The change which is produced in excrement when mixed with earth whereby the excrement is humified—_i.e._, changed to something which is indistinguishable by our senses from ordinary garden mould, or humus, is due to the action of fungoid organisms. Some of these belong to the 'mould' fungi, such as penicillium and saccharomyces, while others are allied to the schizomycetes, otherwise known as bacteria, bacilli, and micrococci. A very important organism, or class of organisms, in this connection are those which bring about the nitrification of nitrogenous matters, whereby they are oxidised and made soluble, so as to be readily absorbed by the roots of growing plants. I prefer, however, to use the word _humification_ in place of nitrification, because it is not likely that nitrification is the sole change which takes place, and it is at least highly probable that many of the fungi which grow in nitrogenous matter play a very important part in producing fertility and in feeding higher plants. The intestines of animals swarm with bacteria and allied bodies, and it may be assumed, in the absence of evidence to the contrary, that excrements carry with them, so to say, in the form of moulds and bacteria, bodies which help in their subsequent humification. Which of us has not noticed the excrement of a dog, evenly covered with exquisitely graceful stalks of fungus as with a crop of erect white hairs. The greatest of all human observers must have seen this, for he makes the Queen say to Hamlet: 'Your bedded hair, like life in excrements, Starts up and stands on end.' Ordinary humus contains such organisms in countless numbers, and it is probable that when excreta are mixed with sterile bodies, such as ashes, the necessary organisms are in part supplied by the excreta themselves, or possibly gain access from the air around. In order that humification may take place two things are necessary:— 1. The matter must be tolerably dry—absolute dryness checks the process, so does excess of moisture. It is stated that about 33 per cent. of moisture is the amount with which the humifying change is most rapid. 2. The access of air is necessary, because the organisms which produce humification are aërobic, and, as much of the change consists of oxidation, it is evident that the free access of air is essential. ACTUAL PRACTICE It may be well to refer here to what is actually done in my garden at Andover, in Hampshire. It should be stated that the garden is close to the centre of the town of Andover, the chief town in West Hants (a purely agricultural district), with about 6,000 inhabitants. The garden abuts on a street and lies very low, being only two or three feet at most above the average level of the river Anton, which forms one of its boundaries.