb. 

 f. wi>s?n.sch. Bj!." vii. p. 452) I believe that it is restricted 

 to regular self-fertilisation, cross-fertilisation by insects not, in- 

 deed, being impossible, but taking place very exceptionally ; for 

 it has lost, probably from permanent disuse, the elasticity of the 

 cap formed by the inner petals, which in other fumitories 

 secures cross-fertilisation in case of the repeated visits of insects. 

 If this presumption of mine be right, it would the more explain 

 Mr. Moggridge's observation ; for in this case the colour of the 

 flowers ol this fumitory, inherited from ancestors to which it was 

 quite useful, would be almost useless to this degener.ited descen- 

 dant, and therefore almost withirawn fromjihe influence for 

 natural selection. Hermann MOller 



Lippstadt, April 4 



Conference for Maritime Meteorology 

 Some of your readers may have noticed in the Report of the 

 Proceedings of the Meteorological Congress at Vienna that it 

 was decided to be advisable to convene a fresh Conference for 

 maritime meteorology, in order to reconsider the decisions of the 

 Brussels Conference m 1S53. 



The matter was handed over to the Permanent Committee, 



* See Str.^ssljurger's 

 pp J4<)-26i. 



' Yenr.isclie Zeltschrift," vi. band, 2 heft. 



and by them delegated to a sub-committee composed of the fol- 

 lowing members : — 



Prof. Buys Ballot (Holland) 



Prof. Mohn (Norway) 



Capt. E. Mouchez (France) 



Dr. G. Neumayer (Germany) 

 with myself. 



The sub-committee liave nearly decided on a form of pro- 

 gramme for the proceedings, and there are hopes that the Con- 

 ference will meet in London in the month of -\ugust or so. 

 Endeavours will probably be made to induce H.M.'s Government 

 to issue the invitations, and thereby to give an official character 

 to the Conference. Robert H. Scott 



Herbert Spencer and a priori Truths 



Absence from town has delayed what further remarks I have 

 to make respecting the disputed origin of physical axioms. 



The particular physical axiom in connection with which the 

 general question was raised, was the Second Law of Motion. 

 It stands in the Priacipia as follows : — 



" Tki: alteration of molion is ever proportional to the viotive 

 force impressed ; and is made in the direction of the right line in 

 lohich that force is impressed. 



" If any force generates a moti in, a double force will generate 

 double the motion, a triple farce triple the motion, whether that 

 force be impressed altogether and at once, or gradually and suc- 

 cessively. And this motion (being al A'ays directed the same way 

 with the generating force), if the body moved before, is added 

 to or subducted from the former motion, according as they 

 directly conspire with or are directly contrary to each other ; or 

 obliquely joined, when they are oblique, so as to produce a new 

 motion compounded from the determination of both." 



As this, like each of the other laws of motion, is called an 

 axiom ;* as the paragraph appended to it is simply an amplifica- 

 tion, or re-statement in a more concrete form ; as there are no 

 facts named as bases of induction, nor any justifying experiment ; 

 and as Newton proceeds forthwith to draw deductions, it was a 

 legitimate inference that he regarded this truth as a priori. My 

 sta'ement to this effect was based on the contents of the Pnncipia 

 itself ; and I think I was warranted in assuming that the nature 

 of the laws of motion, as conceived by Newton, was to be thence 

 inferred. 



The passages quo'ed by the British Quarterly Jici'uioer from 

 Newton's correspondence, which were unknown to me, show that 

 this was not Newton's conception of them. Thua far, then, my 

 opponent has the best of the argumen':. Several qualiiying con- 

 siderations have to be set down, however. 



(i) Clearly, the statemen's contained in the Principia do not 

 convey Newton's conception ; otherwise there would have been 

 no need for his explanations. The passages quoted prove that 

 he wished to exclude these cardinal truths from the class of hypo- 

 theses, which he said he did not make ; and to do this he had to 

 define them. 



(2) By calling them axioms, and by yet describing them as 

 principles "deduced imm phenomena," he makes it manifest that 

 lie gives the word axiom a sense widely unlike the sense in 

 which it is usually accepted. 



(3) Further, the quotations fail to warrant the statement that 

 the laws of motion are proved true by the truth of the Principia. 

 For if the fulfilment of asronomical predictions made in pursu- 

 ance of the Principia is held to be the evidence "on which they 

 chiefly rest to this day," then, until thus justified, they are un- 

 questionably hypotheses. Yet Newton says they are not hypo- 

 theses. 



Newton's view may be found without seeking for it in his 

 letters : it is contained in the Principia itself. The scholium to 

 Corollary VI. begins thus : — 



" Hitherto I have laid down such principles as have been re- 

 ceive.l by mathematitians, ..nd are confnited by abundance of 

 experiments. By the two first Laws and the two first Corolla- 

 ries, Galileo discovered that the descent of bodies observed the 

 duplicate ratio of the time, and that the motion of projectiles was 

 in the curve of a parabola ; experience agreeing with both," &c. 



Now as this passage precedes the deductions constituting the 

 Principia, it shows c .nclusiv.dy, in the first place, that Newton 

 did not think " the whole of the Principia was the proof" of the 



* It is true that in Newton's time, " axiom " had not the same rigorously 

 defined meaning as now ; but it suffices tor my argument that, standing un- 

 proved as a basis for physicat deductions, it bears just the same relation to 

 them that a mathematical axiom does to mathematical ded 



