Jan. 2, 1890] 



NATURE 



199 



in its period and the much larger change observed in the period 

 of another variable of the same class in Cygnus becomes 

 important. Besides the possibility of a third disturbing body it 

 may be remarked that the existence of the solar corona and 

 perhaps other appendages of the sun suggests that a resisting 

 medium may exist in the entire space traversed by Algol and its 

 satellite at each revolution. Also if the influence of gravitation 

 is propagated in time (with whatever degree of velocity) the very 

 rapid angular motion of a satellite which performs a complete 

 revolution in less than three days (and in another variable of 

 this class in twenty hours) could hardly fail to exhibit traces 

 of this time-propagation. The attractive force, in fact, 

 would never act in the line joining the centres of the principal 

 star and satellite, and the deviation would probably be per- 

 ceptible. I hope some mathematical astronomer will take up 

 the problem, and show what the effects of each of these supposed 

 causes would be. W. H. S. Monck, 



16 Earlsfort Terrace, Dublin, December 21, 1889. 



Maltese Butterflies. 



In reading Mr. Wallace's "Darwinism" I am reminded by 

 his observations on Island fauna (p. 106) of the impressions 

 made upon me by the natural productions of Malta. My time 

 was so fully occupied that I had little opportunity of exploring 

 the country districts. I paid one visit to the extraordinary ruins 

 of a Phoenician temple at Hagiar Kim, and one to the curious 

 islet in St. Paul's Bay. On the latter I noticed several strange 

 thistles and a beautiful flower — something like a large pink or 

 purplish Tutsan. On the barren wastes round Hagiar Kim 

 many familiar wild flowers grew, but all seemed shrunk and 

 shrivelled as compared with those of Britain. The only un- 

 familiar one was called by the natives "the English flower." It 

 was a tall trefoil with a drooping yellow trumpet-flower (not at 

 all papilionaceous in form), and grew plentifully by the edges of 

 the dustiest roads — unlike anything I know in England. 



I lived for some time at the Imperial Hotel, at Sliema, which 

 has a somewhat extensive garden, in which I used to spend about 

 half an hour every morning. During April and May it was very 

 lovely. The oleanders were then in their richest bloom ; a 

 shrub like a gigantic heliotrope, both in flower and leaf, was 

 frequented by myriads of humming-bird moths ; there were a 

 few strawberry-plants, the fruit of which was delicious, although 

 even smaller than that of our own wild kind ; but most attractive 

 to me were the clumps of valerian and scabious which were 

 haunted, just as at home, by crowds of butterflies. These in- 

 cluded blues, coppers, wood-ladies, painted-ladies, red-admirals, 

 tortoise-shells, and swallow-tails. All of these were smaller 

 than their English relatives are, and much less brilliant in colour. 

 The swallow-tails were especially dwarfed in their proportions, 

 I am puzzled to account for their presence in Malta, as there is 

 nothing like a marsh or a fen in the whole island, whilst in 

 England they are only to be found in the district of the meres. 

 Can any of your readers throw light on this mystery ? I saw 

 several of the larger hawk- moths. They did not seem to suffer 

 in size, but even they were dimmer in their colours. 



Hoping to get a general idea of Maltese entomology, I visited 

 the University Museum — only to find a few cases of insects in 

 which every specimen had been devoured by mites ! 



George Eraser. 



Leighside, Tunbridge Wells, December 22, 1889. 



A Preservative, 



I HAVE been very much troubled in conducting classes in 

 mammalian anatomy by the want of a preservative medium 

 which would retain the natural colour and texture of tissues, 

 would impart to them no offensive smell, would be inexpensive, 

 and easily handled. Various experiments with freezing, alco- 

 holic, glycerine, and other media have all proven failures, and 

 this fall I turned to experimentation upon the simplest and 

 cheapest of all chemical reagents— water and table-salt. My 

 entire success with these was so satisfactory that I shall, at the 

 risk of telling an old story, state the experiments here. 



