The scrapings of the soil showed beautiful yellow and transparent Protuberans, beautiful green sporangias of the Gemiasma verdans. Observation 5. Near the brook named was a good specimen of the Gemiasma plumba. While I could not find out from the lay people I asked that any ague was there, I now understand it is all through that locality. Observation at Wellesley, Mass., Aug. 20, 1877. No incrustation found. Examined the vegetation found on the margin of the Ridge Hills Farm pond. Among other things I found an Anguillula fluviatilis. Abundance of microspores, bacteria. Some of the Protococci. Gelatinous masses, allied to the protuberans, of a light yellow color scattered all over with well developed spores, larger than those found in the Protuberans. One or two oval sporanges with double outlines. This observation was repeated, but the specimens were not so rich. Another specimen from the same locality was shown to be made up of mosses by the venation of leaves. Mine host with whom I lodged had a microscopical mount of the Protococcus nivalis in excellent state of preservation. The sporangia were very red and beautiful, but they showed no double cell wall. In this locality ague is unknown; indeed, the place is one of unusual salubrity. It is interesting to note here to show how some of the algæ are diffused. I found here an artificial pond fed by a spring, and subject to overflow from another pond in spring and winter. A stream of living water as large as one's arm (adult) feeds this artificial pond, still it was crowded with the Clathrocyotis æruginosa of some writers and the Polycoccus of Reinsch. How it got there has not yet been explained. The migration of the ague eastward is a matter of great interest; it is to be hoped that the localities may be searched carefully for your plants, as I did in New Haven. In this connection I desire to say something about the presence of the Gemiasmas in the Croton water. The record I have given of finding the Gemiasma verdans is not a solitary instance. I did not find the gemiasmas in the Cochituate, nor generally in the drinking waters of over thirty different municipalities or towns I have examined during several years past. I have no difficulty in accounting for the presence of the Gemiasmas in the Croton, as during the last summer I made studies of the Gemiasma at Washington Heights, near 165th St. and 10th Ave., N.Y. Plate VIII. is a photograph of a drawing of some of the Gemiasmas projected by the sun on the wall and sketched by the artist on the wall, putting the details in from microscopical specimens, viewed in the ordinary way. This should make the subject of another observation.