Leydig (Lehrbuch der Histologie, p. 467) long ago stated that the green gland consists of a much convoluted tube containing granular cells disposed around a central cavity. Wassiliew (“Ueber die Niere des Flusskrebses:” Zoologischer Anzeiger, I. 1878) supports the same view, giving a full account of the minute structure of the organ, and comparing it with its homologues in the _Copepoda_ and _Phyllopoda_. NOTE X., CHAPTER III., p. 105. THE ANATOMY OF THE NERVOUS SYSTEM OF THE CRAYFISH. The details respecting the origin and the distribution of the nerves are intentionally omitted. See the memoir by Lemoine of which the title is given in the “Bibliography.” {354} NOTE XI., CHAPTER III., p. 110. THE FUNCTIONS OF THE NERVOUS SYSTEM OF THE CRAYFISH. Mr. J. Ward, in his “Observations on the Physiology of the Nervous System of the Crayfish,” (Proceedings of the Royal Society, 1879) has given an account of a number of interesting and important experiments on this subject. * * * * * NOTE XII., CHAPTER III., p. 124. THE THEORY OF MOSAIC VISION. Oscar Schmidt (“Die Form der Krystalkegel im Arthropoden Auge:” Zeitschrift für Wissenschaftliche Zoologie, XXX. 1878) has pointed out certain difficulties in the way of the universal application of the theory of mosaic vision in its present form, which are well worthy of consideration. I do not think, however, that the substance of the theory is affected by Schmidt’s objections. NOTE XIII., CHAPTER III., p. 135. THE SPERMATOZOA.