622 



NA TURE 



[Oct. 23, 1884 



not a useless petal in the floral egg, not an unneeded line of 

 chasing in the decorated shell. It is shaped beautifully because 

 its shape is needed. In short, it is Nature's method ; the identi- 

 fication of beauty and use. But to resume. We may at this 

 point continue our illustrations of the analytical power of moderate 

 lenses by a beautiful instance. We are indebted to Albert 

 Michael of the Linnean Society of England for a masterly 

 treatise on a group of Acari, or Mites, known as the Oribatidcc. 

 Many of these lie has discovered. The one before you is a full 

 grown Nymph, of what is known as a palmicinctum. It is 

 deeply interesting as a form ; but for us its interest is that it 

 is minute, being only a millimetre in length. But it repeatedly 

 casts the dorsal skin of the abdomen. Each skin is bordered by 

 a row of exquisite scales ; and then successive rows of these 

 scales persist, forming a protection to the entire organism. Mark 

 then that we not only reveal the general form of the Nymph, but 

 the lens reveals the true structure of the scales, not enlargement 

 merely, but detail. The egg of the organism, still more mag- 

 nified, is also seen. 



To vary our examples -and still progress. We all know the 

 appearance and structure of chalk. The minute Foraminifera 

 have, by their accumulated tests, mainly built up its enormous 

 masses.^ But there is another chalk known as Barbadoes earth ; 

 it is siliceous, and is ultimately composed of minute and beauti- 

 ful skeletons such as those which, enormously magnified, you 

 now see. These were the glassy envelopes which protected 

 the living speck that dwelt within and built it. They are the 

 minutest of the Radiolaria, which peopled in inconceivable 

 multitudes the Tertiary oceans ; and, as they died, their minute 

 skeletons fell down in a continuous rain upon the ocean bed, 

 and became cemented into solid rock, which geologic action has 

 brought to the surface in Barbadoes, and many other parts 

 of the earth. If a piece of this earth, the size of a bean, be 

 boiled in dilute acid and washed, it will fall into powder, the 

 ultimate grains of which are such forms as these which you see. 

 The one before you is an instance of exquisite refinement of 

 detail. The form from which the drawing of the magnified 

 image was made was extremely small — a mere white speck in 

 the strongest light upon a black ground. But you observe it is 

 not a speck of form merely enlarged. It is not merely beauty 

 of outline made bigger. But there is— as in the delicate group 

 you now see— a perfect opening up of otherwise absolutely in- 

 visible details. We may strengthen this evidence in favour of 

 the analytical power of our higher lenses, by one more familiar 

 example, and then advance to the most striking illustration of 

 this power which our most perfect and powerful lenses can 

 afford. I fear that it may be taking too much for granted to 

 assume that every one in an audience like this has seen a human 

 flea ! Most, however, will have a dim recollection or suggestive 

 instinct as to its size in nature. Nothing striking is revealed by 

 this amount of magnification excepting the existence of breath- 

 ing pores, or spiracles along the scale armour of its body. But 

 there is a trace of structure in the terminal ring of the exo- 

 skeleton which we cannot clearly define, and of which we may 

 desire to know more. This can be done only by the use of far 

 higher powers. 



