Oct. 23, 1884] 



NA TURE 



621 



microscope, and, with a lens just competent to reveal the minutest 

 objects, examined. The field of view presented is seen in Fig. 1, 

 A. But — with the exception of the dense masses which are known 

 as zooglcea or bacteria, fused together in living glue— the whole 

 field was teeming with action. Each minute organism gyrating 

 in its own path, and darting at every visible point. The same fluid 

 waJ now left for sixteen hours, and once more a minute drop was 

 taken and examined with the same lens as before. The field pre- 

 sented to the eye is depicted in Fig. 1, B, where it is visible that 

 whilst the original organism persists yet a new organism has arisen 

 in and invaded the fluid. It is a relatively long and beautiful spiral 

 form, and now the movement in the field is entrancing. The 

 original organism darts with its vigour and grace, and rebounds 

 in all directions. But the spiral forms revolving on their axes 

 glide like a flight of swallows over the ample area of their little 

 sea. Ten hours more elapsed and, without change of circum- 

 stances, another drop was taken from the now palpably putrescent 

 fluid. The result of examination is given in Fig. 1, c, where it 

 will be seen that the first organism is still abunJant, the spiral 

 organism is still present and active, but a new and oval form, 

 not a bacterium, but a monad, has appeared. And now the 

 intensity of action and beauty of movement throughout the field 

 utterly defy description, gyrating, darting, spinning, wheeling, 

 rebounding with the swiftness of the grayling and the beaut) of 

 the bird. Finally, at the end of another eight to sixteen hours, 

 a final " dip " was taken from the fluid, and under the same lens 

 it presented as a field what is seen in Fig. I, D, where the largest 

 of the putrefactive organisms has appeared and has even more 

 intense and more varied movements than the others. Now the 

 question before us is, "How did these organisms arise ? " The 

 water was pure ; they were not discoverable in the fresh muscle 

 of fish. Yet in a dozen hours the vessel of water is peopled with 

 hosts of individual forms which no mathematics could number ! 

 How did they arise ? from universally diffused eggs ? or from the 

 direct physical change of dead matter into living forms ? Twelve 

 years ago the life-histories of these forms were unknown. We 

 did not know biologically how they developed. And yet 

 with this great deficiency it was considered by ^ine that their 

 mode of origin could be determined by heat experiments on the 

 adult forms. Roughly the method was this. It was assumed 

 that nothing vital could resist the boiling point of water. Fluids, 

 then, containing full-grown organisms in enormous multitudes, 

 chiefly bacteria, were placed in flasks, and boiled for from five to 

 ten minutes. While they were boiling the necks of the flask-; were 

 hermetically closed; and the flask was allowed to remain unopened 

 for various periods. The reasoning was : " Boiling has killed all 

 forms of vitality in the flask ; by the hermetical sealing nothing 

 living can gain subsequent access to the fluid ; therefore, if living 

 organisms do appear when the flask is opened, they must have 

 arisen in the dead matter de novo by spontaneous generation, 

 but if they do never so arise the probability is that they originate 

 in spores or eggs." 



Now it must be observed concerning this method of inquiry 

 that it could never be final : it is incompetent by deficiency. 

 Its results could never be exhaustive until the life-histories of 

 the organisms involved were known. And further : although 

 it is a legitimate method of research for partial results, and was 

 of necessity employed, yet it requires precise and accurate 

 manipulation. A thousand possible errors surround it. It can 

 only yield scientific results in the hands of a master in physical 

 experiment. And we find that when it has secured the requisite 

 skill, as in the hands of Prof. Tyndall, for example, the result 

 has been the irresistible deduction that living things have never 

 been seen to originate in not-living matter. Then the ground 

 is cleared for the strictly biological inquiry, How do they 

 originate? To answer that question we must study the life- 

 histories of the minutest forms with the same continuity and 

 thoroughness with which we study the development of a cray- 

 fish or a butterfly. The difficulty in the way of this is the 

 extreme minuteness of the organisms. We require powerful and 

 perfect lenses for the work. Happily during the last fifteen 

 years the improvement in the structure of the most powerful 

 lenses has been great indeed. Prior to this time there were 

 English lenses that amplifi-d enormously. But an enlargement 

 of the image of an object avails nothing, if there be no con- 

 current disclosure of detail. Little is gained by expanding the 

 image of an object from the ten-thousandth of an inch to an inch, 

 if there be not an equivalent revelation of hidden details. It 

 is in this revealing quality, which I shall call Magnification as 

 distinct from amplification, that our recent lenses so brilliantly 



excel. It is not easy to convey to those unfamiliar with objects 

 of extreme minuteness a correct idea of what this power is. 

