MALARIA EXPEDITION TO NIGERIA 29 
The anterior end resembles that of the female but is smaller. The oesophagus is 
o - 57 mm. long (in one very transparent specimen only, a distinct cardiac constriction 
could be made out). The anal orifice is at a point o - o8 mm. from the tip nt the tail 
(plate III, figs. 1 and 2). Four pre-anal and three post-anal papillae on each side could be 
made out; the two last post-anal being very small. The genital orifice is in the median 
line at the apex of a slight raised prominence. On each side of this prominence are 
two cuticular expansions, bearing the papillae and forming continuations ot the lateral 
cuticular ridges. There are two curved unequal retractile spicules, the ventral of which, 
shorter than the dorsal, appears to be hollowed out on its dorsal surface for the latter' s 
reception. The dorsal spicule is rod shaped and ends in a round knob. The other 
seems to widen at its deeper end and bends round the sides ot the dorsal. The 
spermatic canal runs up the worm from the neighbourhood of the base of the spicules 
as a single narrow tube which soon widens to fill up almost the whole of the body 
cavity. A short distance from the head it becomes somewhat narrower, and ends after 
making a few turns in this region. 
The embryos are found in large numbers in the peripheral and in the heart's 
blood. They have a sheath which is a long narrow cylinder with rounded ends. 
In fresh specimens the embryos exhibit a simple snake-like lashing movement, pro- 
gressing forwards and backwards, and also a backward and forward motion inside the 
sheath. Some were seen to coil themselves up closely. The worm with its sheath 
(plate XIII, fig. 2) has a uniform thickness, except at the posterior end where it suddenly 
diminishes into a wall-marked ' tail.' The length ot the worm inside the sheath was 
2o8 - 6 /u, breadth 1*7 In the living specimens two longitudinal lines ot fine refractile 
granules can be observed, one about the junction of the anterior and middle thirds, 
the other about the junction of the middle and posterior thirds. The head end is 
rounded, no definite prepuce nor spine could be made out, beyond a highly refractile 
'glans'-like tip. At the tail end the width of the worm suddenly diminishes at a 
distance of about 6-5 /a from the extreme tip to about 2 /*. The tail comes off 
eccentrically. 
In stained specimens (plate III, fig. 5) no characteristic position is acquired. 
The average length of the worm, which varies considerably, is 2 1 6*8 M . The column of 
small nucleated cells forming the body, at the head end is bayed out so that the end 
appears bifid. Five ' spots ' (V- or otherwise-shaped) can be made out ; their 
numbers however varies from three to five. 
On examination of a number of embryos the distances of the spots from the 
end of the worm relatively to its length proves to be fairly constant, and we shall 
adopt throughout this work a method similar to Cobb's to indicate their positions ; 
expressing the distances of the middle of the spots from the anterior end in per- 
centages of the total length : 
1. A transverse slit : distance 24-5 per cent, of length ; sometimes not seen. 
