NATURE OF THE DRACUNCULUS, OR GUINEAWORM. 121 
rowing, is frequently imperceptible. This latter portion of the tube is about 31th of an 
inch in length by 5j 55th broad, and continues of much the same size till it terminates 
in a blunt cecal extremity. In a few specimens I have observed the terminal portion of 
the intestine reflected on itself (Pl. XXII. fig. 58). 
Behind the extremity of the intestinal canal, for some little distance, the abdominal 
cavity seems occupied only by bright particles, of irregular size and shape; but then we 
come to the bodies which present a different appearance in different specimens, as before 
mentioned. 
In the form by far the most frequently met with, at the point where the young animal 
begins to decrease in size, a central rounded body may be observed, about 4;;th of an 
inch in diameter, with a dark or light spot in the centre, according to the varying focal 
distance, and which seems to represent a central aperture (Pl. XXII. fig. 57 e). Some- 
times above this traces of two or three large cells may be recognized, whilst behind 
nothing definite can be made out, save that the cavity of the body is visible for about 
z$oth of an inch. 
In other specimens of the young worm the central body and spot are wanting, but in 
its stead two lateral sacculi are met with (Pl. XXII. fig. 59 e, e), about goth of an inch in 
diameter, that communicate with the exterior by a minute channel through the integu- 
ments, which can sometimes be distinctly recognized. At other times the channel is 
obscured by a protrusion, which appears to have taken place through it, of a minute 
bilobed papilla, projecting 45455th of an inch from the side of the body. When the 
projections are seen, the saeculi are indistinct (Pl. XXII. fig. 60). The parts above and 
below are just the same as in the other variety. 
From the extreme rarity with which worms were met with presenting the two lateral 
saceuli, as compared with the multitudes presenting the single central body, I was at first 
disposed to regard the difference as in some way characteristic of different sexes, till con- 
vinced by Mr. Busk that the difference was due only to the position in which the young 
worms were looked at—the central body being one of the lateral sacculi, and the central 
dot its aperture, the former appearing larger in this position than when seen laterally. 
When convinced that this was the correct interpretation, I was at once enabled to explain 
the reason why the double saeculi were so rarely seen; for out of the five specimens of 
the Guineaworm in which the young were more or less coiled, it was the rarest thing 
possible to meet with this form, whilst in the sixth specimen, in which the young were 
nearly all straight, it occurred very frequently. All this is explicable by the supposition 
that the sacculi are situated on the sides of the body, and that the young are constantly 
coiled in one definite direction in the median vertical longitudinal plane of the body em 
that when lying flat they would present one or other side uppermost, showing a single 
central body in the situation mentioned; whilst those which were straight, being at the 
same time cylindrical, would lie indifferently on any part of their circumference, and 
thus sometimes appear with one sacculus only, sometimes with two ; and all intermediate 
positions can be recognized, if carefully sought for. 
What the nature of these sacculi eem be is not very clear. Mr. Busk suggests that 
