THE INTERMEDIARY HOST OF FILARIA CYPSELI 147 
through the agency of Anopheles maculipennis, and it is probable that F. bancrofti is 
transmitted in a similar way from man to man. It is quite possible that infection of 
the swifts may take place by both of the above methods. 
The points of interest associated with this filaria are : — 
1. Up to the present it has only been found in one species of bird, 
Cypselus <iffinis, while other African bird filariae are generally 
encountered in many different species. 
2. The habitat of the embryo is essentially the lymph. 
3. The louse which acts as its intermediate host, as a general rule, belongs 
to a family, the members of which usually, though not always, 
are parasitic on one species of bird only. 
4. This louse does not exclusively feed on feathers, but sucks up blood, 
and probably to a greater extent lymph. 
5. The metamorphosis of the parasites is very similar to that of previously 
known filariae. 
In conclusion, I must thank Dr. H. E. Annett for the kind interest he has 
shown in this study and for the help and suggestions he has given me. 
EXPLANATION OF PLATE 
Semi-Diagrammatic 
Embryo of F. cypseli as seen in lymph of swift ( x 300). 
First stage in development in body of louse ( x 300). 
Second stage „ „ „ ( X 300). 
Showing development of mouth opening ( x 300). 
Showing differentiation of body into inner and outer layer and commencing striation. 
Stage III. Optical median section of parasite ( x 300). 
Stage IV. 
Stage V. „ „ „ „ 
Embryos seen in lining tissue of abdominal cavity of louse ( x 150). 
Intermediary host of Filaria cypseli, sub-family Leiothinae sp. incert. 