To effect this, we must carefully cut off this delicate structure, 

 and so prepare it that we may employ upon it the first of a 

 series of our highest powers. The result of that examination is 

 given here. 1 You see that the whole organ has a distinct form 

 and border, and that its carefully carved surface gives origin to 

 wheel-like areolae which form the bases of delicate hairs. The 

 function of this organ is really unknown. It is known from its 

 position as the pygidium ; and from the extreme sensitiveness of 

 the hairs to the slightest aerial movement may be a tactile organ 

 warning of the approach of enemies, the eyes have no power to 

 see. But we have not yet reached the ultimate accessible struc- 

 ture of this organ. If we place a portion of the surface under 

 one of the finest of our most powerful lenses, this will be the 

 result.'- Now, without discussing the real optical or anatomical 

 value of this result as it stands, what I desire to remind you of 

 is (1) the natural size of the Ilea ; (2) the increase of knowledge 

 gained by its general enlargement ; (3) the relation in size 

 between the flea and its pygidium ; and (4) the manner in which 

 our lenses reveal its structure, not merely amplify its form. Now 

 with these simple and yet needful preliminaries you will be 

 able to follow me in a careful study of the least, the very lowliest 



2 The pygidium of the flea, very highly magnified, was here shown. 

 «■« " ll!ustrae,on ° f thc Pygidium structure seen with i/ 35 th 



and smallest, of all living things. It lies on the very verge of our 

 present powers of optical aid, and what we know concerning it 

 will convince you that we are prepared with competent skill to 

 attack the problem of the life-histories of the smallest living 

 forms. The group to which the subject of our present study 

 belongs is the Bacteria. They are primarily staff-like organisms of 

 extreme minuteness, but may be straight, or bent, or curved, or 

 spiral, or twisted rods. This entire projection is drawn on glass, 

 with camera lucida, each object being magnified 2000 diams., 

 that is to say, four millions of times in area. Vet the entire 

 drawing is made upon an area of not quite three inches in 

 diameter and afterwards projected here. The objects therefore 

 are all equally magnified, and their relative sizes may be seen. 

 The giant of the series is known as Spirillum volutans ; and you 

 will see that the representative species given become less and 

 le»s in size until we reach the smallest of all the definite forms 

 and known to science as Bacterium termo. 



Now within given limits this organism varies in size, but if a 

 fair average be taken its size is such that 50,000,000 laid in order 

 would only fill the one-hundredth of a cubic inch. Now the 

 majority of these forms move with rapidity and grace in the fluids 

 they inhabit. But how? by what means? By looking at the 

 largest form of this group you will see that it is provided with two 

 delicate fibres, one at each end. Ehrenberg and others strongly 

 suspected their existence, and we were enabled, with more per- 

 fect lenses, to demonstrate their presence some twelve years ago. 

 They are actually the swimming organs of this Spirillum. The 

 fluid is lashed rhythmically by these fibres, and a spiral move- 

 ment of the utmost grace results. Then do the intermediate 

 forms that move also possess these flagella ? and does this least 

 form in nature, viz. Bacterium termo, accomplish its bounding and 

 rebounding movements in the same way ? Yes ! by a series of 

 resolute efforts, in using a new battery of lenses — the finest that 

 at that time had ever been put into the hands of man — I was 

 enabled to show in succession that each motile form of Bacterium 

 up to B. lineola accomplished its movements by fibres or flagella ; 

 and that in the act of self-division, constantly taking place, anew 

 fibre was drawn out for each half before separation. 

 (To be continued,) 



THE PERIPATETIC METHOD OF INSTRUC- 

 TION IN SCIENCE AND ITS DEVELOPMENT* 

 'PHE object of this paper is to plead for the introduction of 

 science as a part of the system of ordinary education in 

 all public elementary schools, and to describe the method by 

 which alone, in the opinion of the writer, it is possible that this 

 should be accomplished. There is a general consensus of opinion 

 that a far larger place than has hitherto been allowed in England 

 should be assigned to science in our national system of educa- 

 tion, as well as in our grammar-schools and Universities ; but 

 no strong conviction yet exists that a certain amount of strict 

 and definite scientific training should be given to all the scholars 

 in our public elementary schools as soon as they are prepared to 

 receive it, which is practically found to be after they have passed 

 the fourth standard. The extent of this claim for the introduc- 

 tion of science as a part of the ordinary curriculum of a public 

 elementary school must be noted, in order that the worth and 

 importance of the proposed method for securing thoroughly 

 effective teaching may be understood. 



The provision of special scholarships for those who possess 

 exceptional intellectual power — admirable and necessary as this 

 is — does not meet the broad claim I make. To furnish stages 

 in the ladder by which a lad of mark, endowed with "five 

 talents," may climb from the elementary school to the science 

 college, is only to offer to the children of the poor opportunities 

 to which they are justly entitled by virtue of the fact that genius, 

 like truth, can neither be bought or sold, and is bestowed upon 

 men entirely apart from any considerations connected with social 

 rank and circumstances. But scholars of average ability, those 

 who have no special endowments qualifying them for exceptional 

 careers, ought not to be kept in ignorance of the fixed laws and 

 the majestic marvels of the world in which they will have to 

 labour, or to be deprived of the practical guidance, the intellec- 

 tual interests, and the protection against coarse and degrading 

 tastes, which scientific training is capable of bestowing upon 



1 Paper read at the Social Science Congress, September 22, by Henry W. 

 Crosskey, 111'., Chairman of the School Management Committee of the 

 Birmingham School Baard. 



