383 



2. Enclosed in a sheath considerably longer 

 than body of embryo. 



3. If placed rapidly beneath microscope shews 

 at first active progressive movement (Annett and 

 Button), later the anterior tip of the sheath ap- 

 pears to become attached to the glass, and move- 

 ments of the embryo, though active, are not pro- 

 gressive. 



4. The embryo shews an anterior abruptly 

 rounded off end and a posterior, tapering for two- 

 fifths the length. There is a six-tipped prepuce 

 and a short very fine fang. 



5. The stained specimen shews (i) an irregular 

 transverse break about twenty-one per cent, of the 

 length. 



(ii) A V-shaped spot or transverse irregular 

 break at a distance of about thirty per cent, of the 

 length from anterior end. Nearly always present. 



(iii) An area of varying length with cells 

 loosely arranged, sixty-three per cent, length. 

 This is constant and represents the central ag- 

 gregation of fresh specimens. 



(iv) An irregular, sometimes oval spot, often 

 present, eighty-five per cent, length. 



(v) A small central bright spot occasionally, 

 ninety-one per cent, length. 



F. dturna. — No differences are distinguish- 

 able between the embryos of F. diurna and 

 F. nocturna either ini the fresh or stained specimen 

 (Annett and Button). Button and Annett 

 have found the embryos taken from the adult 

 female F. loa to be practically identical with those 

 of F. diurna, and describe a case in which infec- 

 tion with F. loa was associated with embryos 

 present in the blood during the day and not to 

 the same extent at night. 



