The introduction of this deadly parasite to Europe was a mere chance, due to ignorance and stupid want of supervision of importations on the part of the Government, such as is common in this country, though less so in France and Germany—part of the blind mixing-up of the nicely adjusted products of all parts of the earth which civilised man is always bringing about with disastrous and terrifying results. In twenty years France lost 400 million pounds in consequence; three million acres of vineyards were destroyed. Other countries—Germany, Italy, and the Cape—also suffered. All sorts of remedies were suggested and tried, such as the application of poisons to the roots and the sinking of the vineyards under water. Gradually the only effective method of dealing with the case has been established. The old European vine-stocks or standards have been grubbed up in all but the very choicest vineyards, and American vines have been planted in their place. On to these have been grafted cuttings of the local French vines, and they have taken kindly to their new conditions. The produce of the French vineyards is now greater than it has ever been. It had fallen from an annual yield of 1,300,000,000 gallons to 650,000,000—but in 1900 it had risen again to a yield of more than 1,400,000,000 gallons. This history is a striking instance of the vast importance to civilised communities of a knowledge and control of even such minute living things as the plant-lice, and of the extraordinarily large results which obscure living things may produce. It must tend to convince reasonable men of the importance of accurate knowledge as to living things and of the necessity of expending public money in constantly improving and extending that knowledge. An ingenious illustration of the enormous fecundity of the plant-lice occurs to me as worth giving in conclusion. The late Professor Huxley—a careful and trustworthy authority—calculated that the produce of a single aphis would, in the course of ten generations, supposing all the individuals to survive, “contain more ponderable substance than five hundred millions of stout men; that is, more than the whole population of China.” And this calculation is held by some authorities to be below rather than above the mark! XXXVII CLOTHES MOTHS