5^4 



NATURE 



\April 3, 1890 



produced in oxygen gas at ordinary temperatures and pressures, 

 but on warming the oxygen, both the ozone and the glow are 

 formed. On passing ozone into oxygen at temperatures at 

 which phosphorus refuses to glow, 'the phophorus at once 

 becomes luminous, oxygen is absorbed, and the characteristic 

 cloud of oxide is produced, and the effect continues so long as 

 the supply of ozone is maintained. A drop of ether at once 

 extinguishes the glow. The ether is in all probability converted 

 into vinyl alcohol with simultaneous formation of hydrogen per- 

 oxide by the reaction indicated by Poleck and Thiimmel : — 



CH3CII0 



ch..ch; 



)0 + O., = 



CH.,CHOH 



3 ~ CHXHOH 



HO 

 HO 



}■ 



A. W. Wright has shown that formic, acetic, and oxalic acids 

 are also formed by the action of ozonized oxygen on ether. 



Phosphorus combines with oxygen in several proportions, and 

 the study of the mode of formation and properties of these 

 oxides is calculated to throw light upon the nature of the che- 

 mical process which attends the glow of phosphorus. Certain 

 of these oxides have recently been the subject of a considerable 

 amount of study in the chemical laboratories of the Normal 

 School of Science. When phosphorus is slowly burned in air, 

 there is produced a considerable quantity of a volatile substance, 

 having a charactefristic garlic-like smell, which solidifies, when 

 cooled, in beautiful arborescent masses of white crystals. It melts 

 at about 23°, and boils at 173°. In a sealed tube kept in the dark, 

 it may be preserved unchanged, but on exposure to light, and 

 especially to bright sunshine, it rapidly becomes deep red. It 

 slowly absorbs oxygen at the ordinary temperature and pressure, 

 but from the mode in which the solid product of the reaction 

 (PgOj) is deposited, it is evident that the union only takes place 

 between the vapour of the oxide and the oxygen gas. Under 

 diminished pressure the act of combination is attended with a 

 glow which increases in brilliancy if ozone be present. On 

 compressing the oxygen, the glow ceases. No ozone is formed 

 during the act of oxidation. The degree of rarefaction needed 

 to initiate the glow depends upon the temperature of the oxide 

 — the warmer the oxide the less is the diminution of pressure 

 required. By gradually warming the oxide, the luminosity 

 steadily increases both in area and intensity, until at a certain 

 temperature the mass ignites. The change from glow to actual 

 flame is perfectly regular and gradual, and is unattended with 

 any sudden increase in brilliancy. In this respect the process 

 of oxidation is analogous to the slow and barely visible burning 

 of fire-damp which is sometimes seen to occur in the Davy 

 lamp, or to the slow combustion of ether and other vapours, 

 which has been specially studied by Dr. Perkin. Other in- 

 stances of what may be called degraded combustion are known 

 to chemists. Thrown into warm oxygen, the substance bursts 

 into flame at once and burns brilliantly, and it also takes fire in 

 contact with chlorine. Alcohol also ignites it, and when it is 

 warmed with a solution of potash or with water it evolves spon- 

 taneously inflammable phosphoretted hydrogen. In contact with 

 cold water it suffiers only a very gradual change, and many days 

 may elapse before even a comparatively small quantity is dissolved. 

 This substance has long been known ; it was discovered, in fact, 

 by the French chemist Sage, but its true nature has only now been 

 determined. Its chemical formula is found to be P4O,; ; hence 

 its composition is similar to that of its chemical analogue, 

 arsenious oxide. 



The study of the properties of this remarkable substance 

 enables us to gain a clearer insight into the nature of the che- 

 mical process attending the glow of phosphorus. When phos- 

 phorus is placed in oxygen, or in an atmosphere containing 

 oxygen, under such conditions that it volatilizes, the phosphorus 

 oxidizes, partly into phosphoric oxide and partly into phosphor- 

 ous oxide. Ozone is formed, possibly by the reaction already 

 indicated, and this reacts upon the residual phosphorus vapour 

 and the phosphorous oxide with the production of the luminous 

 effect to which the element owes its name. The glow itself is 

 nothing but a slowly-burning flame having an extremely low 

 temperature, caused by the chemical union of oxygen with the 

 vapours of phosphorus and phosphorous oxide. By suitable 

 means this glow can be gradually augmented, until it passes by 

 regular gradation into the active vigorous combustion which we 

 ordinarily associate with flame. Many substances, in fact, may 

 be caused to phosphoresce in a similar way. Arsenic, when 

 gently heated, glows in oxygen, and sulphur may also be ob- 

 served to become luminous in that gas at a temperature of about 

 200°. 



