PART III.] Development of Hcematozoa in the Mosquito. 621 



a similar result was observed by Fedschenko to follow the ingestion of dracunculus- 

 embryos in the stomach of the Gyclojps. The latter is believed to serve as an inter- 

 mediary host for the development of the guinea-worm, the embryos getting into the 

 body of the Cyclops by piercing the cuticle. When the embryos are swallowed they 

 are digested. 



In the course of the foregoing observations it was observed that all the mosqui- 

 toes captured in one of the servants' houses contained hsematozoa of the same character, 

 and it was found that one of the five persons dwelling in this house harboured filarise 

 in his blood. The man had been many years in the place and is not known to have 

 suffered from any special disease. 



The circumstance of such a constant supply of filarious mosquitoes, of tolerably 

 certain history, materially simplified the course of investigation, which, briefly told, was 

 as follows : — 



Insects were caught early in the morning in the room in which this person had 

 slept, just as Dr. Manson had done. Some were placed in bell glasses standing in 

 water, others in test-tubes containing a little water at the bottom and covered with 

 a strip of muslin. These were duly labelled and set aside for periodical examination. 



When the insect was examined with recently ingested blood in its stomach, it 

 was found that the hsematozoa, when present, did not differ materially from the aspect 

 presented by them when extracted directly from blood of its previous host (Plate XLII, 

 Fig. 5), although, not unfrequently, parasites would also be seen which either belonged 

 to a more advanced stage of the one under consideration, the result of a previous 

 ingestion of filarious blood, or belonging to a totally different kind. There is always, 

 therefore, a risk of confusing different parasites in the same insect. Kepeated examina- 

 tions at the same periods tend, however, to minimise this source of errror. During 

 the first twenty-four hours no marked change takes place in the form of the organisms. 



On the second day, however, it will probably be seen that the blood has, to a con- 

 siderable extent, undergone digestion, and the stomach will no longer manifest the 

 distended condition of the first day. Probably a few altered hsematozoa will be observed 

 in it moving very languidly, presenting the appearance of partially disintegrated fungal 

 filaments when the movements are not manifested. Some of them may be actually 

 dead ; these will be found to be stained by eosin solution very readily. 



Between the second and the third day further changes occur, but in order to be 

 able to follow these it will be necessary to examine the other tissues of the insect, as 

 possibly the stomach may contain none ; it will, however, probably be found that some 

 of them have migrated into the tissues immediately outside this viscus. It will now 

 be observed that some of the parasites have become considerably thicker (Fig. 7) ; and 

 occasionally specimens will be seen with the tail presenting the appearance of a lash 

 (Fig. 9) ; the movements are still very sluggish. 



.About the fourth day it is probable that examples in various stages of growth 



