MALARIA EXPEDITION TO NIGERIA 
47 
Filaria perstans. 
The embryos of this worm are present in the peripheral blood both day and 
night. The parent forms have been described by Daniel ls, who found them in the 
connective tissues at the root of the mesentery, behind the abdominal aorta and 
beneath the pericardium. The male is smaller than the female. The body is smooth 
and devoid of markings. 
Daniells 1 describes these worms, and compares their lengths and breadths 
with those of the adult forms of F. bancrofti and F. magalbaesi, thus : — 
F. bancrofti F. magalh'desi F. perstans 
Length of female 95 mm. 155 mm. 70 to 80 mm. 
Thickness ,, 0.2 o - 66 otz 
Length of male 44 8 45 
Thickness „ o - io 0-25 o - o6 
The neck is longer than in F. bancrofti : the mouth is very minute ; no 
differentiation of the alimentary canal into oesophagus and intestine could be made 
out. The female tail curves for the last o - 3 to o - 4 mm. Anus OT45 mm. from the 
tip of tail. The tip of the tail is ' mitred.' The embryos in utero are blunt-tailed, 
not sheathed. 
The male is like the female with regard to the head end. Two perfect caudal 
ends were found. They were very much coiled, and had one spicule and two papillae. 
The embryos measure on an average 200 jj. long by 4*6 /x broad: but their 
dimensions vary over considerable range, the embryos possessing to a remarkable 
degree the power to elongate and shorten. They have no sheath. The body tapers 
gradually for two-thirds of its length towards the tail end which is truncated and 
abruptly rounded. On examination of the head with the high powers of the 
microscope, a fang is generally observed, in constant play, protruded and retracted. 
No prepuce is to be made out. The movements of the embryos are extremely 
active, in very fresh preparations it is is almost impossible to follow them as they 
rapidly wriggle about between the corpuscles. Progressive movement continues for 
many hours. 
In stained specimens the embryos of our collection on an average measure 
89 fx. Four spots can be made out : — 
1. A narrow irregular transverse band at distance 2 6 - 4 per cent, of 
total length from anterior end. Nearly always present. 
2. A wider irregular transverse spot at a distance 36. Only occasionally 
present. 
3. The largest of the spots, but not always present ; an irregular 
transverse area at 63*2. 
4. A very inconstant central bright speck at 83*2 distance. 
I. Daniells, British Medical Journal, 1898, vol. I, p. 1011. 
