3d. I saw you take the urine of a female patient suffering from ague (though from motives of delicacy I did not see the urine voided--still I believe that she did pass the urine, as I did not think it necessary to insult the patient), and you demonstrated to me beautiful specimens of Gemiasma rubra. You said it was not common to find the full development in the urine of such cases, but only in the urine of the old severe cases. This was a mild case. 4th. I saw you take the blood from the forearm of an ague patient, and under the microscope I saw you demonstrate the gemiasma, white and bleached in the blood. You said that the coloring matter did not develop in the blood, that it was a difficult task to demonstrate the plants in the blood, that it required usually a long and careful search of hours sometimes, and at other times the plants would be obtained at once. When I had fully comprehended the significance of the experiments I was filled with joy, and like the converts in apostolic times I desired to go about and promulgate the news to the profession. I did so in many places, notably in New York city, where I satisfactorily demonstrated the plants to many eminent physicians at my room at the Fifth Avenue Hotel; also before a medical society where more than one hundred persons were present. I did all that I could, but such was the preoccupation of the medical gentlemen that a respectful hearing was all I got. This is not to be wondered at, as it was a subject, now, after the lapse of nearly a decade and a half, quite unstudied and unknown. After this I studied the plants as I had opportunity, and in 1877 made a special journey to Long Island, N.Y., for the purpose of studying the plants in their natural habitat, when they were in a state of maturity. I have also examined moist soils in localities where ague is occasionally known, with other localities where it prevails during the warm months. Below I give the results, which from convenience I divide into two parts: 1st. Studies of the ague plants in their natural habitat. 2d. Studies of the ague plants in their unnatural habitat (parasitic). I think one should know the first before attempting the second. _First_--Studies to find in their natural habitat the palmellæ described as the Gemiasma rubra, Gemiasma verdans, Gemiasma plumba, Gemiasma alba, Protuberans lamella. _Second_--_Outfit_.--Glass slides, covers, needles, toothpicks, bottle of water, white paper and handkerchief, portable microscope with a good Tolles one inch eyepiece, and one-quarter inch objective.