1900.] on Malaria and Mosquitoes. 9 



next detected within each of these cells a few granules of the character- 

 istic coal-black melanin of malarial fever a substance quite unlike 

 anything usually found in mosquitoes. Next day the last of the 

 remaining spotted-winged mosquitoes was dissected. It contained 

 precisely similar cells, each of which possessed the same melanin; 

 only the cells in the second mosquito were somewhat larger than those 

 in the first. 



These fortunate observations practically solved the malaria 

 problem. As a matter of fact, the cells were the zygotes of the 

 parasite of remittent fever growing in the tissues of the gnat ; and the 

 gnat with spotted wings and boat-shaped eggs in which I had found 

 them belonged (as I subsequently ascertained) to the genus Anopheles. 

 Of course it was impossible absolutely to prove at the time, on the 

 strength of these two observations alone, that the cells found by me 

 in the gnats were indeed derived from Haomamoebidse sucked up by 

 the insects in the blood of the patients on whom they had been fed 

 this proof was obtained by subsequent investigations of mine ; but, 

 guided by the presence of the typical and almost unique melanin in 

 the cells, and by numerous other circumstances, I myself had no 

 doubt of the fact. The clue was obtained ; it was necessary only to 

 follow it up an easy matter. 



The preparations of the stomachs of the two Anopheles were 

 sealed, and were afterwards examined by Drs. Smyth, Mauson, Thin 

 and Bland-Sutton ; and an account of the work, and of the observa- 

 tions of these gentlemen, was published a little later. Unfortunately, 

 my labours now met with a serious interruption ; but not before I 

 had succeeded again in finding the zygotes in two other mosquitoes 

 one, another species of Anopheles, also bred from the larva, and also 

 fed on a case containing crescentic gametocytes ; the other, a " grey 

 mosquito " (Culex pipiens type), which had been caught feeding on a 

 case of tertian fever, and which I now think had become previously 

 infected from a bird with Hsemamasba relicta. 



Early in 1898, mainly though the influence of Dr. Hanson, Sir 

 H. W. Bliss and the United Planters' Association of Southern India, 

 I was placed by the Government of India on special duty in Calcutta 

 to continue my investigations. Unable to work with human malaria 

 chiefly on account of the plague scare in Calcutta I turned my 

 attention to the Hsemamoebidae of birds. Birds have at least two 

 species of Heeniauicebidae. I subjected a number of birds containing 

 one or the other of these parasites to the bites of various species of 

 mosquitoes. The result was a repetition of that previously obtained 

 with the human parasites. Pigmented cells precisely similar to those 

 seen in the Anoplieles were found to appear in gnats of the species 

 called Culex fatigans, Wiedemann, when these had been fed on 

 sparrows and larks containing Hsemamceba relicta. On the other 

 hand, these cells were never found in insects of the same species when 

 fed on healthy birds or on birds containing the other parasite, called 

 Hsemamceba danilewskii. 



B 3 



