I must put my fine English book back in its place, too;—but here, at last, comes a ‘work of light’ to help us, from my favourite pupil, who was out with me that day on the Downs, and nearly killed himself with keeping a fox in sight on foot, up and down them;—happily surviving, he has pursued the slower creature for me to its cave of silver earth; and writes thus. “I have sent you two little boxes—one containing common garden snail shells of various ages, and the other black striped Down shells; and you will see that in Box 1 the full-grown ones, with the strong finished lip, have four whorls each, and all the full-grown garden shells I have noticed had the same number, though they varied a little in size. The next largest in the box have only three and a half turns, but if they had lived longer they would have added on another half turn, bigger than all the rest of the shell put together. In fact, if one looks at this shell, one sees that any half whorl is half as large again as all the rest of the shell before it. Then, besides these, there are four or five younger shells, the smallest of which has only two and a half whorls, which exactly correspond to two and a half whorls taken from any of the larger shells; so I think we may conclude that a shell grows by adding on length only to the large end of a tapering tube, like a dunce’s cap, which, however, is curled up like a ram’s horn, to look prettier, take up less room, and allow the occupant to beat a retreat round the corner when a robin comes. By-the-bye, I wonder some birds don’t grow bills like corkscrews, to get at the snails with. “Then in box No. 2 there are several black striped Down shells, and the full-grown ones have six whorls, and the smallest ones, which died young, some four and some five, according to age; but the dunce’s cap is longer, and so there are more whorls. “I couldn’t get these facts clearly stated in two handbooks which I read. I suppose they took it for granted that one knew; but I found, what after all would lead one to infer the rest, that the young snail at birth corresponds to the colourless APEX of the shell, and that the colour only comes in that part which grows under the influence of light and air.” “Wednesday, Feb. 9. “Another fact is, that all the shells I ever remember looking at grow in the direction of the sun. “Another fact. Since the shells have been in this room, my chimneypiece has been full of sleepy, small, long-bodied spiders, which had gone to sleep for the winter in these black and white caverns, out of the reach of flocks of half-starved larks and starlings.”