 But at the risk of extreme simplicity, and to make the higher 

 reaches of my subject intelligible to all, I would fain make this 

 plain. 



But to do so I must begin with familiar objects, objects used 

 solely to convey good relative ideas of minute dimension. I 

 begin with small objects with the actual size of which you are 

 familiar. All of us have taken a naked-eye view of the sting of 

 the wasp or honey-bee ; we have a due conception of its size. 

 This is the scabbard or sheath, which the naked eye sees. 1 Within 

 this are two blades, terminating in barbed points. The point of 

 the scabbard more highly magnified is presented, showing the 

 inclosed barbs. One of the barbs, looked at on the barbed 

 edge, is also seen. Now these two barbed stings are tubes, 

 with an opening in the end of the barb. Each is connected with 

 the tube of the sac C. This is a reservoir of poison, and D is 

 the gland by which it is secreted. Now I present this to you, 

 not for its own sake, but simply for the comparison, a com- 

 parison which struck the earliest microscopists. Here is the 

 scabbard carefully rendered. One of the stings is protruded 

 below its point, as in the act of stinging : the other is free 

 to show its form. Now the actual length of this scabbard in 

 nature was the one-thirtieth of an inch. I have taken the point 

 C of a fine cambric sewing needle, and broken it off to slightly 

 less than the one-thirtieth of an inch, and magnified it as the 

 sting is magnified. Now here we obtain an instance of what I 

 mean by magnification. The needle-point is not merely bigger, 

 unsuspected details start into view. The sting is not simply 

 enlarged, but all its structure is revealed. Nor can we fail to 

 note that the finish of art differs from that of Nature. The 

 homogeneous gloss of the needle disappears under the fierce 

 scrutiny of the lens, and its delicate point becomes furrowed and 

 riven. But Nature's finish reveals no flaw, it remains perfect to 

 the last. 



We may readily amplify this. The butterflies and moths of 

 our native lands we all know ; most of us have seen their minute 

 eggs. Many are quite visible to the unaided eye ; others are 

 extremely minute. A gives the egg of the Small White Butterfly, 2 

 E that of the Small Tortoiseshell, c that of the Waved Umber 

 Moth, D that of the Thorn Moth, E that of the Shark Moth, 

 at F we have the delicate egg of the Small Emerald Butterfly, 

 and at G an American Skipper, and finally at H the egg of a 

 moth known as Mania Maura. In all this you see a delicacy of 

 symmetry, structure and carving, not accessible to the eye, but 

 clearly unfolded. We may, from our general knowledge, form 

 a correct notion of the average relation in size existing between 

 butterflies and their eggs ; so that we can compare. Now there 

 is a group of extremely minute insect-like forms that are the 

 parasites of birds. Many of ihem are just plainly visible to the 

 naked eye, others are too minute to be clearly seen, and others 

 yet again wholly elude the unaided sight. The e Epizoa generally 

 lodge themselves in various parts of the plumage of birds ; and 

 almost every group of birds becomes the host of some specific or 

 varietal form with distinct adaptations. There is here seen a 

 parasite that secretes itself in the inner feathers of the peacock, 

 this is a form that attacks the jay, and here is one that secretes 

 itself beneath the plumage of the partridge. 



Now these minute creatures also deposit eggs. They are placed 

 with wonderful instinct in the part of the plumage and the part 

 of the feather which will most conserve their safety ; and they 

 are either glued or fixed by their shape or by their spine m the 

 position in which they shall be hatched. I show here a 

 group of the eggs of these minute creatures. I need not call 

 your attention to their beauty ; it is palpable. But I am fain to 

 show you that, subtle and refined as that beauty is, it is clearly 

 brought out. The flower-like beauty of the egg of the pea- 

 cock's parasite, the delicate symmetry and subtle carving of 

 the others simply entrance an observer. Note then that it 

 is not merely enlarged specks of form that we are beholding, 

 but such true magnifications of the objects as bring out all 

 their subtlest details. And it is this quality that must charac- 

 terise our most powerful lenses. I am almost compelled to note 

 in passing that the beauty of these delicate and minute objects 

 must not be considered an end— a purpose— in Nature. It is not 

 so. The form is what it is because it must be so to serve the end 

 for which the egg is formed. There is not a superfluous spine„ 



1 A magnified Image of the bee's sting was projected on the screen. 



= A series of the eggs of butterflies were then shown, as were the objects 

 successively referred 10 but not here reproduced. 



