146 ON THE " MILLIONS " FISH AND MALARIA. [Fel).l, 



February 1, 1910. 



Prof. E. A. Minchin, M.A., Vice-President, 

 in the Chair. 



Mr. Charles A. Darling, General Manager of the British New 

 Guinea Development Co., exhibited a mounted specimen of a 

 discus [Phcdanger maculatus). The animal had been captured in 

 New Guinea and brought to England alive, but had subsequently 

 died, and was to be presented to the British Museum (Natural 

 History) by its owner, Mr. D. Elliot Alves. Mr. Darling called 

 attention to the soft white fur with brown spots and the prehensile 

 tail, and stated that when the living animal was asleep in daylight 

 the eyes remained open with the pupils fully contracted. 



Malaria and the " Millions " Fish (Girardinus pceciloides). 



The Secretary read the following letter which he had received 

 from Captain J. A. M. Vipan, F.Z.S. : — 



" During the last eighteen months a great deal has been said 

 regarding the absence of fever in Barbados and the cause of this 

 immunity, which has rightly been put down to the presence in 

 great numbers of a little fish, Girardinus pceciloides, locally known 

 by the name of Millions, which feeds on water crustaceans a,nd 

 insects including the larvae of the mosquito, and from being in 

 such vast numbers, very effectively keeps down this insect and 

 consequently malaria. Now the reason of this little fish being 

 found in such vast quantities all over the island of Barbados is 

 not difficult to state, for it happens to be the only fresh-water 

 fish on the island and consequently has no enemies in the fish 

 line to reduce its numbers. 



" In the island of Trinidad, where there is a certain amount of 

 fever, there is another little fish. Girardinus gitppii, but in restricted 

 numbers, as there are plenty of other and larger fishes in the fresh 

 waters that keep it from multiplying to any great extent. 



" On the mainland in Venezuela where fever is rife, there is also 

 a little Cyprinodont, Poecilia reticulata Peters, but there are also 

 great quantities of other fishes. 



" These three little Cyprinodonts — G irardinus pceciloides, Girar- 

 dinus guppii, and Pcecilia reticulata — I have kept for some years 

 in an aquarium, and I have found that they all interbreed freely 

 and am quite sure they are all the same species under different 

 names. 



" That being so, and the fact that in Venezuela and Trinidad, 

 where these fishes are indigenous, there is an abundance of fever, 

 what can be the use of expending large sums of money in 

 importing some of these little fishes to other fever- stricken countries 

 such as Nigeria, for even supposing they survive the attacks of 

 other fish, how could an importation of a few hundreds or 

 thousands be of any use in the great watershed of the Niger ; 



