naturally infest thorn. This determination has its practical as well as its scientific value, for it enables us to eliminate certain non-pathogenic parasitic organisms from the life cycle of pathogenic organisms, stages of which may be found in mosquitoes. It further has its direct practical bearing in that the parasites of mosquitoes may multiply to such an extent as to become important factors in killing the insects, or at least in rendering them less fertile.
He also refers to a similar Agamomermis, which he found in mosquitoes in Leipzig and which, according to Leuckart, seems to have an influence in decreasing the numbers of mosquitoes. Finally Dr. Stiles says: "These cases represent interesting instances in nature, where a pest is subject to other pests which tend to hold the former in check."
We do not find in the article any suggestion that the Public Health Service is breeding these worms for practical purposes, as intimated by the Sun, in order to kill mosquitoes. In fact, it would take considerable study to determine whether such a plan would be practicable. If this parasite could be bred artificially in sufficient numbers it is by no means an impracticable proposition to utilize them to destroy mosquitoes in regions where the use of kerosene is difficult or impossible. We do not, however, gather from the article the impression that the service proposes any such plan at present. In fact, we can see technical difficulties in the way which would make the method rather expensive, and it would, at most, be applicable only under certain conditions. We can not, therefore, hold out any great hope that Agamomermis culicis, which the New York Sun has named the 'mosquito destroyer,' presents to us at present a substitute for kerosene and proper drainage. But we share the view expressed in the original article that this represents 'a case of parasitism of considerable interest' and that parasites of mosquitoes, like parasites of other animals, 'may multiply to such an extent as to become important factors in killing the insects, or at least in rendering them less fertile.'
RADIUM IN ENGLAND.
That marvelous substance radium, some account of which was published in the Popular Science Monthly for July, 1900, and June, 1903, still attracts the attention of both men of science and laymen throughout intellectual nations. In London recently the luminescent property of the rays issuing from the element was shown to King Edward and Queen Alexandra, on the occasion of their visit to the London Hospital, and the penetrating power of the rays was also demonstrated by the following: A pile of six pennies was placed over a small piece of radium and the light emitted was visible through the coins.
At the Museum of Natural History, London, the director has arranged a little exhibition with a view to giving the public an opportunity of seeing the material and some of its interesting properties. Its source is shown in
