6. The character of the changes undergone by the microscopic Filariæ, and the ultimate form assumed by the larvæ whilst still within the body of the intermediate host (_Culex mosquito_), are amply sufficient to establish the genetic relationship as between the embryonal _Filaria sanguinis hominis_, the stomachal Filariæ of the mosquito, and the sexually-mature _Filaria Bancrofti_. In the month of September, 1878, I received a letter from Dr da Silva Lima announcing the fact that Dr Araujo had verified the existence of the embryos of _Filaria Bancrofti_ in mosquitoes, at Bahia. These mosquitoes had, I understood, attacked a French priest in whose blood Dr Araujo also detected Filariæ. Thus, it fell to the lot of Araujo, through his untiring zeal, to verify in Brazil all the separate discoveries of Bancroft, Manson, and Lewis. In the October issue of the ‘Pathological Society’s Transactions’ for 1878 Dr Bancroft records numerous cases of filarious disease, and he gives a succinct account of the circumstances connected with his original discovery. In a clinical lecture published October 12th, 1878, Dr Tilbury Fox seeks to diminish the value of these discoveries, characterising helminthological investigators as merely “recent writers.” Dr Fox denies that Filariæ are a cause of true elephantiasis, but admits the occurrence of “elephantoid inflammation and inflammations due to Filariæ.” Dr Fox’s statement that “Filariæ have not been found in uncomplicated elephantiasis, that is, in disease without chylous exudation,” seems to me to be directly at variance with Manson’s recorded experiences. I hold that Manson has confirmed the truth of Lewis’s views, and that he has thoroughly proved that (to use his own words) “varicose groin glands, lymph scrotum, elephantiasis, and chyluria are pathologically the same disease.” In the first instance I was myself led to conclude that some of the forms of elephantiasis might be due to other causes than obstruction of the lymphatics caused by the presence of Filariæ; but the explanations of Lewis, of Bancroft, and of Manson more especially, have almost entirely removed this doubt. Those who seek to explain away the connection between genuine elephantiasis and Filariæ will do well to study Manson’s last important memoir. He shows that “elephantiasis and allied diseases are much more frequently associated with the parasite than are other morbid conditions.” This fact is brought out very clearly in his table of 670 cases, from which it appears that 58 per cent. of cases of Filaria are associated with elephantoid disease.