274 



SCIENCE 



[N. S. Vol. XXVII. No. 685- 



A'NOPREL, BREEDING IN 8EA WATER 

 The leading article in the Atti Delia So- 

 cietd per gli Studi della Malaria for 1907 is 

 by Dr. W. T. de Vogel, of Samarang, Dutch 

 East Indies, and is entitled " Anophelines in 

 Sea Water." 



Dr. Vogel shows that the investigations of 

 several Italian workers have negatived the 

 idea that Anopheles can multiply in sea water 

 and that they have shown that the maximum 

 proportion of sodium chloride in the water 

 which Anopheles can stand is 1.87 per cent, 

 according to Perrone, and 1.75 per cent, ac- 

 cording to Vivante. Dr. Vogel, having made 

 some elaborate studies in regard to malaria 

 at Samarang, found as early as 1902 that 

 Anopheles was breeding in a certain pool con- 

 taining 2.8 per cent, of chloride of sodium. 

 Later he verified these results in several inter- 

 esting cases. One of these was the case of 

 the island of Onrust, a small coral island situ- 

 ated two thousand metere from the mainland, 

 and which contains no fresh water whatever. 

 The distance from the mainland is such that 

 even if Anopheles were brought from the 

 mainland by winds they would not be numer- 

 ous enough to cause much trouble. At the 

 same time a marine station established on the 

 island was suppressed on account of the rav- 

 ages of malaria among the workmen. 



He studied also the conditions in the Kari- 

 mon Islands, a little archipelago in the Java 

 Sea sixty-five kilometers from the coast. The 

 first colonists in this archipelago were con- 

 victs and were sent there to cut down the 

 forests of rhizopores. There were no build- 

 ings, and the convicts were forced to sleep on 

 the earth. The mortality was between two 

 and three thousand in two years. Later one 

 of the officers — a man named Michalofski, a 

 plain man but full of good sense — ^sueeeeded 

 in putting a stop to the excessive mortality 

 with the simple means at his disposal, by 

 drying the sea-water pools, completely re- 

 moving a part of the forest, and raising the 

 ground on which the men slept. The success 

 which followed these measures leads Dr. Vogel 

 to suppose that the mortality had been caused 

 by malaria, and this supposition is all the 

 more probable since malaria is to-day rife 



among the population of the islands. He him- 

 self has visited the islands and found much 

 malaria present. The islands themselves are 

 principally flat, planted with cocoanut palms 

 and surrounded by deep water, and again, at 

 a distamee of five hundred or a thousand yards 

 from the coast, by a coral reef. 



There is on the island of Grand Marimon 

 only a single permanent source of fresh water 

 which has only one restricted outlet; so that 

 during the dry season there is no mingling of 

 fresh water with sea water, and there exist 

 during the dry season many pools of dead sea 

 water, peopled with Anopheles larvae, contain- 

 ing not less than three per cent, of sodium 

 chloride, and which then must be considered 

 as concentrated sea water. 



Continuing his researches at Samarang, Dr. 

 Vogel found other pools of water inhabited 

 by Anopheles larvse, in proximity to the sea. 

 One of these places had a surface of 20 to 

 30 square meters and a depth of from 10 to 

 30 centimeters. It was connected with a pool 

 of sea water by a bamboo pipe crossing the 

 dike. The pool is thus invaded by seaweeds, 

 but the fish can not enter. These places 

 swarm with- Anopheles larvae, while Culex 

 larvae are not found there. In this pool the 

 percentage of sodium chloride is about 2.88, 

 while in the water of the neighboring swamps 

 it varies between 2.44 and 2.76. 



Other instances are given with careful de- 

 scriptions and the author finally draws the 

 following conclusions : 



1. There are species of Anopheles which can 

 live very well in sea water. 



2. These mosquitoes lay eggs which develop 

 even in sea water which has been evaporated 

 to half its original quantity. 



3. These larvae in the gradually evaporating 

 pools of sea water can stand an evaporation 

 of the water to one third of its bulli:, but do 

 not appear to transform to adults if the con- 

 centration be greater than this. 



4. The larvae coming from eggs laid in sea 

 water of high concentration can accomplish 

 their entire metamorphoses in almost the- 

 normal time. This is true even when the 

 water has such concentration that the de- 

 velopment of larvae originally hatching in un- 



