embryological series, some of them having their eggs at the back of the gills, between the upper pharyngeals and the branchial arches, others their young in the mouth in different stages of development, up to those a quarter of an inch long and able to swim about, full of life and activity, when removed from the gills and placed in water. The most advanced were always found outside of the gills, within the cavity formed by the gill-covers and the wide branchiostegal membrane. In examining these fishes Mr. Agassiz has found that a special lobe of the brain, similar to those of the Triglas, sends large nerves to that part of the gills which protects the young; thus connecting the care of the offspring with the organ of intelligence. The specimens of this morning seem to invalidate the statement of the fishermen, that the young, though often found in the mouth of the parent, are not actually developed there, but laid and hatched in the sand. The series, in these specimens, was too complete to leave any doubt that in this species at least the whole process of development is begun and completed in the gill-cavity. _October 17th._—Teffé. Yesterday, to our great pleasure, our companions, Mr. James and Mr. Talisman, returned from their canoe expedition on the rivers Iça and Hyutahy, bringing most valuable collections. Mr. Agassiz has felt some anxiety about their success, as, in consequence of their small supply of alcohol, for preserving specimens, which was, nevertheless, all he could spare from the common store, a great deal of judgment in the choice of specimens was required in order to make a truly characteristic collection. The commission could not have been better executed, and the result raises the number of species from the Amazonian waters to more than six hundred, every day showing more clearly how distinctly the species are localized, and that this immense basin is divided into numerous zoölogical areas, each one of which has its own combination of fishes. Our stay at Teffé draws to a close, and to-day begins the great work of packing, in preparation for the arrival of the steamer at the end of the week. These days are the most laborious of all; on leaving every station, all the alcoholic specimens have to be overhauled, their condition ascertained, the barrels, kegs, and cans examined, to make sure that the hoops are fast, and that there are no leakages. Fortunately, there are some of our party who are very dexterous as coopers and joiners, and at these times the laboratory is turned into a workshop. We were reminded of the labors of the day by a circular distributed at breakfast this morning:— “SIR:—The ‘United Coopers’ Association’ will meet in the laboratory after breakfast. You are particularly requested to attend. “TEFFÉ, Oct. 17th, 1865.”