METAMORPHOSIS OF FILARIA BANCROFTI, COBB. 49 



and of course the scepticism of so eminent an authority is of great 

 weight in influencing opinion, especially in Germany." 



In answer to an inquiry from me as to whether there was any 

 recent work on the subject of " filarial metamorphosis," Dr. 

 Manson wrote, November 15th, 1898: — "So far as I know, 

 nothing has been done in "filarial metamorphosis" since ray 

 Linnean Society's paper. Lewis did not go very far with the 

 work. There is an excellent opportunity for work on this subject, 

 and were I in your place, I should certainly go on with it." 



In writing to Dr. Manson, I had mentioned the circumstance 

 of my being able to verify his "filarial metamorphosis," but that 

 I had never seen the "actively moving filaria," which he stated 

 left the mosquito's body and lived a free life in water until trans- 

 ferred to the human host. 



To this he replied in these words : — "I have seen the "actively 

 moving filaria " in the seven days' old mosquito a good many 

 times ; I used to be able to pick out the mosquitoes containing it. 

 Their thoraces looked plump and juicy to the eye. Of course you 

 must have hundreds of mosquitoes from which to select such." 



Now in my former investigation there was no difficulty in find- 

 ing the early stages of the metamorphosis in every mosquito 

 (Culex ciliaris) without exception, which had imbibed filariated 

 blood ; those mosquitoes which lived seven days — and none ever 

 lived longer — never contained any actively moving filarise ; they 

 contained forms more or less resembling Figure 4. 



It were useless to make further search for this " actively moving 

 filaria"; either Manson must be in error I thought, or the Culex 

 ciliaris was not an efficient host. 



The recent work in India on the metamorphosis of the Malarial 

 parasite in mosquitoes induced me to study the habits of these 

 insects in this district. I found that I could keep certain kinds 

 of mosquito, particularly Culex ciliaris and a large black species 

 hitherto undescribed, alive in confinement for about two months; 

 one individual actually lived seventy dnys. Banana was found 



D— June 7, 1899. 



