So that ichneumon and starling are friends to the Rose, whilst the other insect, the spider, and the owl are enemies. Yet both the starling and the spider are probably, almost certainly on the whole, friends of the Rose, although they are unfriendly in this special case. With all other similar series or changes the final term is either a bird or animal of prey or mankind. Until we introduce the idea of man as the culminating point of the series, the whole of it seems to be without any special meaning or advantage. But when we think of how man utilizes the work of plants and animals, then the whole scheme becomes intelligible and complete; it is like a well-rounded story with a worthy and adequate end. Moreover, what man has done so far is only an instalment of what he will probably succeed in doing. All who have brought up caterpillars or bees know that their greatest difficulty arises from certain minute insects or fungus enemies. We already know enough about these latter to fight them with some chance of success, but there are hundreds of other spores and germs floating in the atmosphere, and coming to rest on animals, on clothing, or on the leaves or petals of plants. These germs are now just as wild as, and infinitely more dangerous than the furious aurochs, the disdainful wild asses, or the ferocious wolves that our forefathers succeeded in domesticating. Those bacteria, or germs, for instance, which are only one-thousandth of a millimetre long, are only visible by the help of a microscope. A row of three hundred thousand of them would be required to make an inch in length! Yet one of these germs can be mature and divide into two new germs in twenty minutes. In forty minutes there would be four, in an hour eight, and so on. The number after twenty-four hours is almost incredible. These little germs stick to our clothes, fingers, lips, money, newspapers, and anything that is often handled. They hover in the air we breathe, permeate the food we eat, and inhabit water, and especially milk, in enormous numbers. Some of them are deadly. One might easily decimate a whole population, as indeed happened in the South Sea Islands when smallpox was introduced. Others are harmless and even necessary. But to-day if you go into a bacteriological laboratory you will find hundreds and thousands of little glass tubes all neatly labelled and stoppered with cotton wool. If you read those labels you will see that the bacteria of all sorts of horrible and loathsome diseases have been captured and imprisoned. There is the deadly anthrax bacillus peacefully discolouring gelatine; in another, possibly the germs of hydrophobia may be undergoing a process of taming or treatment.