ANNUAL OF SCIENTIFIC DISCOVERY. 



and animalcules, which start into existence as by magic, and in millions, we 

 have no difficulty in accepting the hypothesis of a universal diffusion of 

 germs eggs or seeds through the atmosphere. No matter where you 

 place organic substance in decay, if the air, in never so small a quantity, 

 can get at it, mould and animalcules will be produced. Close it in a phial, 

 seal the cork do\vn, take every precaution against admitting more air than 

 is contained between the cork and the surface of the water, and although 

 you may have ascertained that no plants or animalcules, no seeds or eggs, 

 were present when you corked the bottle, in the course of a little while, say 

 three weeks, on opening the bottle, you will find it abundantly peopled. To 

 explain this, and numerous other facts, the hypothesis of a universal diffu- 

 sion of germs through the air has been adopted; and the known fecundity 

 of plants and animalcules suffices to warrant the belief that millions of mil- 

 lions of germs may be constantly floating through the air. Ehrcnburg 

 computes the rate of possible increase of a single infusory, Paramednm, at 

 two hundred and sixty-eight millions a month. And it is calculated that 

 the plant named Bovista gigantum will produce four thousand millions of 

 cells in one hour. As the mould plants are single cells, and as they multiply 

 by spontaneous division, the rapidity with which they multiply is incal- 

 culable. 



From all this, you see how naturally the idea of universal diffusion of 

 germs has become an accepted fact. If it is a fact, we must feel not a little 

 astonished at finding the dust we examine so very abundant in starch, coal, 

 silica, chalk, rust, hair, scales, and even live animals, and so strangely defi- 

 cient in this germ-dust. The germs are said to be everywhere; millions upon 

 millions must be diffused through the air; every inch of surface" must be 

 crowded with them. Do we find them? "We find occasional pollen grains 

 and seeds. But we find no animalcule eggs, and no animals, except the 

 Rotifers and Tardigrades. ~\Ye find almost everything but eggs. "O," 

 you will perhaps remark, "that is by no means surprising; if they are dif- 

 fused in such enormous quantities through the air, it stands to reason that 

 they must be excessively minute, otherwise they would darken the air; and, 

 if they are excessively minute, they escape your detective microscope, that 's 

 all." Your remark has great plausibility; indeed, it would have overwhelm- 

 ing force, were there not one fatal objection to the assumption on which it 

 proceeds. If the eggs of animalcules ivere so excessively minute as you 

 imagine them to be, there would be no chance of our detecting them. But 

 it happens that the size of the eggs of those animalcules which are known 

 (and of many we are utterly ignorant) is, comparatively speaking, consider- 

 able; at any rate, the eggs, both from size and aspect, are perfectly recog- 

 nizable inside the animalcule; and, if we can distinguish these eggs when the 

 parent is before us, or when we have crushed them out of her body, it will 

 be difficult to suppose that we could not distinguish them among the other 

 objects in a pinch of dust, when a drop of water has been added. 



ZOOLOGICAL SUMMARY. 



Domestication of the Canna in England. The Canna (Oreas Canna), a. South 

 African ruminant, and largest of the antelope species, approaches the ox in 

 form and weight, multiplies its kiurl in captivity, grows rapidly, fattens 

 easily, lias a fine-drained and juicy flesh, and there is reason to believe that 

 it may be extensively raised for the market. The present stock in England 



