tedious and uncertain, and it was almost impossible to cut a piece of tissue into a series of thin slices without losing or destroying considerable portions. Microtomes, with various accessory mechanical appliances, have now been invented, and by means of these not only are slices of great tenuity made with ease, but there is little difficulty in cutting the most delicate organism into a ribbon of consecutive slices. Such new methods have made almost a revolution in the study of zoölogy, particularly of the lower forms of life and of the embryonic stages of higher animals, and books written before these methods became common have naturally been superseded. Huxley did far more for the teaching of science than the preparation of books, however useful these were. He was the practical inventor of the laboratory system of teaching zoölogical science, and all over the world the methods invented by him have been adopted in university laboratories and technical schools. He had always declared that since zoölogy was a physical science, the method of studying it must needs be analogous to that which is followed in other physical sciences. If a man wishes to be a chemist, it is necessary not only that he should read chemical books and attend chemical lectures, but that he should actually perform the fundamental experiments in the laboratory for himself, and thus learn exactly what the words which he reads in his books and hears from his teachers, mean. "If you want a man to be a tea-merchant, you don't tell him to read books about China or about tea, but you put him into a tea-merchant's office where he has the handling, the smelling, and the tasting of tea. Without the sort of knowledge which can be gained only in this practical way, his exploits as a tea-merchant will soon come to a bankrupt termination." The great and obvious difficulty in the practical teaching of biology appeared to be the immense number of different kinds of animals and plants in existence. A human life would not suffice for the examination of a hundredth part of these. Huxley met the difficulty by the "type" system. "There are certainly more than 100,000 species of insects, and yet anyone who knows one insect, if a properly chosen one, will be able to have a fair conception of the structure of the whole. I do not mean to say he will know that structure thoroughly, or as well as is desirable that he should know it; but he will have enough real knowledge to enable him to understand what he reads, to have genuine images in his mind of these structures which become so variously modified in all the forms of insects he has not seen. In fact, there are such things as types of form among animals and vegetables, and for the purpose of getting a definite knowledge of what constitutes the leading modifications of animal and plant life, it is not needful to examine more than a comparatively small number of animals and plants."