It may be well here to verify the quotations, and also to consult Darwin’s _Naturalist’s Voyage_, to ascertain what kind of objects he examined with the simple appliances at his command. In the first chapter there is an interesting account of a curious limy deposit on the rocks of the island of St. Paul’s, and of the discoloration by confervae of the water, which, ‘under a weak lens, seemed as if covered by chopped bits of hay, with their ends jagged.’ Then we have an account of the confervae in the Indian Ocean, and of infusoria so numerous as to tinge the water off the coast of Chile. In the second chapter we have observations and experiments on planarian worms. ‘Having cut one of them transversely into two nearly equal parts, in the course of a fortnight both had the shape of perfect animals.’ In the next chapter he records some observations on the structure of vitrified tubes formed by lightning striking loose sand. In the fifth chapter is an elaborate description of a kind of sea-pen; and in the ninth chapter there are some remarks on the vast number of eggs in the egg-ribbon of a sea-slug, and on the ‘bird’s-head’ organs in certain Polyzoa. These remarks were, of course, founded on actual inspection with the simple microscope. To this instrument, also, we owe the discovery of the tadpole-like larvae of Ascidians, or Tunicates, as they are now generally called. ‘At the Falkland Islands I had the satisfaction of seeing, in April, 1833, and therefore some years before any other naturalist, the locomotive larvae of a compound ascidian.... The tail was about five times as long as the oblong head, and terminated in a very fine filament. It was, as sketched by me under a simple microscope, plainly divided by transverse opaque partitions, which I presume represent the great cells figured by Kovalevsky. At an early stage of development the tail was closely coiled round the head of the larva[1].’ * * * * * We come now to our pocket lens, which may be purchased for a few shillings of any optician. One can buy a serviceable single lens, in an ebonite handle, for a shilling; and this cheap instrument is sufficiently powerful not only to give the worker a good general idea of the form and structure of objects, but to enable him to do real work. With it the habits of many of the inmates of his aquaria may conveniently be watched; he may see their development from stage to stage of their life-history; and with it, when they are broken up, he may make out a good deal of their external and internal anatomy. [Illustration: FIG. 1.--Hand Magnifier and Stand.]