18 Prof. J. C. Schiddte on the Structure of 
situated; this latter consequently projects downwards inside 
the mouth-tube, just behind the labrum, and beneath the 
corresponding lobe of the tongue, which forms the bottom of 
the mouth-tube. The lobe of the mandible (m, fig. 4c) is 
elongated triangular, gradually acuminated, with convex back 
and concave front, the sharp lateral edges meeting at the 
sharp-pointed hooked apex. ‘The muscles of the lobe fill the 
greater part of the stem in front of the insertion of the palpus. 
This arrangement, in connexion with the corresponding great 
length of the stem, indicates great power and perseverance of 
movement, and explains how these lobes, in spite of their 
inconsiderable size, may be used with great effect. ‘Their 
shape and position enables the animal to sink them into its 
victim, one from either side, in slanting converging directions, 
and then, by drawing them back simultaneously with sufficient 
strength, to tear out the piece which les between them. That: 
they are destined to work against each other and to be drawn 
back together is plain from the circumstance that their points 
are not quite uniform, the left hook being somewhat more bent 
than the right one, and at the same time a little twisted to the 
side, so that it can take hold round the other. 
The sawing-styles, or maxilla of the first pair, consist each of 
a shorter stem and a longer lobe, which joins the former evenly 
allround, ‘They are hard, smooth, slightly flattened, and bent 
inwards, so that their ends project downwards in the mouth- 
tube, behind the mandibular lobes, under the tongue, and on 
either side of the buttonhole-shaped sucking-slit. The seven 
hooked spines at their apex are so placed as to form a curved 
group; and it is therefore difficult to make out their form and 
number except when the lobe is pressed.. These sawing-styles 
are evidently intended to act as auxiliary instruments, for 
deepening, increasing, and lacerating the wounds made by the 
mandibular lobes. 
The long and slender mandibular palpi (fig. 4a) are, when 
at rest, placed firmly against the head in a. groove on the 
underside of the skull, which runs at a little distance from the 
stem forwards between the forehead and the posterior antenne, 
round the basal joint of which their pointed and sickle-shaped 
terminal joint coils itself. The palpi, being inserted so. far he 
hind and to the side that they have considerable room for play, 
are probably destined for thahing the mouth-tube with the 
brush at their apex, and to comb away the fishy slime from 
the marginal hooks by means of the fine comb of spines im- 
planted in the outer margin of the terminal joint. 
The structure of the mouth in 4ga may therefore be de- 
scribed in the following terms :— ks 