''BEFORE AND AFTER DARWIN." 



r\^ Tuesday, March 25, Prof. G. J. Romanes, F.R.S., con- 

 ^^ eluded his course of between thirty and forty lectures, which, 

 under the above title, he lias been deliveiing at the Royal 

 Institution during the last three years. At the close of the 

 lecture he announced his intention of publishing the whole 

 course in November next, and distributed among the audience 

 printed slips, conveying in the form of twelve propositions the 

 "general conclusions " to which his lectures for the present year 

 have led. The following is a copy of this printed slip : — 



(1) "Natural selection has been the main, but not the ex- 

 clusive means of modification," both as regards species and all 

 the higher taxonomic divisions. 



(2) Of the other factors of organic evolution it is not improb- 

 able that we are still to a large extent ignorant. Whether, or to 

 what extent, sexual selection and the I.amarckian principles 

 have co-operated, is a matter with which I am not specially 

 concerned ; but I think there is abundant evidence to establish 

 the high importance in this connection of amixia, or independent 

 variability, — at all events as regards the evolution of species. 



(3) Natural selection is primarily a theory of the cumulative 

 development of adaptations wherever these occur, and therefore 

 is only incidentally, or likewise, a theory of the o.igin of species 

 in cases where allied species differ from one another in respect 

 of peculiar characters, which are also adaptive characters. 



(4) Hence it does not follow from the theory of natural 

 selection that all species — much less all specific characters — 

 must necessarily have owed their origin to natural selection, 

 since it cannot be proved deductively from the theory that no 

 "means of modification " other than natural selection is com- 

 petent to produce such slight degrees of modification as go to 

 constitute diagnostic distinctions between closely-allied species ; 

 while, on the other hand, there is an overwhelming mass of 

 evidence to prove the origin of " a large proportional number of 

 specific characters " in causes of modification other than natural 

 selection. 



(5) Even if it were true that all species and all specific characters 

 must necessarily owe their origin to natural selection, it w ould 

 still remain illogical to define the theory of natural selection as 

 indifferently a theory of species or a theory of adaptations ; for, 

 even upon this erroneous supposition, specific characters and 

 adaptive characters would remain very far indeed fiom being 

 conterminous — by far the larger number of adaptations which 

 occur in organic nature being the common property of many 

 species. 



(6) In no case can natural selection have been the cause of 

 mutual infertility between allied or any other species. 



(7) Without isolation, in the sense of either separate or 

 segregate breeding, organic evolution is in no case possible ; 

 and hence, heredity and variability being given, the whole 

 theory of organic evolution may be regarded as a theory of the 

 causes and conditions which have led to isolation, or the mating 

 of similar variations to the exclusion of dissimilar. 



'8) Natural .'election is one among sundry distinct kinds of 

 isolation, and presents in this relation the following peculiari- 

 ties : [a) the isolation is with reference to superiority of filne.'S ; 

 (l>) is effected by destruction of the excluded individuals ; and 

 {c) unless assisted by some other kind of isolation, can only 

 effect monotypic as distinguished from polytypic evolution. 



(9) It is a general law of organic evolution that the number 

 of possible directions in which divergence may occur can never 

 be more than equal to the number of cases of efficient isolation ; 

 but, excepting natural selection, any one kind of isolation need 

 not necessarily require the co-operation of another kind in orderf 

 to create an additional case of isolation, or to cause polytypic asj 

 distinguished from monotypic evolution. 



(10) Where common areas are concerned, the most general' 

 and most efficient kind of isolation has been the physiological — I 

 and this whether the mutual infertility has been the antecedent! 

 or the consequent of morphological changes on the part of! 

 the types concerned, and whether or not these changes are of an| 

 adaptive character. I 



(11) This form of isolation — which in regard to incipient] 

 species I have called physiological selection — may act either! 

 alone, or in conjunction with other kinds of isolation on 

 common areas: in the former case its agency is of most im-i 

 portance among plants and the lower classes of animals ; in the: 

 latter case its importance consists in its greatly intensifying the; 

 segregating power of whatever other kind of isolation it may bej 

 with which it is associated. 



