The task of revising and bringing up to date a work which has been the guide, philosopher, and friend of thousands of commencing microscopists has been, in the present case, one of no small difficulty. On the one hand, there was the natural desire to interfere as little as possible with the original work; and on the other, the necessity of rendering available, to some extent at least, the enormous advance in every department which has taken place in the thirty-six years which have elapsed since the work was first offered to the public. The reviser has done his best not only to fulfil these two objects, but to keep in view the original purpose of the book.

In the popular department of pond-life especially, about fifty new illustrations have been added, mostly from the reviser’s own notebook sketches. The whole of the botanical part has been revised by one of our first English authorities, and, in short, no effort has been spared to make the work as accurate as its necessarily condensed form permits of. It is hoped, therefore, that it may be found not less useful than its predecessor by those for whom it is alone intended.