CHAPTER IV--SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS Sir Norman Lockyer and Spectroscopic Studies of the Sun and Stars, p. 73--Observations made at South Kensington by Sir Norman and his staff, p. 74--His theories as to the influence of sun-spots and terrestrial weather, p. 75--Spectroscopic studies of sun-spots, p. 76--Studies of the so-called reverse lines of the spectrum, p. 78--Discovery of the new star in the constellation of Perseus, p. 80--Spectroscopic studies of the new star, p. 81--Professor Ramsay and the new gases, p. 82--University College in London, p. 83--Professor Ramsay's laboratory and its equipment, p. 84--The discovery of argon, p. 86--Professor Ramsay's work on krypton, neon, and zenon, p. 87--Discoveries of new constituents of the atmosphere, p. 88--Interesting questions raised by these discoveries, p. 89--Professor J. J. Thomson and the nature of electricity, p. 92--Study of gases in relation to the conduction of electricity, p. 93--Electricity regarded as a form of matter, p. 97--Radio-activity, p. 97--The nature of emanations from radio-active bodies, p. 10a--The source of energy of radioactivity, p. 106--Radio-activity and the structure of the atom, p. 108--Effect of radio-activity upon heat-giving life of the sun and the earth, p. 111. CHAPTER V--THE MARINE BIOLOGICAL LABORATORY The aquarium, p. 113--The arrangement of the tanks and exhibits, p. 114--The submarine effect of this arrangement, p. 115--Appearance of the submarine dwellers in their natural surroundings, p. 116--The eels and cuttle-fishes, p. 116--The octopuses, p. 117--The technical department of the laboratory, p. 119--The work of Dr. Anton Dohrn, founder of the laboratory, p. 121--The associates of Dr. Dohrn, p. 122--The collecting of surface specimens, p. 123--Collecting specimens by dredging, p. 124--Fauna of the Bay of Naples, p. 124--Abundance of the material for biological study, p. 125--Advantages offered by marine specimens for biological study, p. 126--Method of preserving jelly-fish and similar fragile creatures, p. 127--Uses made of the specimens in scientific study, p. 128--Different nationalities represented among the workers at the laboratory, p. 130--Methods of investigation, p. 131--Dr. Diesch's studies of heredity at the laboratory, p. 131--Other subjects under scientific investigation, p. 132--The study of chromosomes, p. 133--Professor Weismann's theory of heredity based on these studies, p. 33--Experiments in the division of egg-cells, p. 134--Experiments tending to refute Weismann's theory, p. 136--Dr. Dohrn*s theory of the type of the invertebrate ancestor, p. 137--Publications of the laboratory, p. 139--Meetings of the investigators at Signor Bifulco's, p. 141--Marine laboratories of other countries, p. 142. CHAPTER VI--ERNST HAECKEL AND THE NEW ZOOLOGY