92 T. R. Lewis — Hsematozoa in Stomach, of Cnlex Mosquito. [MARCif, 



examinations under these favourable conditions has shown that although the 

 stomach digests a great number of the ingested hsematozoa, as mentioned 

 above, nevertheless others actually perforate the walls of the insect's stomach, 

 pass out, and then undergo developmental stages in its thoracic and abdo- 

 minal tissues. Although I cannot say as a result of actual observation 

 that the links connecting the various earlier phases of the development are 

 complete, nevertheless they appear so near to being so that it may, I think, 

 be confidently anticipated that observers in this country will soon be able 

 conclusively to satisfy themselves that, in most particulars at least, Dr. 

 Manson's valuable observations apply to India as well as to China. 



With regard, however, to the inference that the mosquito is the parti- 

 cular intermediary host of nematoid hsematozoa, it cannot be said that even 

 these later observations are sufficiently conclusive to warrant a positive 

 statement being made at present, for, though assuming that of the various 

 parasitic forms which have been seen, several are actually transitional stages 

 in the development of one and the same entozoon, it is to be noted that 

 even the most advanced stage hitherto observed is still a very immature 

 one — no trace of reproductive organs, for example, being distinguishable ; 

 and every attempt hitherto made by myself to obtain a more advanced 

 condition has proved unsuccessful. Further observation, however, may 

 overcome or explain this want of success. 



It should be added that the blood of one of the five persons who were 

 in the habit of sleeping in the house in which these particular insects were 

 captured, was found to contain hsematozoa in considerable numbers. T.R.L.] 



Dr. McLeod observed that the subject of Dr. Lewis's paper was one of 

 very deep interest, inasmuch as the diseases attributed to, or associated with 

 the presence of, immature filarim in the blood are very serious, and, if the 

 mosquito is the agent of their dissemination, everybody living in countries 

 infested by mosquitos, is more or less liable to them. The theory of the 

 mosquito being an intermediary agent of the develoiDment of Filaria san- 

 guinis-hominis has been laid down in very plain and positive terms. It is 

 satisfactory to find that, so far as observations made in India have hitherto 

 gone, instead of undergoing development in the mosquito's stomach, 

 these hsematozoa undergo digestion. The only weak point which occurred 

 to him in Dr. Lewis's observations was that the animals were kept for 

 observation in more or less artificial conditions, and not allowed access to 

 water, which is alleged to be an important medium of the development of 

 these JilaricB. 



There is no question now that these animals exist in the mature state 

 in the human tissues and in the immature state in human blood. How 

 they gain access to the body originally is unknown. Given the mature 



