Jan. 8, 1880] 



NATURE 



237 



The theory now proposed is a considerable modification 

 of this view, for it supposes that the rupture of the central 

 body did not take place until it was partially consolidated, 

 and had attained nearly its present dimensions. 



I do not pretend, in these remarks, to have thoroughly 

 discussed the cases of the other planets, and have only 

 drawn attention to a few salient features ; in the paper 

 itself the subject is considered at greater length. It will, 

 however, I think, be admitted that the theory agrees with 

 some remarkable facts in the solar svstem. 



G. H. Darwin 



THE SEXUAL COLOURS OF CERTAIX 

 BUTTERFLIES 



DR. SCHULTE, of Fiirstenwalde, has called my 

 attention to the beautiful colours which appear on 

 all four wings of a butterfly, the Diadema bolina, when 

 looked at from one point of view. The two sexes of this 

 butterfly differ widely in colour. The wings of the male, 

 when viewed from behind, are black with six marks of 

 pure white, and they present an elegant appearance ; 

 but when viewed in front, in which position, as Dr. 

 Schulte remarks, the male would be seen by the female 

 when approaching her, the white marks are surrounded 

 by a halo of beautiful blue. Mr. Butler, also showed me 

 in the British Museum an analogous and more striking 

 case in the genus Apatura, in which the sexes likewise 

 differ in colour, and in the males the most magnificent 

 green and blue tints are visible only to a person standing 

 in front. Again with Ornithoptera the hind wings of the 

 male are in several species of a fine golden yellow, but 

 only when viewed in front ; this holds good with O. ma- 

 gellattus but here we have a partial exception, as was 

 pointed out to me by Mr. Butler, for the kind wings 

 when viewed from behind change from a golden tint into 

 a pale iridescent blue. Whether this latter colour has 

 any special meaning could be discovered only by some one 

 observing the behaviour of the male in its native home. 

 Butterflies when at rest close their wings, and their lower 

 surfaces, which are often obscurely tinted, can then alone 

 be seen ; and this it is generally admitted, serves as a 

 protection. But the males, when courting the females, 

 alternately depress and raise their wings, thus displaying 

 the brilliantly coloured upper surface ; and it seems the 

 natural inference that they act in this manner in order 

 to charm or excite the females. In the cases above 

 described this inference is rendered much more probable, 

 as the full beauty of the male can be seen by the 

 female only when he advances towards her. We are 

 thus reminded of the elaborate and diversified manner in 

 which the males of many birds, for instance the peacock, 

 argus pheasant, &c, display their wonderful plumage to 

 the greatest advantage before their unadorned friends. 



The consideration of these cases leads me to add a few 

 remarks on how far consciousness necessarily comes 

 into play in the first acquirement of certain instincts, in- 

 cluding sexual display ; for as all the males of the same 

 species behave in the same manner whilst courting the 

 female, we may infer that the display is at least now 

 instinctive. Most naturalists appear to believe that every 

 instinct was at first consciously performed ; but this seems 

 to mean erroneous conclusion in many cases, though true 

 in others. Birds, when variously excited, assume strange 

 attitudes and ruffle their feathers ; and if the erection of 

 the feathers in some particular manner were advan- 

 tageous to a male whilst courting the female, there does 

 not seem to be any improbability in the offspring which in- 

 herited this action being favoured ; and we know that odd 

 tricks and new gestures performed unconsciously are often 

 inherited by man. We may take a different case (which 

 I believe lias been already advanced by some one), that of 

 young ground birds which squat and hide themselves 

 when in danger immediately at tcr emerging from the egg ; 



and here it seems hardly possible that the habit could have 

 been consciously acquired just after birth without any 

 experience. But if those young birds which remained 

 motionless when frightened, were oftener preserved from 

 beasts of prey than those which tried to escape, the habit 

 of squatting might have been acquired without any 

 consciousness on the part of the young birds. This 

 reasoning applies with special force to some young wading 

 and water birds, the old of which do not conceal them- 

 selves when in danger. Again a hen partridge when there 

 is danger flies a short distance from her young ones and 

 leaves them closely squatted ; she then flutters along the 

 ground as if crippled, in the wonderful manner which is 

 familiar to almost every one; but differently from a really- 

 wounded bird, she makes herself conspicuous. Now i 

 is more than doubtful whether any bird ever existed with 

 sufficient intellect to think that if she imitated the actions 

 of an injured bird she would draw away a dog or other 

 enemy from her young ones ; for this presupposes that 

 she had observed such actions in an injured comrade and 

 knew that they would tempt an enemy to pursuit. Many 

 naturalists now admit that, for instance, the hinge of a 

 shell has been formed by the preservation and inheritance 

 of successive useful variations, the individuals with a 

 somewhat better constructed shell being preserved in 

 greater numbers than those with a less well constructed 

 one ; and why should not beneficial variations in the 

 inherited actions of a partridge be preserved in like 

 manner, without any thought or conscious intention on 

 her part any more than on the part of the mullusc, the 

 hinge of whose shell has been modified and improved 

 independently of consciousness. Charles Darwin 

 Down, December 16, 1879 



NOTES 



We are much pleased to be able to announce that the Com- 

 mittee of the British Association for the Exploration of Socotra 

 have secured the services of Dr. I. B. Balfour, Professor of 

 Botany at Glasgow, as naturalist. Besides many other qualifica- 

 tions for the post Dr. Balfour has recently taken part in the 

 execution of a similar piece of work as one of the naturalists 

 attached to the station for die ob ervation of the Tram it of 

 Venus at Rodriguez. Dr. Balfour will leave for Aden oa the 

 9th inst., and proceed thence to Socotra. 



M. Terrier, the head of the French Survey, has been 

 appointed a Member of the Academy of Sciences. It may be 

 remembered that M. Perrier is a commander on the staff, and 

 has just accomplished one of the greatest geodetic feats on 

 record, the connection of the South of Spain with the Algerian 

 province of Oran. M. Perrier is a supporter of M. Koudaire's 

 scheme, and his appointment is considered likely to accelerate 

 the work of the survey for the great Saharan Railway. 



We are pleased to see that a movement is on foot to erect an 

 educational natural hi-tory museum in Perth, as a memorial to 

 the late Sir Thomas Moncrieffe, president of the Perth-hire Natu- 

 ral History Society. From a statement sent us by Dr. Buchanan 

 White, we notice that the organisers have a rational idea of 

 what such an institution should be, and their scheme is a c <m- 

 prehensive one, having in view the education of the citizens of 

 the ancient burgh, as well as the collection of objects of natural 

 history connected with the county. A generous citizen of Perth, 

 Mr. Robert 500/. of the 2,000/. which it is esti- 



mated, the building will cost. 



M. E. Levasseur, a well-known French geographer, has 

 invented an amusing an 1 instructive geographical game, to which 

 he gives the name of "Tourdu Monde." It is played on a 

 large terrestrial globe divided into 232 spherical rectangles, each 

 of which has a Dumber, corresponding to a number on a h.st, 



