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Long ago it was recognized by scientists that heat is an essential factor in the development of the germ and formation of the embryo. Moreover, the embryo can develop normally only within certain limits of temperature.From experiments with the influence of temperature on the developing chick embryo ( Gallus domesticus) Pr6vost and Dumas (1825) found that the temperature between 30" and 40°C. is suitable for artificial incubation. Later, Dareste (1891), in his famous book, "RQcherches sur la production artifici6lle des monstruositk, ' ' stated that normal incubation temperature must be between 35" and 39°C. Below or above these limits, as he thinks, there mould invariably be production of monsters and somewhat similar anomalies marked by anemia of the embryo. Then FQr6 (1894), in a study of the early development of the embryo under various temperatures, concluded that 38°C. is the most appropriate temperature f o r the development of the chick embryo at that period.More recently, Henderson and 13rody ('27) and Henderson ('30) well demonstrated that at continuous exposures to temperatures ranging from 34.4" to about 41.7"C. the growth of the embryo and its nitrogen content are profoundly influenced by temperature. 457

WATER chlorination practice has evolved, during the past fifty years, from a relatively crude application to a highly efficient one. Such a steady process of progressive change is characteristic not only of this practice, but of all applications of scientific knowledge. The results of chlorination can be evaluated on the basis of the chemical and bacteriological results which have been accomplished by its use, and, for this purpose, it will be helpful to review briefly the history (1) of this method of water treatment.

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The aim of the AWWA Research Foundation in this study is to evaluate major desalting techniques electrodialysis, ion exchange, and reverse osmosis. Emphasis is on methods of providing the public with economical, high-quality water.