122 Loa papionis n. sp. 
more than six or seven in the same larva, whereas Fulleborn represents forty- 
one in his diagram. 
The anterior 7 to 10 /x is free from nuclei. In living larvae, a rather re- 
fringent terminal or subterminal granule is often visible at the anterior ex¬ 
tremity, while an oval rather clear area, resembling a vacuole, is frequently 
present immediately behind it. These structures are not individualised in 
stained smears; however, in dried blood-films stained by the panoptic method, 
a central red streak or series of dots is sometimes present in this clear cephalic 
area. 
In unfixed films stained with Giemsa, two pairs of bright-red elongated 
structures are often visible—one pair at each extremity (Plate VIII, figs. 5, 6, 
C.B.). Although Fulleborn describes them in Ml. loa and recommends vital 
staining with azur II and eosin for their demonstration, I never succeeded 
in staining them by this method; I occasionally noticed them, however, in 
dry films after fixation in absolute alcohol and staining with Giemsa. The 
column of body nuclei is separated by a space from the cuticle: the first nuclei 
are frequently situated in the same transverse plane, while the last one reaches 
the tip of the tail or thereabouts. 
The nerve ring and the po.re-cliambers with their pores show nothing 
distinctive; in fresh material examined in a 1 in 2000 solution of azur II in 
0-9 per cent, saline, the stain was observed to enter by the pores as is the case 
in other species. 
The appearance presented by the excretory and genital cells (Plate VIII, 
figs. 2, 3, 4, Ex.c., G.C.) agrees quite closely with the descriptions given by 
Rodenwalt (1908, 1909) and Fulleborn (1913, 1914) for the corresponding 
structures in Ml. loa. The subsidiary genital cells are seldom visible. The average 
position of the more important anatomical landmarks is given in Table I\. 
Table IV. 
» 
Position of the more important anatomical landmarks expressed in percentages 
of the body length. 
Middle of nerve ring 
20-3 
Excretory pore 
30-3 
Nucleolus of excretory cell 
34-3 
Nucleolus of first genital cell 
66-5 
Anal pore 
81-7 
In dry blood-films stained by the panoptic method, a fail spot is usually 
present immediately behind the place where the last two nuclei occur abreast 
(Plate VIII, fig. 1, T.S.). 
The central viscus (Plate VIII, figs. 1, 2, 3, C.V.) is present in a fair propor¬ 
tion of the larvae and is often visible in living unstained ones. It lies a short 
distance in front of the first genital cell and varies up to 45/x in length. In dried 
