The geographical distribution of this parasite appears to be a very limited one, as almost all, if not all, of the persons affected, whose cases have been reported, have either been natives of or been long resident on a limited area of the West Coast of Africa, including Congoland and Old Calabar. If Dr. Manson’s view as to the mode of development of the worm be substantiated, then naturally the area of the disease must necessarily be limited to the regions in which the intermediate insect host is to be found. The fully grown worm may, judging by some of the cases recorded, infest the human subject for a good many years, and may yet not give rise to any very serious symptoms. It possesses very considerable locomotive powers. It is capable of wandering at will from one eye to the other, to disappear into the deeper parts of the orbit, to wander under the skin of the eyelids, and even to make excursions in the temporal region. These seem to be the limits of its excursions. No doubt the Rev. Dr. Nassau (the missionary at the Gaboon) had sometimes sensations of a filaria under the skin of the fingers as well as under the skin of the eyelid, but it is doubtful if this was a true case of _Filaria loa_, and even then if the worm had made its way from the fingers to the eyelid. At the same time it must be borne in mind that there are few regions of the body in which the skin is so thin as in the eyelids, whereby the presence of a small filamentous body can easily be discerned. The parasite might readily move about under the coarser cutis of other parts and yet escape detection. The sensitiveness of the parasite to cold appears to be fully established by the experience of my patient and Mrs. H⸺, and it is possible that a prolonged residence in a cool climate may eventually prove fatal to the worm, as seems to have occurred in the case of the Rev. J. L⸺. All the cases previously recorded have occurred in negroes, but those I have brought forward prove that Europeans are also susceptible to the attacks of this worm. I think I am warranted in saying that the disease is not very rare in the district favoured by the parasite, as, although the number of cases reported is small, the irregular intervals at which the worm comes to the surface, and the slight irritation or annoyance its presence causes, often prevent those affected seeking surgical advice; while it must be admitted that medical assistance is not very readily procured in large parts of the district where cases occur. The interest connected with the elucidation of the obscure points in the natural history of the worm will, I trust, stimulate those of our profession residing on the West Coast of Africa to undertake the further necessary investigations. * * * * *