criticism of a theory, one expects at least an equally good explanation to be put forward ; but that had not been done, and on examining the paper one found that Dr. Prout went no further than to say that these diseases might be due to something else ; there was no definite suggestion substituted for the filarial hypothesis. Dr. Prout further stated : " The coincidence between the geographical distri- bution of endemic elephantiasis and F. hancrofti is claimed as being one of the most important proofs of the connection between the two, and it is maintained that where F. nocturna is common, there elephantiasis is common, and vice versa. Now, the coincidence of the geographical distribu- tion of elephantiasis and F. nocturiia simply means that both are found universally over the Tropics." He disagreed entirely with the latter part of that statement. The author, apparently, had worked only, or chiefly, in Sierra Leone, and had not examined similar conditions in other parts of the world. Personally, he knew of places in the Tropics where there were practically no filariae. For instance, in the denizens of the forests of British Guiana no F. nocturna was found — at least, he had never found that infection, and Dr. Daniel's experience was the same. He had made many hundreds of blood examinations of Waganda — the natives of Uganda proper — but he never found F. nocturna. So that there were at least two places in the tropical world where F. nocturna was non-existent. And if natives of those two districts were collectively examined, it would be found that neither elephantiasis nor any of the other filarial diseases occurred there. He had seen elephantiasis in Entebbe, but the people who suffered from the disease were not indigenous, they were natives of the Soudan, in whom F. nocturna was common. One of the most important premisses on which the author's con- clusions were based thus fell to the ground. The next point to which he desired to refer was the statement that
