July 0, 1883. 



o KNOWLEDGE ♦ 



AH ti.0S^^T try 



. ^MAGi^ZlNEOF^ENCE 



PlAIKlXfORHED -EXACTLfDESCRIBED 



LONDON: FRIDAY, JULY 6, 1883. 



Contents op No. 88. 



PAGE 

 A Naturalist's Year. XVI. About 



Variatiou. ByGrant Allen 1 



The Chemistry of Cookery. XIII. 



By W. Mattieu WiUiama 2 



Geolojjy and A^jriculture. By J. 



Vincent Elsdeti, F.C.S., &c 4 



Laws of BriRhtness. (/«/«.) By 



M. A. Proctor 5 



The Amateur Electrician 6 



Savage and Anthropolofiist 7 



The Fisheries Exhibition. (/«««). 



By John Ernest Ady 8 



PAGB 



Thousbt-Headinj; 



Flight of a Vertical Missile. By 



H. A. Proctor '.. lu 



God's Will n 



Editorial Gossip 11 



The Face of the Sky l:! 



Correspondence: Rational Dress — 

 Genealogical Puzzle — Letters Re- 

 ceived and Short Answers U 



Our Mathematical Column 14 



Our ■RTiist Column 1.5 



Our Chess Column 16 



A NATURALIST'S YEAR. 



.r 



By Grant Allen. 

 XVI.— ABOUT VARIATION. 



STROLLING along the lane by the mill-stream this 

 afternoon, I see with a shudder that the epilobes and 

 the St. John's worts are coming out in blossom again for 

 the season, and I feel dimly conscious in my own heart 

 tliat the annual task of trying to sort them out decently 

 into well-marked divisions will recur once more in full 

 tediousness. They are a hopeless set of interlacing species, 

 these weedy, wayside summer flowers ; a perfect chaos of 

 gradually-merging characteiistics, eacli supposed kind 

 shading off imperceptibly into the next through infini- 

 tesimal and imperceptible gradations. Of course, I am 

 personally quite convinced that the effort to introduce an 

 artificial separation where Nature still keeps up an un- 

 broken series is really as aVisurd as it is futile : but the 

 superstitions of the systematists die hard, and I feel in 

 duty bound to settle in my ov;n mind tu which particular 

 bundle of his arbitrary groups a conscientious technical 

 botanist would consider himself at liberty to refer this, 

 that, or the other particular epilobe, or hypericum, or 

 hawkwecd. The thing doesn't really matter in the least, 

 being only a question of human naming, not a question of 

 genuine natural distinctness ; but if one leaves it undone, 

 one has an unpleasant sense of a social duty unperformed, 

 and an important dogma in the Athanasian creed of con- 

 servative science imperfectly understood. 



It is in great part the general want of knowledge as to 

 the clost! way in which uiany large groups of species thus 

 interosculato that makes most people hesitate so much 

 about accepting the simple truths of evolutionism. The 

 animals with which they arc best acquainted — und most 

 people look at the matter from the standpoint of animal 

 lift! alone — are a few big mammals, all readily distinguish- 

 able from one another, at least here and now, and with 

 few remaining intermediate links to bridge over the gaps 

 between them. Nobody is in any danger of mistaking a 

 cow for a sheep, or even a horse for a donkey ; and the 

 various tarpans, and onagers, and quaggas, and zebras, 

 which span the gulf in the last instance and do really 



merge into one another very indefinitely, are only to be 

 seen in the Zoological Gardens, or else in Tartary, Central 

 Africa, and other reasonably inaccessible parts. But when 

 we come to examine all the known species of any gieat 

 group, especially among plants, the real difficulty is often 

 not to find intermediate links, but to discover any well 

 demarcated lines of division, or any constant assemblage of 

 characters marking tlieartificial bundlesinto which we choose 

 to distribute them. Our English flora is a small and frag- 

 mentary one, so that this difficulty is not felt within its 

 narrow limits so greatly as when we examine wider areas ; 

 but whenever one comes to compare together a large 

 number of specimens from all parts of the world, it is 

 wonderful how extremely elusive is the task of species- 

 making. True species do often undoubtedly exist : that is 

 to say, there are certainly many groups in which the 

 various existing individuals fall naturally into well-marked 

 divisions, all the intervening types having been killed out 

 by the competition of the better-adapted specific forms, as 

 Mr. Darwin has pointed out. Still, many other groups, 

 perhaps almost as numerous (among plants, at least), do 

 also exist, in which there is no such distinct demarcation 

 of species : the various typical forms merge on either side 

 into one another by every possible intermediate variation. 

 Perhaps these are instances of species in the making ; 

 perhaps they show us that primitive plastic state during 

 which variations have not yet become fixed and definite ; 

 but, in any case, there they are, and even the most rigo- 

 rously orthodox botanists can hardly deny their existence. 

 The local British interest of the epilobes, the St. John's 

 worts and the liawkweeds, consists in the fact that they 

 display just this close interosculation of species even within 

 the range of our own narrow English flora. On the one 

 hand, nobody could fail to recognise the difference between 

 some of the most distinct types — for example, the great 

 purple willow herb, or the pretty pink rose-bay, as com- 

 pared with the hoary epilobe and the square epilobe of our 

 wayside ditches ; or again, the great St. .John's wort of our 

 gardens, bearing flowers three or four inches in diameter, 

 as compared with the scrubby, small-flowered Jli/jH-ricum 

 duhiuin and Hyiirricuiii qundnuigulnm, that line our dusty 

 country roads. But, on the other hand, if one attempts to 

 divide them all up into distinct species, one finds oneself 

 hampered by all kinds of intermediates, which make the 

 definite classification of the text-books practically im- 

 possible in actual practice. Indeed, the text-l)Ooks them- 

 selves all difl't-r as to the number of species they 

 admit ; and though some botanists will at once decide off- 

 hand by what name they would call a particular specimen, 

 there are other wiser and more cautious authorities who 

 will not thus commit themselves to a fixed and dogmatic 

 nomenclature. I turn to Dr. Bentham on these very 

 epilobes, and I find he truly remarks : " The numerous 

 forms the species assume in every variety of climate make 

 it exceedingly difficult to define them upon any certain 

 principle, and botanists seldom agree as to the number 

 they should admit. Those here adopted are the most 

 marked among our British forms : but it must be con- 

 fessed that in some instances intermediates are to be met 

 with which will be found very puzzling." He then goes 

 on to say that in all cases the style should be carefully 

 observed when fresh, in order to see whether it is 

 entire or four-lobed ; but even this distinction, upon 

 which he bases his table of species, is a very unim- 

 portant one ; for in most epilobes the four lobes of the 

 style are joined in a club-shaped head at an earlj' stage in 

 the bud, and only open as tlie flower matures ; while 

 even in those species where tliey never open, the marks 

 of the four cohering lobes may be easily seen with 



