3° 2 



SCIENCE-GOSSIP. 



matters are treated under the several headings 



given below. 



Pigments. 



(i) Of direct physiological importance: — 



Haemoglobin : red colouring matter of the blood, 



and respiratory in function. Chlorophyll : 



green colouring matter of most plants and 



contributory to the taking of carbon needed 



in nutrition from carbonic acid gas. 



(2) Derivatives of such pigments : — 



(Most are speedily eliminated from animals' 

 bodies.) Melanin : this dark pigment, colour- 

 ing skin or hair in mammals and setting off 

 structural colours in birds, may be derived 

 from haemoglobin, as are probably the 

 colours of birds' eggs. 



(3) Waste products: — 



Pigments on butterflies' wings, which are 

 modifications of uric acid. Lcpidotic acid. 



(4) Reserve products : — 

 (?) Carmine. 



Or, pigments associated with reserve materials : — 

 Lipochromes (often fat pigments.) Carotin. 



(5) Introduced pigments : — 



Such as chlorophyll derived from food in 

 caterpillars. 

 One is tempted to consider the class of pigments 

 called "lipochromes" in some detail, and with re- 

 gard to which many points of interest are scattered 

 through the book. The lipochromes are characte- 

 rized by their colours varying from yellow to red. 

 When dry they give a blue colour, with concentrated 

 sulphuric or nitric acid ( 2 ) ; and two series are found 

 in animals which do, or do not, as the case may 

 be, form compounds with caustic alkalies. Only the 

 second occurs in plants. These pigments are 

 widely distributed, and, in the vegetable world, not 

 only do they colour flowers like the narcissus and 

 lily, and fruits like the rose-hip and tomato, but, 

 with other pigments, are associated with chloro- 

 phyll : when that colour is lost in autumn they help 

 to give the much-admired tints to many dying leaves. 

 Xanthophyll particularly does this, and may also 

 colour etiolated leaves in which, through the 

 absence of light, no green chlorophyll is produced. 

 It is pointed out that these pigments are very un- 

 stable, and several may occur together ; so that it 

 is difficult to determine whether xanthophyll and 

 etiolin are one and the same. The anthocyans, 

 another series of pigments, apparently derived 

 from tannins, help in colouring the leaves at the 

 approach of winter, and are found in the petals of 

 bluebells and roses, and the fruits of the grape and 

 blackberry. It has been suggested that colour- 



( a ) Bloxam (" Chemistry," p. 666) says if chlorophyll be 

 boiled with alcoholic potash, the solution, when neutralized 

 with hydrochloric acid, gives a yellow precipitate (phyllox- 

 anthin), and the solution retains a blue colouring matter 

 (phyllocyanin), which contains nitrogen, The autumnal 

 colour of leaves is perhaps due to the disappearance of the 

 phyllocyanin. Green leaves assume an autumnal tint 

 when immersed in chlorine." 



ing matters associated with chlorophyll may help 

 in the work of the latter by absorbing some com- 

 ponents of light, as various coloured lights affect 

 the growth of plants for good or evil. 



Among other noticeable points are the remarks 

 upon the occurrence of different colours on 

 occasion in different individuals, and constantly in 

 different sexes of the same species, as well as the 

 cropping up of the same colours in members of 

 the same genus. The author says : — 

 " . . . . It is perhaps universally true that 

 elaborate patterns are dependent, at least in part, 

 upon dark pigments, while bright pigments tend 

 as a rule to be more uniformly distributed. It is 

 difficult to avoid coming to the conclusion that the 

 fact is associated with the insolubility [possibly 

 only due to mordants] of the dark pigments, which 

 will render them on the whole less readily diffused 

 than the more soluble bright-coloured pigments." 

 Again, it is suggested that unspecialized animals, 

 such as many hen birds, may be coloured with a 

 mixture of melanin and lipochrome, which when 

 separated would give vivid orange and black 

 colours as often seen in male birds. 



The arrangement of the many interesting facts 

 that are touched upon under the various headings, 

 based upon the systematic divisions of animals 

 and otherwise, may or may not appear to be 

 erratic, according as the difficulties are appre- 

 ciated. Weakness is displayed in dealing with 

 theories, especially that of "Natural Selection," 

 which, in the introduction, one is told " is no longer 

 the centre of men's thoughts." There is not the 

 unsatisfactory attitude of non-committal which 

 occurs in Mr. Beddard's " Animal Coloration " ; 

 nor is there a stout belief expressed on one side or 

 the other, such as Professor Poulton has accorded 

 to Natural Selection in his " Colours of Animals " ; 

 but the keynote that this theory is no longer 

 fashionable, given in the introduction, is followed up 

 throughout " Colour in Nature " by kicks at an idea 

 which is supposed to be down. Thus, when autumn 

 colours are discussed, we are told that they often 

 display "to an extraordinary degree that beauty 

 and perfectness which we [this must mean the 

 laboratory-made naturalists alluded to elsewhere] 

 are accustomed to regard as the result of the 

 action of Natural Selection." In other places we 

 get the expression — the coloration which " is 

 known as protective " ; and with regard to the 

 case of the drone-fly and bee, one is told that 

 " this has, of course, been described as protective 

 mimicry," and so on. Even when specific diffi- 

 culties are brought forward against " the accept- 

 ance of Natural Selection as the most important 

 factor in the evolution of colour," the author has 

 no other alternatives to offer but such vague ones 

 as she herself says, " many, perhaps justly, find so 

 unsatisfactory." There is a long list of references, 

 which adds considerably to the value of the book. 

 2, The Broadway, Hammersmith, W. 



