medinensis_ (guinea-worm), which was introduced times without number during the days of slave importation into the West Indies, yet it has died out altogether except in one or two places, the island Curaçao and a limited district in Brazil. This undoubtedly is in consequence of one of two things; either the habits of the people, or the absence of the proper intermediate host. In respect of the guinea-worm the intermediate host is a fresh-water cyclops. I recently had a case in the Seamen’s Hospital from which I was enabled to procure the embryos. This enabled me to carry out some experiments which I would urge upon those who have the opportunity to repeat. When the guinea-worm arrives at maturity a little vesicle or bulla is formed on the ankle or foot. The vesicle ruptures, and on careful examination you will see a small orifice in the centre in which sometimes the head of the worm may be seen, but not always. If you take a sponge and drop some cold water, not on, but in the neighbourhood of this orifice, you will see the hole become filled with a white grumous material, which under the microscope, and on adding a little water, is seen to be a wriggling, writhing mass of embryos. The application of water to the leg after an interval may lead to further extrusion of embryos. This is a striking illustration of the curious way nature has adapted the habits of the guinea-worm to its requirements. The young guinea-worm lives in water, and probably for this reason the mature worm descends to the feet or ankles, the parts of the human body in tropical countries most often within reach of water. Having procured in this way a supply of embryos, I tried to repeat the experiment described by the Russian naturalist, Fedschenko, on the metamorphosis of the embryos of the guinea-worm in its intermediate host. I obtained some fresh-water cyclops and placed them in water with the embryos. After five or six hours I took one of the cyclops and placed it under the microscope, and I found the body-cavity to contain twenty or thirty of the living and moving embryos. The next day, however, the cyclops were all dead, but the contained embryos were all lively. Having still one or two of the cyclops left I repeated the experiment, but, proceeding more cautiously, placed only a few of the embryos in the water along with the cyclops. After a few hours I removed the cyclops, and found that each of them had two or three guinea-worm embryos coiled up or moving about in their insides. Two of the cyclops I kept alive; one lived sixteen days and the other five weeks, and during this time the embryos could be seen moving and developing. At the end of five weeks I killed the cyclops, and I found the guinea-worm embryos had undergone a certain degree of development. The outer cuticle of the embryo had separated a good deal from the body—ecdysis, and there were certain changes in the alimentary canal. I have no doubt that had the cyclops been in a normal