TYPICAL SPECTRA 36 Photo: Harvard College Observatory. A NEBULAR REGION SOUTH OF ZETA ORIONIS 37 Photo: Mount Wilson Observatory. STAR CLUSTER IN HERCULES 37 Photo: Astrophysical Observatory, Victoria, British Columbia. THE GREAT NEBULA IN ORION 40 Photo: Yerkes Observatory. GIANT SPIRAL NEBULA, MARCH 23, 1914 41 Photo: Lick Observatory. A SPIRAL NEBULA SEEN EDGE-ON 44 Photo: Mount Wilson Observatory. 100-INCH TELESCOPE, MOUNT WILSON 45 Photo: H. J. Shepstone. THE YERKES 40-INCH REFRACTOR 48 THE DOUBLE-SLIDE PLATE-HOLDER ON YERKES 40-INCH REFRACTING TELESCOPE 49 Photo: H. J. Shepstone. MODERN DIRECT-READING SPECTROSCOPE 49 By A. Hilger, Ltd. CHARLES DARWIN 56 Photo: Rischgitz Collection. LORD KELVIN 56 Photo: Rischgitz Collection. A GIANT SPIRAL NEBULA 57 Photo: Lick Observatory. METEORITE WHICH FELL NEAR SCARBOROUGH AND IS NOW TO BE SEEN IN THE NATURAL HISTORY MUSEUM 57 Photo: Natural History Museum. A LIMESTONE CANYON 60 Reproduced from the Smithsonian Report, 1915. GEOLOGICAL TREE OF ANIMALS 61 DIAGRAM OF AMOEBA 61 A PIECE OF A REEF-BUILDING CORAL, BUILT UP BY A LARGE COLONY OF SMALL SEA-ANEMONE-LIKE POLYPS, EACH OF WHICH FORMS FROM THE SALTS OF THE SEA A SKELETON OR SHELL OF LIME 64 From the Smithsonian Report, 1917. A GROUP OF CHALK-FORMING ANIMALS, OR FORAMINIFERA, EACH ABOUT THE SIZE OF A VERY SMALL PIN'S HEAD 65 Photo: J. J. Ward, F.E.S. A COMMON FORAMINIFER (POLYSTOMELLA) SHOWING THE SHELL IN THE CENTRE AND THE OUTFLOWING NETWORK OF LIVING MATTER, ALONG WHICH GRANULES ARE CONTINUALLY TRAVELLING, AND BY WHICH FOOD PARTICLES ARE ENTANGLED AND DRAWN IN 65 Reproduced by permission of the Natural History Museum (after Max Schultze). A PLANT-LIKE ANIMAL, OR ZOOPHYTE, CALLED OBELIA 68 Photo: J. J. Ward, F.E.S. TRYPANOSOMA GAMBIENSE 69 Reproduced by permission of _The Quart. Journ. Mic. Sci._ VOLVOX 69 PROTEROSPONGIA 69