I tried preserving squirrels in three strengths of salt solution, 

 one of 5 parts by weight of salt to 95 of water, a second of 

 10 per cent, salt, and a third of 15 per cent. All gave satisfac- 

 tion, but the 10 per cent, seems best, because the weakest 

 solution in which putrefaction could not take place. Specimens 



placed in five times their bulk of this solution retain the natural 

 flexibility of all the tissues ; the peculiar look of nerve-tendon 

 and blood-vessel against muscle is retained ; the tint of muscle 

 is faded somewhat by the solution of haemoglobin from the blood, 

 but it is still distinctly reddish ; there is no putrefactive odour ; 

 all of this after four weeks standing in the laboratory. 



This is so simple a preservative that I wonder that it is not 

 in common use. H. Leslie Osborn. 



Hamline University, St, Paul, Minnesota, 

 December 7, 1889. 



The Evolution of Sex. 



It is a fact well known to pigeon fanciers that the two eggs laid 

 by pigeons almost invariably produce male and female. But no 

 attempt appears to have been made to ascertain which of the 

 two eggs produces the male, and which the female. The second 

 egg is laid about twenty-four hours after the first. I have kept 

 pigeons for seven or eight years, and have only met with one or 

 two instances of the young birds, produced from the two eggs, 

 being of the same sex, Recently I have made several experi- 

 ments to ascertain if any relation exists between the order in 

 which the eggs are laid and the sexes of the young birds 

 produced. The results show that the egg first laid produces the 

 female, the second egg the male. It may, perhaps, be well to 

 give the experiments. 



(i) Egg I of pair A produced a female ; egg 2 was bad. 

 ('') Egg I. of pair B produced a female ; egg 2 a male. 

 (iii) Egg I of pair B produced a female ; egg 2 a male, 

 (iv) Egg 2 of pair B produced a male ; egg i was bad. 

 (^) Egg I of pair C produced a female ; egg 2 was bad, 

 (vi) Egg 2 of pair D produced a male ; egg I was broken. 



These experiments were made on white fantail shakers. A 

 large number of experiments must be made to prove if this 

 relation does exist ; should it be found correct, an examination 

 of the eggs and of the ovary of the parent might throw some 

 light upon the "evolution of sex." M. S. Pembrey. 



Oxford, December 14, 1889. 



Fighting for the Belt. 



A FIGHT has been going on in my verandah for the last half- 

 hour between two young birds — minas — with four birds of last 

 season looking on. 



Now the fight is just over. I have watched it throughout, and 

 am positive that one of the on-lookers walked often round the com- 

 batants without interfering ; and that another on-looker came, 

 when he (or she?) could, and attacked one of the fighters. I say 

 " came when he could," because the other on-looker prevented 

 him if possible — even fighting to that end. It seemed to me 

 very much as if two youngsters from different nests were fighting 

 for the belt, and the parents looking on— the one complacently at 

 her offspring's success, the other angry and breaking the rules of 

 the ring to help the weaker. F. C. Constable. 



Karachi, December i, 1889. 



The British Museum Reading-Room. 



The proper ventilation of this spacious room is a problem, 

 surely not insoluble, but still awaiting solution. Is it not a 

 serious grievance that to make use of one of the finest libraries in 

 existence, means, for many, injury to health ? Bad headaches 

 and other ills, due to the stuffy and impure atmosphere which 

 collects about the desks, are a common experience ; and I know 

 men who have given up going to the place on that account. 

 For readers who live by work which can only be done there 

 (some of whom are women), the matter is especially grave. 

 Officials, again, will tell you that they often feel thoroughly done 

 out after their day's work, which in itself is not generally severe. 

 It seems to me the atmosphere improves after the lamps are lit ; 

 possibly owing to the upward current of heated air. If this were 

 verified, it might offer a clue to improvement. The whole 

 matter calls for thorough scientific investigation ; and I would 

 suggest, as a preliminary step, that analysis be made of the air 

 (say) on a Saturday afternoon, with regard not only to its gaseous 

 constituents, but also to micro-organisms, which are no doubt 

 olentiful. A, B, M, 



