The book discusses reservoir sites and the use of the microscope and photomicrography. The latter part of the book, which describes various groups of water organisms, has been revised. The plates showing common water organisms have been printed in color, making identification easier. The book is recommended for use in bacteriological and public health laboratories and in the office of the water engineer. John W. Evans criticizes the use of "micromicron" in a translation of Nikitin's work, arguing that it should be "micromillimetre." He explains that "micromicron" would mean a millionth of a micron, a unit useful for expressing intermolecular distances. Newton B. Pierce discusses the origin of species, citing Dean Herbert's theory that species were created in a plastic state and evolved through intercrossing and variation. He presents evidence from a hybrid tree that bears walnut-like nuts and oak-like leaves, suggesting that all sexual life may have originated from hybrids. The article also discusses Linnaeus's lectures on the animal kingdom, which reveal his deep zoological knowledge and philosophical views. The lectures, collected from notes by students, are accompanied by a commentary and accounts of 123 authors cited by Linnaeus. The lectures show Linnaeus's ability to make scientific topics engaging and practical. The text includes a passage from Linnaeus's Prolegomena, reflecting on the purpose of life and the role of natural history.The book discusses reservoir sites and the use of the microscope and photomicrography. The latter part of the book, which describes various groups of water organisms, has been revised. The plates showing common water organisms have been printed in color, making identification easier. The book is recommended for use in bacteriological and public health laboratories and in the office of the water engineer. John W. Evans criticizes the use of "micromicron" in a translation of Nikitin's work, arguing that it should be "micromillimetre." He explains that "micromicron" would mean a millionth of a micron, a unit useful for expressing intermolecular distances. Newton B. Pierce discusses the origin of species, citing Dean Herbert's theory that species were created in a plastic state and evolved through intercrossing and variation. He presents evidence from a hybrid tree that bears walnut-like nuts and oak-like leaves, suggesting that all sexual life may have originated from hybrids. The article also discusses Linnaeus's lectures on the animal kingdom, which reveal his deep zoological knowledge and philosophical views. The lectures, collected from notes by students, are accompanied by a commentary and accounts of 123 authors cited by Linnaeus. The lectures show Linnaeus's ability to make scientific topics engaging and practical. The text includes a passage from Linnaeus's Prolegomena, reflecting on the purpose of life and the role of natural history.