i9oo] Microscopical journal. 205 



been traced to two species in India and to one in Italy. 

 Other and commoner forms of mosquito, such . as the 

 "brindled" and "grey" mosquitoes, are believed to be 

 quite harmless, if painful, in their bites, though Koch has 

 traced malaria in Tuscany to the bites of Culex pipiens. 

 If this should be filially placed absolutely beyond a doubt 

 it will be of the greatest importance not only to our mil- 

 itary stations and camps, but to many crowded districts, 

 towns and cities. Mosquitoes of the genus Culex breed in 

 artificial collections of water, such as pots and tubs, cis- 

 terns, wells, and drains, but those of the genus Anopheles 

 breed or are developed from larvse or grubs found only in 

 natural ponds and puddles of stagnant water in which 

 green algae are growing, and seldom in larger bodies of 

 water such as tanks or streams, where they would be lia- 

 ble to be devoured by minnows, etc. Still, whether con- 

 fined to the genus Anopheles or not, it seems certain that 

 the flies breed in puddles, and are not of the common or 

 domestic kind. If this be so, and it can be placed beyond 

 question that these mosquitoes breed only in spots suffi- 

 ciently isolated to be dealt with by public measures of re- 

 pression, and that the malaria from which perhaps a large 

 town is suffering can be abated by the filling up or other- 

 wise treating with simple means a few small puddles, we 

 have arrived at a result of investigation that cannot easi- 

 ly be over-estimated. It has already been found for in- 

 stance, that a drachm of paraffin oil poured on the sur- 

 face of a pool about a square yard in area has been suf- 

 ficient to kill all the Anopheles larvse in six hours. It was 

 to solve these matters finally that the Liverpool School of 

 Tropical Medicine sent out its recent well-equipped expe- 

 dition to Sierra Leone, to follow up the work done by Ma- 

 jor Ross in India, and to put the methods suggested to 

 practical proof. Every assistance was given them by the 

 Government, and as we understand that the expedition re- 

 tnrned on October 7th to this country, well satisfied with 



